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. 2020 Mar 26;15(3):e0230877. doi: 10.1371/journal.pone.0230877

Effect of custom-made and prefabricated foot orthoses on kinematic parameters during an intense prolonged run

Marina Gil-Calvo 1,#, Irene Jimenez-Perez 1,2,*,#, Jose Ignacio Priego-Quesada 1,2,#, Ángel G Lucas-Cuevas 1,#, Pedro Pérez-Soriano 1,#
Editor: Alena Grabowski3
PMCID: PMC7098605  PMID: 32214390

Abstract

Foot orthoses are one of the most used strategies by healthy runners in injury prevention and performance improvement. However, their effect on running kinematics throughout an intense prolonged run in this population is unknown. Moreover, there is some controversy regarding the use of custom-made versus prefabricated foot orthoses. This study analysed the effect of different foot orthoses (custom-made, prefabricated and a control condition) on spatio-temporal and angular (knee flexion and foot eversion) kinematic parameters and their behaviour during an intense prolonged run. Twenty-four recreational runners performed three similar tests that consisted of running 20 min on a treadmill at 80% of their maximal aerobic speed, each one with a different foot orthosis condition. Contact and flight time, and stride length and stride rate were measured every 5 min by an optical measurement photoelectric cell system. Knee flexion and foot eversion kinematic parameters were measured by two high-speed cameras. No significant differences were found between the different foot orthoses in any of the time points studied and between the interaction of foot orthosis and behaviour over time, in any of the variables studied (P > 0.05). The use of custom-made and prefabricated foot orthoses during an intense prolonged run does not produce changes in spatio-temporal and kinematic parameters in healthy runners. These results suggest that a healthy runner maintains its ideal movement pattern throughout a 20 minute prolonged run, regardless the type of foot orthosis used.

Introduction

Running is one of the most popular recreational and competitive physical activities due to its health benefits [1]. However, injury risk in the lower limb is also relatively high (20–79%) [2]. The use of foot orthoses is one of the most used strategies in the treatment of overuse running injuries [3,4]. Among the injured running population, the use of orthoses has been especially effective to runners with an excessive pronation or a length discrepancy [5], or pathologies such as patellofemoral pain [6] or chronic Achilles tendon injury [7]. Despite the unclear evidence of the effect of foot orthoses in healthy recreational runners, its use is very usual as a mechanism of injury prevention and performance improvement [8–10]. In addition, runners perceive that footwear, where foot orthoses could be included, is one of the main factors associated with injury risk [11].

It has been observed that foot orthoses are able to reduce impact forces associated with running [12,13], to improve plantar pressure distribution [14,15], comfort perception [14,16] or to lead to kinematic changes [14,17,18]. However, the effect of foot orthoses during running has usually been studied through running trials, which may not be representative enough of the running load experienced by runners during their training sessions and competitions. In this sense, it would be interesting to investigate the effect of foot orthoses in a prolonged race, which should offer a more real vision of the recreational runners’ usual practice [19]. Two previous studies of our research group [20,21] observed that foot orthoses have an effect on spatio-temporal, shock and plantar loading parameters after a prolonged run. The modification of those parameters could be associated with changes in kinematic parameters such as knee flexion and foot eversion [7,22], which are related with injury incidence [23], and justifies its investigation.

In this line, athletes may undergo kinematic modifications during a prolonged run in order to protect themselves from injuries, to maintain their performance level or as a result of fatigue [24]. In scientific literature, the most commonly kinematic adjustments observed are the increase in contact time, stride length, foot eversion and knee flexion [25–27]. By contrast, it has been speculated that foot orthoses could modify spatio-temporal kinematics [18] and angular kinematics during running due to the pronation motion control that they offer [7,8]. The type of foot orthosis could also have an influence in kinematic adjustments. Better results are commonly expected with custom-made foot orthoses than with prefabricated foot orthoses, due to its individual adaptation [28,29]. However, some authors have found a decrease in foot eversion with custom-made foot orthoses [9,14,30], while other studies have observed the same effect with prefabricated ones [17,31]. According to one of the last paradigms postulated by Nigg et al. [23,32], the use of footwear (or foot orthoses, in this case) should allow healthy runners to maintain their preferred movement path, so caution should be taken with kinematic alterations, since they will not always be positive. In this sense, there is a lack of information regarding the kinematic effects of foot orthoses during a prolonged run.

Therefore, the aim of the present study was to analyse the effect of different foot orthoses (custom-made, prefabricated and a control condition) on spatio-temporal and angular (knee flexion and foot eversion) kinematic parameters, as well as their behaviour during an intense prolonged run.

Methods

Participants

Twenty-four recreational runners: 18 males and 6 females (mean (standard deviation): age 34 (5) years; body mass 71.4 (12.5) kg; height 1.75 (0.08) m; running training distance 37.5 (12.8) km∕week) participated voluntarily in the present study. Inclusion criteria were: I) no history of lower extremity injuries within the last six months, II) no previous use of foot orthoses, and III) a training routine of at least 15 km/week. All runners signed the written informed consent before participation. The study procedures complied with the requirements established in the Declaration of Helsinki, and the study was approved by the University Ethics Committee (Comité Ético de Investigación en Humanos de la Comisión de Ética en Investigación Experimental de la Universitat de València, approval number H1427706182089).

Foot orthosis conditions and customisation

Participants used three different foot orthosis conditions (Fig 1), on different days, and their order was previously randomised: 1) original insole of the shoe as a control condition; 2) prefabricated foot orthoses, chosen only according to athletes’ foot size (Tecnoped Run, Herbitas, Valencia, Spain); and 3) custom-made foot orthoses built from a three-dimensional representation of the athlete’s feet (OPCT Run, Sidas S.L., Barcelona, Spain). For the customisation of the custom-made foot orthoses, participants stood on a Printlab2 platform (Podiatech, Sidas Technologies, Voiron, France), composed of a pair of silicon vacuum bags that allowed the recreation of the plantar print. Based on the foot print and while the subastragaline joint was in a neutral position, a plaster mould was created, and through a thermo-welding process (Podiatech, Sidas Technologies, Voiron, France) the three dimensional foot orthoses customised to the participant’s foot were built.

Fig 1. Properties of the foot orthoses.

Fig 1

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Protocol

The study consisted of four tests on different days separated by a week: an initial field test and three laboratory tests, each one with a foot orthosis condition (Fig 2). The aim of the field test was to determine the individual maximal aerobic speed (MAS) in order to calculate the individual running speeds for the laboratory tests. In this first session, participants were asked to run as maximum distance as possible during 5-min on a 400-m track and their individual MAS was determined from the total distance/time [33]. The three laboratory tests consisted of running 20 min on a treadmill (Excite Run 900, TechnoGymSpA, Gambettola, Italy) at 80% of their individual MAS, with a slope of 1%, to simulate the physiological load of an outdoor run [34]. Prior to these running tests, the athletes ran for 10 min at 60% of their MAS as a warm up exercise. Before each laboratory test, the runners trained for a week progressively with the foot orthosis assigned as an adaptation period [20]. In this adaptation period, participants were asked to wear the foot orthoses during the whole day for the first two days and, during the training sessions of these days, only in the warm-up and the cool down. From the third day onwards, if they did not experience discomfort, they had to wear the foot orthoses during their entire training session [35]. In addition, the participants wore their own running footwear in the three tests and in their adaptation periods in order to introduce no further changes in their running customary condition [36]. Perceived exertion was asked by means of the 20-point Borg scale [37], and heart rate was measured (Polar Electro Inc, Woodbury, USA), both at the beginning and the end of the test in order to control the test’s intensity.

