Foam rolling is an effective recovery tool in trained distance runners

Abstract

Purpose

Many endurance athletes use foam rolling (FR) to decrease muscle soreness, but it is unclear whether FR effectively treats soreness in this population. Moreover, the effects of FR in highly trained runners are unknown. The aim of this study was to use downhill running (DHR) to induce muscle soreness in runners and to determine the influence of FR on soreness and running performance when compared to sham compression tights.

Methods

Participants performed a running economy (RE) test at 75% of 5-km race speed and a 3-km time trial (TT). In a crossover design, subjects then completed DHR followed by either a FR protocol or wearing sham compression tights. Two days post-DHR, subjects repeated the RE and TT tests. Crossover visits occurred 2–4 weeks later. During RE tests, VO₂ and rating of perceived exertion (RPE) were recorded. Passive and active soreness were measured on a scale of 0 (no soreness) to 10 (extreme soreness).

Results

Eight runners (aged 31 ± 7 years; four females; VO_2peak 57 ± 7 ml kg⁻¹ min⁻¹) completed the study. Both treatment conditions experienced passive (p = 0.026) and active soreness (p = 0.012) induced by DHR. Active soreness 2 days postDHR was significantly lower after FR than after sham compression tights (p = 0.025). With tights, there was a trend for an increased RPE compared to pre-DHR (p = 0.056).

Conclusions

Foam rolling decreases leg soreness in well-trained runners and attenuates soreness-related increases in perceived exertion during sub-maximal running.

Introduction

Exercise-induced muscle damage (EIMD) occurs following unaccustomed exercise, i.e. exercise at an intensity and/or duration greater than that in which the participant has previously partaken, or exercise with a modality new to the user [1]. Eccentric (muscle-lengthening) exercise can also cause EIMD, and exercise that is both novel and eccentric has the greatest potential to damage muscle [1–6]. Exercise-induced muscle damage manifests as alterations in muscle fibers and blood biomarkers. Muscle biopsies from regions injured by damaging exercise show changes in cell structure, including Z-line disturbances, thick filament loss, A-band disturbances, and decreased mitochondrial density [3]. Exercise-induced muscle damage also presents as increased levels of muscle proteins in the blood; loss of muscle force; and muscle swelling, stiffness, and soreness. Creatine kinase (CK) is a muscle protein whose presence in the blood is often used to show that muscle damage has occurred (e.g. [7, 8]), although its kinetics do not match the progression of DOMS [7] or indicate muscle inflammation [9]. Levels of interleukin-1β (IL-1β), a pro-inflammatory cytokine, have been observed to increase in muscle and non-muscle cells after eccentric exercise [7, 10], suggesting that such exercise can induce a systemic inflammatory response.

Exercise-induced muscle damage causes delayed-onset muscle soreness (DOMS). The processes by which EIMD may impair muscle function have been described, but mechanistic pathways leading from EIMD to DOMS remain unclear. Equally noteworthy, relationships between DOMS and changes in physiological variables predictive of sport performance are incompletely understood [11]. Importantly, the sensation of DOMS alone can decrease performance [5]. As such, DOMS is a major focus of research in the fields of exercise physiology and sport performance [1, 3, 12].

Downhill running (DHR), which has a large eccentric component, is commonly used to cause EIMD in a laboratory setting [1, 12–15]. DHR, in addition to other muscle-damaging eccentric exercise protocols, effectively induces DOMS in both trained and untrained individuals [1, 12–18], which makes DHR an appropriate method by which to study muscle soreness in athletes. Because of the potential negative effects of EIMD and DOMS on sport performance [19], athletes whose fitness levels range from recreational to elite continually seek means to decrease soreness while enhancing recovery [6, 20]. Hausswirth and Le Meur [21] have suggested that athletic recovery involves a return to physiological homeostasis after training-induced disruptions. Thus, a recovered athlete is no longer hindered by disturbances to thermoregulation, muscle function, or metabolism and can complete a training session without fatigue or increased injury risk [21].

Recovery techniques used with the intention of returning to pain-free training include massage, compression garments, cryotherapy, contrast baths, hyperbaric oxygen therapy, anti-inflammatory drugs, light exercise, stretching, dietary supplements, and electric stimulation [6, 20]. However, evidence supporting the use of these techniques is equivocal at best, while also showing that some methods may even slow recovery and diminish the physiological adaptations that occur with exercise training [4, 20]. Foam rolling (FR) is a recovery technique that may be effective in mitigating DOMS while also attenuating decreases in performance. In a recent study, strength-trained men completed either a FR sequence or no recovery after a damaging eccentric squat protocol [22]. The participants in the FR group had less soreness and had preserved range of motion, dynamic movement, and muscle activation relative to the control group [23].

Foam rolling is promoted as a recovery tool for the general population as well as serious athletes, including distance runners. Although high-level runners may use FR after strenuous workouts in attempts to decrease feelings of soreness and tightness, no placebo-controlled research to date has examined the influence of FR on recovery in this population. A dearth of studies focused on trained athletes makes it difficult to apply findings from research on untrained individuals to competitive performers. Moreover, no studies have yet implemented a muscle-damaging running protocol while using lab- and field-based tests to assess the effects of EIMD on running performance.