Fig 2. Study design.

Fig 2

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Data collection and analysis

During each laboratory test, spatio-temporal kinematic parameters were collected with an optical measurement photoelectric cell system (OptoGait, Microgate, Bolzano, Italy) consisting of two bars located on the treadmill [38]. Contact time, flight time, stride length and stride rate were recorded for each foot every 5 min for 15 s during the main part of the running tests (20 min at 80% MAS). Data were extracted at 1000 Hz, and calculated with the OptoGait software program (Version 1.9.9.0, Microgate, Bolzano, Italy).

In addition, foot eversion and right knee flexion were analysed by two high-speed cameras (MotionScope®, Redlake, MASD Inc., San Diego, USA) sampling at 125 Hz. One camera was placed 1.5 m perpendicular to the motion plane and 0.5 m high to measure the frontal plane, and the other camera was placed 1.5 m perpendicular to the right motion plane and 1 m high to measure the sagittal plane. Angular kinematic data were recorded simultaneously with the Optogait, every 5 min for 5 s during the 20 min run. Both cameras were synchronised with the camera software (Redlake MASD MotionScope®, San Diego, USA), and data were analysed using a motion analysis software (Kinescan/IBV System, Valencia, Spain) [39]. Prior to each measurement, optical distortion of the camera lens and calibration of the space were performed using a square object of known dimensions in which four space references were attached. Calibration was performed via bidimensional (2D) direct linear transformation using the motion analysis software. The spline smoothing method was used automatically in the motion analysis software [40].

For the kinematic analysis of the right knee flexion a 2D model of 3 reflective spherical markers (diameter: 16 mm) was used as in previous studies [41]. Markers were placed in the right leg: 1) on the greater trochanter of the femur, 2) on the lateral femoral epicondyle of the knee, and 3) on the lateral malleolus of the ankle. Knee flexion was calculated by the projected α angle between the two segments (thigh and leg) defined by the kinematic model [41] (Fig 3). In addition, foot eversion of both feet was analysed using Clarke et al.’s 2D model of four markers [42,43] placed: 1) on the gastrocnemius (in the axial line of the leg, under the gastrocnemius bifurcation), 2) on the Achilles tendon (at the height of the malleolus), 3) on the upper part of the calcaneus, and 4) on the lower part of the calcaneus. The projected β angle between the two segments (calcaneus and leg) defined by the kinematic model [12,43] was used to calculate foot eversion (Fig 3). To normalise the values, knee flexion and foot eversion angles were calculated from a static standing trial wearing the assigned foot orthoses condition, considered as 0° [41,43].

Fig 3.

Fig 3

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Placement of markers and kinematic 2D models used to measure α angle of knee flexion (left) and β angle of foot eversion (right) during running.

The variables of interest were: knee flexion at contact time, maximum knee flexion during stance phase, knee flexion at toe-off, maximum knee flexion during swing phase, foot eversion at contact time, and maximum foot eversion during the stance phase. These variables were calculated from the average of 5 steps [7,41]. Angles during toe-off and swing phase were measured due to the anti-shock and propulsive properties suggested by the foot orthoses manufacturer.

Statistical analysis

For the statistical analysis, data were analysed using a statistical package (SPSS 20.0, IBM, Armonk, USA). After confirming the normality of the sample in all the variables by the Shapiro Wilks test (P > 0.05), and verifying the sphericity by the Mauchly Sphericity test, the descriptive statistics were extracted. Data were reported as mean (standard deviation (SD)). Then, 2-way repeated-measures ANOVAs were performed for each dependent variables of the study. Two factors were used as intra-subject factors: foot orthosis condition, with three levels (control, prefabricated and custom-made) and time points with 2 levels in rate of perceived exertion and heart rate (minute 1 and minute 19) and 5 levels in kinematic parameters (minutes 1, 5, 10, 15 and 20). For the significant ANOVA models (P < 0.05), the Bonferroni correction post-hoc test was carried out. For the pair significant differences (P < 0.05), the Cohen’s effect size (ES) was computed and classified as small (ES 0.2–0.5), moderate (ES 0.5–0.8) or large (ES > 0.8) [44]. Significance level was stablished at α = 0.05.

Results

Rate of perceived exertion and heart rate values are presented in Table 1. For rate of perceived exertion and heart rate, no significant main effect of condition (P > 0.22) or time-by-condition interaction effect (P > 0.21) was found. However, there was a main effect of time (P < 0.001; ES > 1.0). These results indicate an increase of rate perceived exertion and heart rate at the end of the run regardless of the foot orthosis condition.

Table 1. Perceived exertion rate and heart rate differences between time points (Begin vs. End) in each foot orthosis condition.

Control Prefabricated Custom-made
Mean (SD) Mean (SD) Mean (SD)
Begin End Begin End Begin End
Perceived exertion rate (points) 12.7 (1.2) 14.3 (1.7) 12.8 (1.1) 14.7 (1.7) 13.0 (1.5) 15.0 (2.0)
Heart rate (bpm) 162.8 (9.3) 171.9 (9.1) 158.6 (10.5) 170.3 (10.8) 160.1 (11.2) 172.3 (12.0)
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No differences were observed between feet in spatio-temporal and foot eversion parameters (P > 0.05). Therefore, foot dominance factor was not considered in the repeated measures ANOVA and the mean of both feet is presented for these variables.

Tables 2–4 show the behaviour of spatio-temporal, knee flexion and foot eversion parameters, respectively, during the running test on each foot orthosis condition. There was no significant main effect of condition (P > 0.36) and no significant effect in the interaction time-by-condition (P > 0.18) in any of the kinematic variables (spatio-temporal, knee flexion and foot eversion parameters) except for a main effect of time only in contact time and maximum eversion during the stance phase (P < 0.01). In contact time, this result implies higher values in minute 10 vs minute 1 (P = 0.02; ES = 0.2) and in minute 20 vs minute 1 (P = 0.02; ES = 0.2), both of them with a small effect size. Moreover, in maximum eversion during the stance phase, this result implies higher values at each time point studied with respect to minute 1 (min 1 vs min 5 (P < 0.001; ES = 0.2); vs min 10 (P < 0.001; ES = 0.2); vs min 15 (P = 0.001 ES = 0.2); vs min 20 (P < 0.001 ES = 0.3), showing in all cases a small effect size. In all the other variables, no significant main effect of time was found (P > 0.44).

Table 2. Spatio-temporal parameters during the 5 time points of the running test with the 3 foot orthosis conditions.

Variable Minute Control Prefabricated Custom-made
Mean (SD) Mean (SD) Mean (SD)
Stride Length (m) 1 2.45 (0.31) 2.48 (0.33) 2.47 (0.32)
5 2.45 (0.32) 2.48 (0.33) 2.48 (0.34)
10 2.46 (0.32) 2.48 (0.32) 2.47 (0.33)
15 2.46 (0.31) 2.48 (0.32) 2.48 (0.33)
20 2.47 (0.32) 2.47 (0.30) 2.44 (0.40)
Stride Rate (Hz) 1 1.43 (0.06) 1.42 (0.07) 1.43 (0.07)
5 1.43 (0.06) 1.42 (0.07) 1.42 (0.07)
10 1.42 (0.07) 1.42 (0.07) 1.42 (0.07)
15 1.42 (0.06) 1.42 (0.07) 1.41 (0.07)
20 1.41 (0.06) 1.43 (0.07) 1.41 (0.07)
Contact Time (s) 1 0.268 (0.023) 0.268 (0.024) 0.269 (0.024)
5 0.271 (0.023) 0.271 (0.024) 0.271 (0.025)
10 0.272 (0.021) 0.273 (0.025) 0.273 (0.021)
15 0.271 (0.021) 0.275 (0.024) 0.273 (0.022)
20 0.273 (0.022) 0.273 (0.024) 0.275 (0.025)
Flight Time (s) 1 0.083 (0.026) 0.085 (0.029) 0.082 (0.026)
5 0.081 (0.026) 0.081 (0.028) 0.081 (0.030)
10 0.080 (0.025) 0.080 (0.029) 0.080 (0.026)
15 0.083 (0.023) 0.078 (0.028) 0.081 (0.026)
20 0.080 (0.027) 0.079 (0.026) 0.080 (0.030)
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No differences were observed in the interaction between foot orthosis condition and time point (P > 0.05).

Table 4. Foot eversion parameters during the 5 time points of the running test with the 3 foot orthosis conditions.

Variable Minute Control Prefabricated Custom-made
Mean (SD) Mean (SD) Mean (SD)
Foot eversion at contact time (°) 1 -5.97 (5.79) -6.50 (6.41) -6.10 (7.00)
5 -5.92 (6.26) -6.53 (6.85) -6.25 (7.39)
10 -5.71 (6.14) -6.27 (7.10) -6.36 (7.13)
15 -6.22 (6.45) -6.42 (6.99) -6.73 (7.68)
20 -6.01 (6.09) -6.18 (7.15) -6.61 (6.98)
Maximum foot eversion during stance phase (°) 1 10.98 (4.16) 10.30 (3.85) 10.66 (4.23)
5 11.66 (4.00) 11.21 (4.18) 11.43 (4.38)
10 11.56 (3.76) 11.53 (4.99) 11.64 (4.70)
15 11.91 (3.88) 11.30 (4.13) 11.59 (4.65)
20 11.87 (4.09) 11.76 (4.36) 11.70 (4.92)
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No differences were observed in the interaction between foot orthosis condition and time point (P > 0.05).

Table 3. Knee flexion parameters during the 5 time points of the running test with the 3 foot orthosis conditions.

Variable Minute Control Prefabricated Custom-made
Mean (SD) Mean (SD) Mean (SD)
Knee flexion at contact time (°) 1 12.17 (4.46) 11.45 (5.69) 12.19 (4.44)
5 12.11 (4.67) 11.89 (6.01) 11.89 (4.08)
10 12.30 (5.14) 11.73 (6.37) 12.28 (4.23)
15 12.12 (4.63) 11.53 (5.76) 12.73 (5.05)
20 11.86 (4.74) 11.58 (5.99) 12.23 (5.19)
Maximum knee flexion during stance phase (°) 1 39.31 (4.70) 38.53 (5.77) 39.01 (4.37)
5 39.12 (4.91) 38.73 (5.69) 38.99 (4.13)
10 38.65 (4.56) 38.98 (5.40) 39.45 (4.45)
15 38.69 (4.51) 38.72 (6.32) 39.70 (4.72)
20 38.02 (5.04) 38.90 (5.40) 39.05 (5.13)
Knee flexion at toe-off (°) 1 10.78 (4.77) 11.19 (5.61) 11.03 (5.65)
5 11.01 (4.90) 10.97 (5.84) 10.27 (5.52)
10 9.82 (5.05) 10.74 (5.77) 10.69 (5.69)
15 10.22 (5.18) 10.95 (6.05) 10.97 (6.23)
20 10.04 (5.00) 11.35 (6.14) 10.70 (5.90)
Maximum knee flexion during swing phase (°) 1 87.74 (10.52) 88.49 (10.94) 86.92 (10.66)
5 88.59 (10.24) 87.40 (9.92) 88.18 (10.95)
10 87.34 (10.39) 88.23 (9.71) 87.54 (10.67)
15 88.26 (10.63) 88.29 (9.94) 87.63 (10.31)
20 88.46 (11.18) 87.73 (9.50) 87.35 (11.23)
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No differences were observed in the interaction between foot orthosis condition and time point (P > 0.05).

Percent changes of the biomechanical variables for each participant as well as the number of participants that showed a biomechanically relevant change (±10%) [36] regarding the control condition are provided in the Supplementary File.

Discussion

The purpose of this study was to analyse the effects of custom-made and prefabricated foot orthoses on spatio-temporal and angular kinematic parameters during an intense prolonged run. The main result of the study was that there was not a significant main effect of foot orthosis or an interaction between foot orthosis and time on the spatio-temporal and angular kinematic variables assessed during running.

It is well known that during a high intensity run, and consequently, with the development of it, some kinematic alterations previously associated with injury and performance optimisation can occur [24,27]. In this line of thought, it has been suggested that the use of foot orthoses may be a great strategy to counteract those changes, for example through greater control of foot pronation [17,45]. In this sense, in the present work the effect on spatio-temporal and angular kinematic parameters of different foot orthoses were analysed in different time points of an intense prolonged run of 20 minutes of duration, in order to know the behaviour of those parameters throughout this time in a more ecological protocol [19]. Currently, there is little information on the effectiveness of foot orthoses during an intense run. Only the studies of Lucas-Cuevas et al. [20,21] analysed some spatio-temporal parameters in a continuous running protocol, with three different foot orthosis conditions (similar to those used in the present work), but only at the beginning and at the end of the run, without looking at their behaviour throughout the run.

In the present study, and according to the results of these two investigations [20,21], no significant differences in several spatio-temporal parameters under three different conditions of foot orthoses as well as in the interaction between foot orthosis and running time were observed. A previous study has shown that runners are able to achieve a lower metabolic expenditure by adjusting these parameters in an unconscious and individual way [46]. Therefore, these results could explain that the intervention with foot orthoses does not involve a greater energy expenditure, because it is not necessary to modify these parameters with respect to the control condition during an intense prolonged run of 20 minutes. In addition, running with foot orthoses could be affecting other variables such as ground reaction forces, neuromuscular activation or comfort. Previous studies have observed that the use of foot orthoses seems to reduce impacts and to improve the comfort perception of runners in relation to not wearing them [20,21,30]. In this line of thought, foot orthoses could be prescribed seeking these benefits without compromising the athlete’s running technique during an intense prolonged run. Therefore, future studies should address the effect of foot orthoses from a holistic perspective that include the combined assessment of kinematics, comfort, neuromuscular activation, and ground reaction forces.