Therefore, the aim of this study was to determine whether FR performed after a bout of damaging exercise (i.e. DHR) would affect soreness and distance-running performance in well-trained runners. We hypothesized that DHR would cause DOMS in all participants [13–15]. We also hypothesized that running performance, as assessed through the oxygen cost of running (running economy [RE]) and time to complete a 3-km time trial (TT), would be adversely affected following DHR [1, 13, 24]. Lastly, we hypothesized that FR would attenuate increases in DOMS and decrements in performance as compared to a placebo (sham) recovery treatment via the beneficial effects of FR on connective tissue [23, 25].

Methods

Study design

The present study was a randomized placebo-controlled crossover design. Studies were performed at the Human Sport Performance Laboratory at the School of Kinesiology at the University of Minnesota, Minneapolis, MN from July to September of 2014. The University of Minnesota’s Institutional Review Board approved the protocols for this study, and all participants provided written informed consent prior to enrollment. Participants reported to the laboratory for seven visits, which are outlined in Fig. 1. At the first visit, the athletes gave informed consent and underwent peak aerobic capacity (VO_2peak) testing and body composition assessment. At the second visit, 2–7 days later, participants performed a RE test and a 3-km TT. At the third visit, which took place 2–4 days after visit 2, subjects completed a DHR and one recovery protocol. The athletes returned approximately 48 h later for visit 4, where they repeated the RE test and TT.

Fig. 1.

Study design. FR foam rolling, DHR downhill running, RE running economy, TT time trial

Visit 5 took place 2–4 weeks after visit 2 for all male subjects. To control for the menstrual cycle, female participants reported to the laboratory for visit 5 four weeks after visit 2. With this schedule, female subjects were in approximately the same phase of their menstrual cycle for each set of visits. The between-treatment period of 4 weeks was chosen so that subjects would still be protected by the repeated bout effect from the first DHR [1]. The randomized crossover design of the study ensured that participants had an equal probability of completing each recovery treatment while experiencing the repeated bout effect. During visits 5–7, subjects repeated the protocols of visits 2–4 but received the opposite recovery treatment in visit 6.

Subjects

Potential participants were included if they were between the ages of 18 and 40, were not pregnant and did not plan to become pregnant during the course of the study (if female), and had run at least 30 miles per week for the preceding 3 months. Exclusion criteria included taking non-steroidal anti-inflammatory drugs more than one time per week or engaging in FR at least once per week. Ten runners (five male, five female) were recruited via informational emails from race organizations and distance running and triathlon online forums.

Procedures

Body composition assessment

The heights and masses of all participants were collected using a stadiometer (ACCUSTAT™ Stadiometer, Genentech, San Francisco, CA) and electronic digital scale (Pro-Doc PD 300, DETECTO, Webb City, MO), respectively. Athletes were unshod and wore spandex shorts; females also wore a sports bra. Body composition was determined using a hydrostatic weighing system (FLOTAWEIGH, EXERTECH, La Crescent, MN). Eight repeat measurements were collected; the highest and lowest percent body fat values were discarded, and percent body fat was calculated as the average of the remaining six values.

Peak oxygen uptake assessment

All treadmill tests were conducted on a Woodway Pro XL treadmill (Woodway, Waukesha, WI). At the first visit, all athletes performed an incremental treadmill test to exhaustion to determine their peak oxygen consumption (VO_2peak). The speed for this test was based on subjects’ self-reported estimated current 5-km race pace [14]. Participants began by walking for 3 min at 5.0 km h⁻¹ (3.1 mi h⁻¹) on a level treadmill. Treadmill grade was then increased to 1%, and speed was increased by 0.64 km h⁻¹ (0.4 mi h⁻¹) in 1-min increments until reaching the 5-km race speed, after which grade increased by 2.5% each minute. Subjects ran to volitional exhaustion. An Ultima CPX cart and BreezeSuite software (MGC Diagnostics, St. Paul, MN) were used for collection and analysis of respiratory gas data throughout the test.

Downhill running protocol

The DHR was used to cause muscle soreness in the participants. DHR was deemed an appropriate means of inducing muscle damage because it simulates conditions that runners might encounter in their daily training [5, 17].

On the first study visit, athletes received a brief (1 min or less) orientation to DHR on the treadmill. For the DHR, the treadmill was inclined to + 10%, and the belt ran backward with subjects facing the rear of the treadmill. This familiarization session was given to acclimate participants to facing the wrong way on the treadmill and to prevent injury.

Prior to the DHR, participants warmed up for 5 min at a self-selected pace on a level treadmill. Athletes then ran downhill for 30 min at 75% of their 5-km race speed.

Running economy assessment

Athletes were instructed to wear the same shoes for each RE test, and these tests occurred at a similar time of day for each participant, as footwear and time of day have been shown to affect RE [26]. Participants were asked to keep logs of what they ate and the activity they did 48 h prior to each RE test, and attempt to replicate these conditions before each RE evaluation, to be as consistent as possible in their diet and training across all tests. Participants were also requested not to engage in strenuous training or resistance exercise in the 48 h prior to RE testing.