In the present study, none of the variables of knee flexion was altered throughout the run when using foot orthoses (custom-made and prefabricated) in comparison with the control condition. These results are in agreement with previous studies performed in trials [9,13,45]. This lack of modifications found in knee flexion could be attributed to the idea that the running movement is pre-programmed, and in healthy runners the running pattern normally used could already be the ideal one, without needing an alteration of the same [23,32]. So, its change would lead to an increase in metabolic expenditure [23,32]. Therefore, as the athletes in this study were injury-free, they could have adapted the use of the foot orthoses to their pre-established movement pattern during the training period with them.

In addition, according to Nigg et al. [23,32], an intervention with foot orthoses would be beneficial if it allows to maintain the ideal and preferred movement path. In this line, Lucas-Cuevas et al. [20] used the same foot orthoses and a similar sample population as in the present investigation, and these authors observed lower acceleration rates with the custom-made orthoses compared to the prefabricated ones. This reduction in the acceleration rate, along with the lack of modifications in the knee flexion observed by the present study, could suggest a higher level of protection by the custom-made foot orthoses, as their use would avoid unnecessary alterations in the movement pattern and the kinematic chain to reduce the impacts, which could be harmful [23].

With respect to foot eversion, a large number of studies have analysed the effect of foot orthoses aiming to control pronation, but only in trials or brief run protocols and ultimately finding different results. In the present study, the use of foot orthoses did not produce any change in the maximum foot eversion during stance phase or in the foot eversion at contact time in any of the analysed time points, in comparison with the control condition. Similarly, previous studies with healthy runners also found no changes in foot eversion [36,47]. On the contrary, in studies looking into a running population with pathologies, such as patellofemoral syndrome, anterior knee pain and chronic Achilles tendon injury, changes in foot eversion were observed as a result of using foot orthoses [7,45,48]. These findings suggest that the type of population may influence the variability of results. Therefore, the lack of modifications in these parameters could be explained, as mentioned in the knee flexion, by the fact of having studied athletes without injuries, who would not need to use a rearfoot motion control strategy and who were able to maintain their ideal running pattern during the 20 minutes of run. In addition, while previous authors found decreases in foot eversion with both custom-made [9,14,30], and prefabricated foot orthoses [17,31], no differences were found in this study between the two types of foot orthoses. Therefore, other hypotheses that could justify these results are the specific characteristics of the foot orthoses, which were not specifically manufactured to limit the movement of the ankle [12]; and the protocol used to measure these parameters [8,49].

Regarding the running protocol used in this study, participants reported perceived exertion values between 13 and 15 points as well as heart rate values between 158 and 172 bpm, at the beginning and at the end of the tests, respectively. These values correspond to a somewhat hard/hard intensity, and show that athletes performed the 20 min tests at the anaerobic threshold level [50]. In a previous study [51], no differences were observed between the three foot orthosis conditions in any of the two parameters, neither at the beginning nor at the end of the running protocol. In the present study, however, there was a significant increase in perceived exertion and heart rate at the end of the running protocol in the three foot orthosis conditions, which shows that there was a progression in the intensity of the effort throughout the running protocol.

Despite this fact, in this study no kinematic changes were observed at the different time points of the running test. There was only a main effect of time in contact time and maximum eversion during the stance phase, regardless of foot orthosis condition, which implied certain increases in these variables as the athletes were completing the running tests, with small effect sizes. This lack of changes throughout time could be due to an insufficient level of fatigue. In this sense, the athletes of this study, despite having worked at the anaerobic threshold, may have not reach a sufficient level of muscular fatigue to produce changes in the movement pattern [20]. As a result, it is possible that the modifications or compensatory adaptations could have taken place at the neuromuscular level, without showing changes in the kinematic pattern of movement. Therefore, the intensity of the running tests, which was not hard or long enough to produce movement pattern alterations throughout the run, could be suggested as a possible limitation of the study. Future studies should assess the effect of custom-made and prefabricated foot orthoses on kinematic parameters after longer or more intense protocols.

The main limitation of this study was the use of 2D video to analyse running kinematics instead of using the “gold standard” 3D video analysis. However, it has been stated that 2D video analysis is accurate enough to assess frontal plane variables of treadmill running [52]. Likewise, the study of a single plane in both the knee and the ankle could also be considered a limitation, since other planes could have shown kinematic modifications, as in the knee abduction and adduction movements [49,53]. Another limitation to take into account was the small number of women that took part in the study. A larger sample of female runners would have enabled the analysis of movement patterns by gender, as it is known that women have structural differences which can lead to differences in running mechanics [54] and to a different influence of foot orthoses.

From this point of view, although no differences have been found between the three foot orthosis conditions studied from a grouped perspective, in the studies of foot orthosis and footwear it is common to find a large variability of response among participants, which is masked by the overall results [36]. In the present study, as presented in the Supplementary File, the spatio-temporal parameters have not been affected by inter-subject variability, since most participants have not experienced a relevant change. However, in the angular parameters, the effects of different directions and magnitudes have been observed both among participants as well as within a single individual. In the future, it would be interesting to study if these different responses to a foot orthosis implementation could be grouped by some participant characteristics, such as the gender or the type of foot.

In addition, in future studies it would be interesting to investigate the effect of this foot orthosis intervention in a pathological population or with pain, in order to know if the use of foot orthosis may have some effect in such pathology, with a consequent kinematic alteration. Furthermore, it would also be interesting to analyse the patterns of movement by gender, with an equivalent sample, by the aforementioned differences between men and women. Finally, the study of the long-term effects of a similar intervention of foot orthoses could be of interest in order to understand the influence over time of using orthoses on running mechanics, even with the creation of two groups: one control and another using specific foot orthoses.

Conclusions

The findings of this study show that the use of custom-made and prefabricated foot orthoses during an intense prolonged run does not produce changes in spatio-temporal and angular (knee flexion and foot eversion) kinematic parameters, compared to a control condition. This lack of modifications in the running mechanics of the athletes may suggest that a healthy runner population is able to maintain their ideal movement pattern throughout a 20 minute prolonged run, regardless of the type of foot orthosis used.

Supporting information

S1 Fig. Percent changes relative to control foot orthosis condition for spatio-temporal parameters regardless the time points of the running test.

(JPG)

Click here for additional data file. (626.1KB, jpg)
S2 Fig. Percent changes relative to control foot orthosis condition for knee flexion parameters regardless the time points of the running test.

(JPG)

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S3 Fig. Percent changes relative to control foot orthosis condition for foot eversion parameters regardless the time points of the running test.

(JPG)

Click here for additional data file. (287.4KB, jpg)
S1 Table. Number of participants experiencing biomechanically relevant reductions (≥10% Reduction), biomechanically relevant increases (≥10% increase), and no change (change between -9.9% and +9.9%) for each variable, regardless the time points of the running test, when wearing prefabricated or custom-made foot orthoses compared to control condition.

(DOCX)

Click here for additional data file. (15.4KB, docx)

Acknowledgments

We thank all the participants for their voluntary participation in this study.

Data Availability

Data are available from DOI: 10.17632/ftnk8m3hdd.1 (http://dx.doi.org/10.17632/ftnk8m3hdd.1)

Funding Statement

The work of IJP was supported by the Spanish Government (Ministerio de Ciencia, Innovación y Universidades, Grant FPU14//05626). In addition, the research project was supported by the Spanish Government (Ministerio de Economía y Competitividad, Subdirección General de Proyectos de Investigación. Convocatoria Proyectos I+D “Excelencia”, Subprograma de Generación de Conocimiento, 2013 (project DEP2013-48420-P)). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

References

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Decision Letter 0

Alena Grabowski

9 Dec 2019

PONE-D-19-28910

Effect of custom-made and prefabricated foot orthoses on kinematic parameters during an intense continuous run

PLOS ONE

Dear Ms. Jimenez-Perez,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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Reviewer #2: Yes

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Reviewer #1: Overall/General comments and primary concerns:

Given that the purpose of the study is to investigate the effects of orthoses during a prolonged run, I recommend that the authors focus the introduction to describe what kinematic changes do occur over the course of a prolonged run and what benefits orthoses may provide. The current focus of the introduction is to describe the more general research surrounding orthoses so the inclusion of the prolonged running seems to me more of an afterthought than a focus.

The introduction should also describe and explain why healthy runners are an appropriate population to study for this investigation given that orthoses were originally designed to help patient populations. I suggest that the authors should discuss runner’s use of these products to prevent injury. The survey study in JOSPT on runner’s beliefs about injury may be helpful in this regard. Please also provide a rationale for examining knee flexion and be more explicit about why foot eversion was studied (I imagine that the reason is that orthoses are intended to modify eversion primarily, but whatever the reason should be stated).

It did not appear that the authors examined the individual subject data. Footwear and foot orthoses research is notorious for finding insignificant differences, not because the conditions have no effect but because the inter-individual variation in the response to the conditions is so large.

The discussion was a bit outside of the scope of the present study in some areas (for example, with respect to energy expenditure and what affect that may have on the results. The present study only examined HR and RPE, neither of which were between orthosis conditions). Any discussion regarding energy expenditure or running economy should be brief, to the point, and within the scope of the present study (i.e. one paragraph of no more than 10-12 lines in length). The scope of the paragraph discussing the knee flexion results (line 299-319) is a good example of the scope that should be used to explain the other variables and length should not exceed that of this example section, given the results and the overall scope of the study.

Similar to the introduction, the discussion section seems to focus on the differences between conditions in the primary outcome variables (knee angle, eversion angle, and spatio-temporal parameters), rather than the effects of the orthoses on the prolonged run. I understand that it is difficult to explain the effects that the orthoses had on the prolonged run given that there were no significant differences observed. However, the purpose of this suggestion is make sure the discussion surrounding the prolonged run aspect of this study is not seen as an afterthought; it should be the focus of both the intro and discussion because it is the primary difference compared with previous studies.

Abstract

1. Line 21-23: I recommend revising this section of the abstract to reflect better why healthy runners would chose to wear foot orthoses or shoe inserts and thus why they are a good sample to study rather than a patient population.

2. Line 36-38: I recommend changing the last sentence of the conclusion to be something that can be said about the present study. Additional work can always be done but a more impactful conclusion would reflect what can be learned by the present study. As discussed above, commenting about inter-individual differences may be a good topic to replace this last sentence (see further comment below about the inter-individual differences).

Introduction

3. Line 45: Please be specific here as to not unintentionally spread speculation. The referenced study seems to be about Achilles tendon injuries alone. Also, please confirm that the findings of this study were indeed that the orthoses prevented injury, which is the statement in the text of the present study. Citations should reference the findings, not the speculation or theories proposed by others.

4. Line 60: “…no clear evidence…of the effect of foot orthoses on running kinematics” is not clear because the authors described some kinematic variables earlier in this paragraph. Please be more specific as to what is still unknown. Also in this paragraph, the ‘preferred movement path’ is discussed as a follow-up to describing that there is not a lot of evidence regarding spatio-temporal variables. Although both portions of the sentence are true individually, they should not be together because the preferred movement path is less a consideration for spatio-temporal characteristics, and more about joint and segment kinematics.

Methods

5. The authors described that they tested if the variables were normally distributed but did not describe the results of these tests in the statistical analysis section of the methods or in the results. Please describe which variables, if any, were non-normally distributed and what was done (if anything) to adjust for non-normal data.

Results

6. Line 215-216: The end line 216 which is part of the sentence, “there was no significant main effect…in any of the kinematic variables; however, there was a main effect for…” should be changed to “…in any of the kinematic variables except for a main effect for…”. More simply stated, please change “however” to “except for”

7. As described in the general/overall comments, it may be beneficial to examine the inter-individual differences.

Discussion

8. Line 250: The findings of the referenced study were not “harmful kinematic alterations.” We do not have enough longitudinal evidence to imply that any cross-sectional study is harmful.

9. Line 258: These are the only studies that looked at spatio-temportal parameters with respect to what? Orthoses? These are far from the only prolonged running studies out there. This sentence should be more specific.

10. Line 275: Need to explain how the methods of referenced study (Wilkinson et al) are similar and different than the present study so the reader can have more context to understand why the results between the two studies are being compared and understand the potential explanation for the differences. Start the paragraph explaining this information rather than bring it in later (i.e. line 279-283).

Figures and tables

11. There is a typo with the spelling of ‘length’ in Figure 4

12. It is my personal preference to have the full variable name used as figure titles instead of the abbreviation. That way, I don’t have to remember or look back at what something is, I know it the instant that I look at it.

Reviewer #2: Overall, the manuscript is well-written, with a few areas where the use of English grammar is not quite up to expectations. The authors do well to provide background review of the literature and justification for the study. It seems the gap that the authors hope to fill is the effect of custom orthoses over time-course of an intense continuous run. However, the findings of the study indicate that there was no statistical difference to report. A null finding is not considered a negative thing, but it does substantially reduce the enthusiasm for this study. Additionally, while the authors have provided a thorough treatment of the data and kept their conclusions within the scope of the statistical results, they do tend to overstate potential application of this work in the Conclusion statement. I'm not sure that enough evidence was presented to say that impact reduction with orthoses can be a benefit "without interfering in the running technique or running economy".

There are a large number of figures, which are unfortunately not very informative. Figures 1-3 are generally helpful to explain the methods, but the information in Figures 4-6 could easily be placed in a table, or in supplementary material, as they really do not show anything more than what the authors have stated in the text.

The discussion section is excessively long, with too much revisitation of the previous work. Rather than re-reviewing all of the literature here, the manuscript would be improved with a critical evaluation of the points in the literature which may help explain why the current study resulted in null findings.

**********

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Reviewer #2: No

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PLoS One. 2020 Mar 26;15(3):e0230877. doi: 10.1371/journal.pone.0230877.r002

Author response to Decision Letter 0

14 Jan 2020

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

In the revised manuscript, you need to address all of the comments posed by the reviewers. Specifically, please provide more focused introduction and discussion sections, discuss individual variation in relation to the present study, relate the paper to the effects on a prolonged run, and justify the subject population.

Dear editor, we are grateful for the opportunity to revise our paper. All the comments sent by the reviewers were carefully addressed. All the changes in the edited manuscript are highlighted with red text in the revised submission. We look forward to hearing your editorial decision.

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Please amend your current ethics statement to include the full name of the ethics committee/institutional review board(s) that approved your specific study.

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Reply: We would like to thank the editor for this comment. We have include the full name of the ethics committee in Methods section of the manuscript, and to the “Ethics Statement” field of the submission form, as follow (Page 5, Lines 96-100):

“The study procedures complied with the requirements established in the Declaration of Helsinki, and the study was approved by the University Ethics Committee (Comité Ético de Investigación en Humanos de la Comisión de Ética en Investigación Experimental de la Universitat de València, approval number H1427706182089).”

3. We note that your study is closely related to the following publication, on which you are an author:

https://doi.org/10.1371/journal.pone.0173179

Although you have cited the above study in the discussion section of your article, we feel that the scientific rationale of the current study and the contribution that it makes to the field should be better justified. Therefore, please cite and discuss the above study in the introduction section of your manuscript, clarifying how the present work is related to the previously published paper.

Please note that our second publication criterion states that "If a submitted study replicates or is very similar to previous work, authors must provide a sound scientific rationale for the submitted work and clearly reference and discuss the existing literature. Submissions that replicate or are derivative of existing work will likely be rejected if authors do not provide adequate justification." http://www.plosone.org/static/publication.action#results.

Reply: We would like to thank the editor for this comment. We have cited and discussed this publication in the introduction section, to clarify that it is a previous study of our research group, as suggested (Page 3, Lines 60-65):

“Two previous studies of our research group [20,21] observed that foot orthoses have an effect on spatio-temporal, shock and plantar loading parameters after a prolonged run. The modification of those parameters could be associated with changes in kinematic parameters such as knee flexion and foot eversion [7,22], that are related with the injury incidence [23], which justifies its investigation.”

4. We note that you have stated that you will provide repository information for your data at acceptance. Should your manuscript be accepted for publication, we will hold it until you provide the relevant accession numbers or DOIs necessary to access your data. If you wish to make changes to your Data Availability statement, please describe these changes in your cover letter and we will update your Data Availability statement to reflect the information you provide.

Reply: Yes, it is right, after acceptance, we will provide the DOI of the repository information of our data.

Reviewers' comments:

Reviewer #1: Overall/General comments and primary concerns:

Given that the purpose of the study is to investigate the effects of orthoses during a prolonged run, I recommend that the authors focus the introduction to describe what kinematic changes do occur over the course of a prolonged run and what benefits orthoses may provide. The current focus of the introduction is to describe the more general research surrounding orthoses so the inclusion of the prolonged running seems to me more of an afterthought than a focus.

Reply: We would like to thank the reviewer for this recommendation. We have rearranged the introduction to focus it from the beginning on the effect of the prolonged run. Moreover, we have put together the description of the kinematic changes of a prolonged run and the benefits that foot orthoses can provide, to give a clearer vision of the study purpose.

In addition, throughout the manuscript the term “continuous run” has been changed by “prolonged run”.

The introduction should also describe and explain why healthy runners are an appropriate population to study for this investigation given that orthoses were originally designed to help patient populations. I suggest that the authors should discuss runner’s use of these products to prevent injury. The survey study in JOSPT on runner’s beliefs about injury may be helpful in this regard. Please also provide a rationale for examining knee flexion and be more explicit about why foot eversion was studied (I imagine that the reason is that orthoses are intended to modify eversion primarily, but whatever the reason should be stated).

Reply: We would like to thank the reviewer for this comment. We have modified the introduction following reviewer recommendation as follow (Page 3, Lines 46-53):

“The use of foot orthoses is one of the most used strategies in the treatment of overuse running injuries [3,4], being the most benefited runners those with an excessive pronation or a length discrepancy [5], or pathologies such as patellofemoral pain [6] or chronic Achilles tendon injury [7]. Despite the unclear evidence of the effect of foot orthoses in healthy recreational runners, its use is very usual in this population as a mechanism of injury prevention and performance improvement [8–10]. In addition, runners perceived that footwear, in which foot orthoses could be included, is one of the main factors associated with injury risk [11].”

On the other hand, we have added information on knee flexion and foot eversion, as requested (Page 3, Lines 62-65):

“The modification of those parameters could be associated with changes in kinematic parameters such as knee flexion and foot eversion [7,22], that are related with the injury incidence [23], which justifies its investigation.”

And (Page 4, Lines 70-73):

“By contrast, it has been speculated that foot orthoses could modify spatio-temporal kinematics [18] and angular kinematics during running, due to its usual aim of control of pronation [7,8].”

It did not appear that the authors examined the individual subject data. Footwear and foot orthoses research is notorious for finding insignificant differences, not because the conditions have no effect but because the inter-individual variation in the response to the conditions is so large.

Reply: We are totally agree with this comment about the inter-individual variation effects on the results. For this reason, we have carried out repeated-measures ANOVAs that compare each subject with himself in the different conditions, since each participant went through the 3 types of foot orthoses and the 5 time points of measurement. This type of analysis is taking into account the intra-individual variations as suggested by the reviewer.

The discussion was a bit outside of the scope of the present study in some areas (for example, with respect to energy expenditure and what affect that may have on the results. The present study only examined HR and RPE, neither of which were between orthosis conditions). Any discussion regarding energy expenditure or running economy should be brief, to the point, and within the scope of the present study (i.e. one paragraph of no more than 10-12 lines in length). The scope of the paragraph discussing the knee flexion results (line 299-319) is a good example of the scope that should be used to explain the other variables and length should not exceed that of this example section, given the results and the overall scope of the study.

Reply: We are grateful to the reviewer for this comment. We agree with the reviewer that some of our discussion was outside of the scope of our study. Therefore, we had reduced the information of the discussion related with energy expenditure or running economy.

Similar to the introduction, the discussion section seems to focus on the differences between conditions in the primary outcome variables (knee angle, eversion angle, and spatio-temporal parameters), rather than the effects of the orthoses on the prolonged run. I understand that it is difficult to explain the effects that the orthoses had on the prolonged run given that there were no significant differences observed. However, the purpose of this suggestion is make sure the discussion surrounding the prolonged run aspect of this study is not seen as an afterthought; it should be the focus of both the intro and discussion because it is the primary difference compared with previous studies.

Reply: We would like to thank the reviewer for this comment. We modified our discussion increasing its focus in the prolonged run. We maintained the structure of discussing the primary outcome variables, because we think that the focus of prolonged run should be included in all the paragraphs of the discussion, and this structure is an easy way for the reader to follow the discussion of our results.

Abstract

1. Line 21-23: I recommend revising this section of the abstract to reflect better why healthy runners would chose to wear foot orthoses or shoe inserts and thus why they are a good sample to study rather than a patient population.

Reply: We would like to thank to the reviewer for this comment. This section has been modified as follows (Page 2, Lines 21-23):

“Foot orthoses are one of the most used strategies by healthy runners in injury prevention and performance improvement. However, their effect on running kinematics throughout the evolution of an intense prolonged run in this population is unknown.”

2. Line 36-38: I recommend changing the last sentence of the conclusion to be something that can be said about the present study. Additional work can always be done but a more impactful conclusion would reflect what can be learned by the present study. As discussed above, commenting about inter-individual differences may be a good topic to replace this last sentence (see further comment below about the inter-individual differences).

Reply: We would like to thank to the reviewer for this comment. We have changed the last sentence of the conclusion in order to focus more on the present study, as follow (Page 2, Lines 37-39):

“This lack of modifications suggest that a healthy runner population maintains its ideal movement pattern throughout a 20 minute prolonged run, regardless the type of foot orthosis used.”

Introduction

3. Line 45: Please be specific here as to not unintentionally spread speculation. The referenced study seems to be about Achilles tendon injuries alone. Also, please confirm that the findings of this study were indeed that the orthoses prevented injury, which is the statement in the text of the present study. Citations should reference the findings, not the speculation or theories proposed by others.

Reply: We would like to thank to the reviewer for this comment. This sentence has been changed to solve a previous comment, so this cite has been deleted because it does not support the new idea.

4. Line 60: “…no clear evidence…of the effect of foot orthoses on running kinematics” is not clear because the authors described some kinematic variables earlier in this paragraph. Please be more specific as to what is still unknown. Also in this paragraph, the ‘preferred movement path’ is discussed as a follow-up to describing that there is not a lot of evidence regarding spatio-temporal variables. Although both portions of the sentence are true individually, they should not be together because the preferred movement path is less a consideration for spatio-temporal characteristics, and more about joint and segment kinematics.

Reply: We would like to thank the reviewer for this comment. Different modifications were performed to address this comment.

Firstly, the sentence “…no clear evidence…of the effect of foot orthoses on running kinematics” has been modified to be clearer (Page 4, Lines 81-82):

“In this sense, there is a lack of information regarding the kinematic effects of foot orthoses during a prolonged run in the literature.”

Secondly, the sentence about ‘preferred movement path’ has been connected with kinematic adjustments in general and with foot eversion, as follow (Page 4, Lines 70-81):

“By contrast, it has been speculated that foot orthoses could modify spatio-temporal kinematics [18] and angular kinematics during running, due to its usual aim of control of pronation [7,8]. The type of the foot orthosis could also have an influence in kinematic adjustments, expecting better results with custom-made foot orthoses than with prefabricated foot orthoses, due to its individual adaptation [28,29]. However, some authors have found a reduction in foot eversion with custom-made foot orthoses [9,14,30], while others have observed the same effect with prefabricated ones [17,31]. In this point, according to one of the last paradigms postulated by Nigg et al. [23,32], the use of footwear (or foot orthoses in this case) should allow healthy runners to maintain their preferred movement path, so caution should be taken with kinematic alterations, since they will not always be positive.”

Methods

5. The authors described that they tested if the variables were normally distributed but did not describe the results of these tests in the statistical analysis section of the methods or in the results. Please describe which variables, if any, were non-normally distributed and what was done (if anything) to adjust for non-normal data.

Reply: We would like to thank the reviewer for this comment. One sentence of the statistical analysis section has been specified to clarify it (Pages 8-9, Lines 189-191):

“After confirming the normality of the sample in all the variables by the Shapiro Wilks test (P > 0.05), and verifying the sphericity by the Mauchly Sphericity test, the descriptive statistics were extracted.”

Results

6. Line 215-216: The end line 216 which is part of the sentence, “there was no significant main effect…in any of the kinematic variables; however, there was a main effect for…” should be changed to “…in any of the kinematic variables except for a main effect for…”. More simply stated, please change “however” to “except for”

Reply: We would like to thank the reviewer for this comment. The sentence has been changed as proposed.

7. As described in the general/overall comments, it may be beneficial to examine the inter-individual differences.

Reply: We think that the reviewer want to reference the intra-individual and not the inter-individual differences. As discussed in a previous comment, our statistical analysis has examined intra-individual differences (comparing a subject with himself in different conditions).

Discussion

8. Line 250: The findings of the referenced study were not “harmful kinematic alterations.” We do not have enough longitudinal evidence to imply that any cross-sectional study is harmful.

Reply: We would like to thank the reviewer for this comment. The sentence has been modified to clarify, as follow (Page 11, Lines 255-257):

“It is well known that during the evolution of a high intensity run, and consequently, with the development of it, some kinematic alterations related to the likelihood of injury and the performance optimization can occur [24,27].”

9. Line 258: These are the only studies that looked at spatio-temportal parameters with respect to what? Orthoses? These are far from the only prolonged running studies out there. This sentence should be more specific.

Reply: We would like to thank the reviewer for this point. The sentence has been specified, as follow (Page 12, Lines 264-268):

“Only the studies of Lucas-Cuevas et al. [20,21] analysed some spatio-temporal parameters in a continuous running protocol, with three different foot orthosis conditions (similar to those employed in the present work), but only at the beginning and at the end of the run, without looking at their evolution.”

10. Line 275: Need to explain how the methods of referenced study (Wilkinson et al) are similar and different than the present study so the reader can have more context to understand why the results between the two studies are being compared and understand the potential explanation for the differences. Start the paragraph explaining this information rather than bring it in later (i.e. line 279-283).

Reply: We would like to thank the reviewer for this comment. We have modified the knee flexion paragraph, where this occurred, to solve a comment from the other reviewer, so we have removed this reference. However, we have taken this comment into account at other times in the discussion.

Figures and tables

11. There is a typo with the spelling of ‘length’ in Figure 4.

Reply: We would like to thank the reviewer for the correction.

12. It is my personal preference to have the full variable name used as figure titles instead of the abbreviation. That way, I don’t have to remember or look back at what something is, I know it the instant that I look at it.

Reply: We would like to thank the reviewer for this comment. We have removed the abbreviations of the variables names, both in the text and in figures 5 and 6. In addition, we would like to comment that we have corrected the design of Figure 5, because we have found an error in the representation of the error bars.

Reviewer #2: Overall, the manuscript is well-written, with a few areas where the use of English grammar is not quite up to expectations. The authors do well to provide background review of the literature and justification for the study. It seems the gap that the authors hope to fill is the effect of custom orthoses over time-course of an intense continuous run. However, the findings of the study indicate that there was no statistical difference to report. A null finding is not considered a negative thing, but it does substantially reduce the enthusiasm for this study. Additionally, while the authors have provided a thorough treatment of the data and kept their conclusions within the scope of the statistical results, they do tend to overstate potential application of this work in the Conclusion statement. I'm not sure that enough evidence was presented to say that impact reduction with orthoses can be a benefit "without interfering in the running technique or running economy".

Reply: We would like to thank the reviewer for the comment. We have changed the last sentence of the conclusion, as follow (Page 16, Lines 376-378):

“This lack of modifications suggest that a healthy runner population maintains its ideal movement pattern throughout a 20 minute prolonged run, regardless the type of foot orthosis used.”

There are a large number of figures, which are unfortunately not very informative. Figures 1-3 are generally helpful to explain the methods, but the information in Figures 4-6 could easily be placed in a table, or in supplementary material, as they really do not show anything more than what the authors have stated in the text.

Reply: We would like to thank the reviewer for this suggestion, but we consider interesting that the figures 4-6 (data of the variables) appear in the final version in order to contextualize the results obtained. However, if the reviewer considers it necessary, we could add them as supplementary material. We had checked this data in a table and we concluded that the figures will be more comprehensible for readers.

The discussion section is excessively long, with too much revisitation of the previous work. Rather than re-reviewing all of the literature here, the manuscript would be improved with a critical evaluation of the points in the literature which may help explain why the current study resulted in null findings.

Reply: We would like to thank the reviewer for this comment. The review of the literature has been reduced in some cases, and it has tried to improve the explanation of the results.

Attachment

Submitted filename: Response to Reviewers.docx

Click here for additional data file. (47.5KB, docx)

Decision Letter 1

Alena Grabowski

10 Feb 2020

PONE-D-19-28910R1

Effect of custom-made and prefabricated foot orthoses on kinematic parameters during an intense prolonged run

PLOS ONE

Dear Dr. Jimenez-Perez,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

In your revision, please consider revising Figs. 4-6 and/or compile them into tables for clarity, correct the grammatical errors in the manuscript, and discuss and present individual data as well as if there were responders and non-responders.

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We look forward to receiving your revised manuscript.

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Alena Grabowski

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The introduction and discussion are much improved now with a more narrow focus that is within the scope of the study.

Many grammatical errors remain that should be addressed.

The purpose of my previous comment regarding the individual differences was to emphasize that each individual will have a very different response to a given footwear or orthotic condition. I understand the use of repeated measures statistics; however, my comment was a recommendation to show the individual data in the figures and tables (as supplements would be fine) instead of the group means and standard deviations as well as to suggest some discussion regarding if there were responders and non-responders, for example. Revealing that some subjects had more of a response than others may result in an alternative perspective or interpretation of the results than what is currently described in the discussion section.

Reviewer #2: The authors have addressed most of my previous concerns. I still feel that the data presented in Figures 4-6 would be better presented in a table form. With essentially equal means and very high deviation bars, the graphs really don't reveal anything more insightful than what could be shown in a table.

**********

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Reviewer #2: No

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PLoS One. 2020 Mar 26;15(3):e0230877. doi: 10.1371/journal.pone.0230877.r004

Author response to Decision Letter 1

24 Feb 2020

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

In your revision, please consider revising Figs. 4-6 and/or compile them into tables for clarity, correct the grammatical errors in the manuscript, and discuss and present individual data as well as if there were responders and non-responders.

Dear editor, we are grateful for the opportunity to revise our paper. All the comments sent by the reviewers were carefully addressed. All the changes in the edited manuscript are highlighted with red text in the revised submission. We look forward to hearing from your editorial decision.

Reviewers’ comments:

Reviewer #1: The introduction and discussion are much improved now with a more narrow focus that is within the scope of the study.

Reply: We are grateful to the reviewer for this comment.

Many grammatical errors remain that should be addressed.

Reply: The manuscript has been carefully reviewed to correct all grammatical errors.

The purpose of my previous comment regarding the individual differences was to emphasize that each individual will have a very different response to a given footwear or orthotic condition. I understand the use of repeated measures statistics; however, my comment was a recommendation to show the individual data in the figures and tables (as supplements would be fine) instead of the group means and standard deviations as well as to suggest some discussion regarding if there were responders and non-responders, for example. Revealing that some subjects had more of a response than others may result in an alternative perspective or interpretation of the results than what is currently described in the discussion section.

Reply: We would like to thank the reviewer for this comment. Three figures with the percentage of change to each biomechanical variable for each participant, and one table that presents the number of participants that showed a biomechanically relevant change have been added as supplementary material. This is mentioned in the results section (Page 13, Lines 252-254):

“Percent changes of the biomechanical variables for each participant as well as the number of participants that showed a biomechanically relevant change (±10%) [36] regarding the control condition are provided in the Supplementary File.”

In addition, at the end of the discussion, a paragraph has been added regarding individual differences, as suggested (Page 18, Lines 375-385):

“From this point of view, although no differences have been found between the three foot orthosis conditions studied from a grouped perspective, in the studies of foot orthosis and footwear it is common to find a large variability of response among participants, which is masked by the overall results [36]. In the present study, as presented in the Supplementary File, the spatio-temporal parameters have not been affected by inter-subject variability, since most participants have not experienced a relevant change. However, in the angular parameters, the effects of different directions and magnitudes have been observed both among participants as well as within a single individual. In the future, it would be interesting to study if these different responses to a foot orthosis implementation could be grouped by some participant characteristics, such as the gender or the type of foot.”

Reviewer #2: The authors have addressed most of my previous concerns. I still feel that the data presented in Figures 4-6 would be better presented in a table form. With essentially equal means and very high deviation bars, the graphs really don't reveal anything more insightful than what could be shown in a table.

Reply: We would like to thank the reviewer for this comment. The data showed in Figures 4-6 have been presented in tables (Tables 2, 3 and 4, respectively) as suggested.

Attachment

Submitted filename: Response to Reviewers.docx

Click here for additional data file. (15.9KB, docx)

Decision Letter 2

Alena Grabowski

11 Mar 2020

Effect of custom-made and prefabricated foot orthoses on kinematic parameters during an intense prolonged run

PONE-D-19-28910R2

Dear Dr. Jimenez-Perez,

We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements.

Within one week, you will receive an e-mail containing information on the amendments required prior to publication. When all required modifications have been addressed, you will receive a formal acceptance letter and your manuscript will proceed to our production department and be scheduled for publication.

Shortly after the formal acceptance letter is sent, an invoice for payment will follow. To ensure an efficient production and billing process, please log into Editorial Manager at https://www.editorialmanager.com/pone/, click the "Update My Information" link at the top of the page, and update your user information. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

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With kind regards,

Alena Grabowski

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: The authors have adequately addressed my previous concerns. The revised version of the manuscript now reads very clearly and the presentation of results is concise and clear.

**********

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Reviewer #1: No

Reviewer #2: No

Acceptance letter

Alena Grabowski

13 Mar 2020

PONE-D-19-28910R2

Effect of custom-made and prefabricated foot orthoses on kinematic parameters during an intense prolonged run

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Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    S1 Fig. Percent changes relative to control foot orthosis condition for spatio-temporal parameters regardless the time points of the running test.

    (JPG)

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    S2 Fig. Percent changes relative to control foot orthosis condition for knee flexion parameters regardless the time points of the running test.

    (JPG)

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    S3 Fig. Percent changes relative to control foot orthosis condition for foot eversion parameters regardless the time points of the running test.

    (JPG)

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    S1 Table. Number of participants experiencing biomechanically relevant reductions (≥10% Reduction), biomechanically relevant increases (≥10% increase), and no change (change between -9.9% and +9.9%) for each variable, regardless the time points of the running test, when wearing prefabricated or custom-made foot orthoses compared to control condition.

    (DOCX)

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    Attachment

    Submitted filename: Response to Reviewers.docx

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    Attachment

    Submitted filename: Response to Reviewers.docx

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    Data Availability Statement

    Data are available from DOI: 10.17632/ftnk8m3hdd.1 (http://dx.doi.org/10.17632/ftnk8m3hdd.1)

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