Participants were permitted to warm up for 5 min on a level treadmill at a speed less than 65% of their 5-km race pace speed. Following the warm-up, athletes completed a submaximal running stage at a 1% grade and 75% of 5-km race speed. A 1% treadmill grade has been shown to mimic the cost of running outdoors [27]. Participants rated their perceived exertion on a 6–20 Borg scale at 3 min into each stage [22]. Breath-by-breath respiratory gas data were collected throughout the test.

Time trial protocol

A 3-km TT was chosen to evaluate the effects of DOMS and FR on runners’ performance in the field [28]. After at least a 10-min recovery period following the RE test, participants performed the TT on a 400-m outdoor track or a 200-m indoor track. Before commencing the TT, subjects were asked to complete their typical pre-race warm-up, which typically comprised running drills and strides. Each individual participant ran his or her TT on the same type of track at each TT session. Athletes were hand-timed with stopwatches and received verbal encouragement upon completion of each lap.

Muscle soreness assessment

Evaluation of leg muscle soreness took place immediately before DHR, immediately after DHR, and before the RE post-test (i.e. in visits 4 and 7). Participants responded verbally to the question “On a scale of zero to ten, where zero is no soreness and ten is the worst soreness you can imagine, how sore are your legs right now?” This scale has previously been used in studies of DOMS (e.g. [29]). Both passive and active soreness were assessed. To evaluate passive soreness, subjects stood upright and motionless. To evaluate active soreness, subjects stepped down from a rigid chair, 45 cm in height, two times, once from each leg, before rating their soreness.

Recovery protocols

Immediately after completing the DHR, participants performed one of two recovery protocols.

1. Foam rolling: participants used a dense foam roller 6″ in diameter and 12″ long (OPTP Axis, Minneapolis, MN). This density was chosen because denser rollers have been shown to be more effective than less dense ones [30]. The FR protocol is based on the work of MacDonald, Button, Drinkwater, and Behm [23] and consisted of two sets of 4 min per leg (16 min total). Athletes rolled the front (quadriceps muscles), lateral part (IT band), and back (hamstrings) of each leg, as well as the gluteal muscles, for 1 min per muscle group. Participants received instruction on proper technique and were told when to switch muscle groups. To perform rolling of the front, back, and side of their legs, participants placed the roller slightly distal to the hip and rolled in undulating motions until reaching just proximal to the knee. They then rolled back up to the hip in one motion. They repeated this procedure for the entirety of each 1 min interval.

2. Tights: participants were asked to don Filament running tights in the size that they normally wear (Nike, Beaverton, OR). To control for the placebo effect, they were told that these were compression tights, which are commonly perceived as aiding in recovery. Research staff instructed participants to choose a size that felt tight so that subjects would experience a similar feeling to that of true compression tights. Athletes were blinded to the brand and design of the tights. Participants wore the tights and sat quietly for 16 min, an equivalent duration to the FR protocol. Following the completion of the study, subjects were informed that these were not real compression tights and were given the opportunity to withdraw their data from the study; however, none did.

Evaluation of muscle damage and inflammatory markers

Plasma levels of IL-1β and CK were used to determine the presence of muscle damage and inflammation. Blood was drawn from the antecubital vein immediately before and after each DHR and prior to the RE tests in visits 4 and 7. Samples were collected in heparinized Vacutainer tubes (BD, Franklin Lakes, NJ) and centrifuged at 1000 × g (Eppendorf, Hauppauge, NY) for 30 min. Aliquots were stored at − 80 °C before analysis.

To quantify plasma levels of IL-1β and CK, enzyme-linked immunosorbent assay kits from BD Biosciences (San Jose, CA) and Bioassay Systems (Hayward, CA), respectively, were used according to the manufacturers instructions. Analysis was performed using a BioTek spectrophotometer (Winooski, VT).

Data analysis

To determine VO2peak, mid five-of-seven averaging of the breath-by-breath data recorded by the BreezeSuite software was used. RE was calculated as the average VO2 recorded in the final 2 min of the sub-maximal running test, when the participants had reached steady-state running. Rating of perceived exertion on a 6–20 scale [22] was reported from the third minute of the RE test.

Statistical analyses

Because this is a pilot study, previous research using the comparisons of the present study in well-trained runners was not available to guide statistical considerations. Therefore, no power analysis was conducted. However, based on sample sizes in other studies of highly trained runners, we aimed to enroll ten subjects.

Statistical Package for the Social Sciences (SPSS) version 22 (IBM, New York, NY) was used for analyses. Descriptive statistics were reported as mean ± standard deviation. Repeated measures two-way ANOVAs were used to compare between-group soreness ratings, running performance variables, and biomarker levels at each time point. The factors were treatment (FR or sham tights) and time (pre-DHR, post-DHR, and 48 h post-DHR). The alpha level for significance was set at p < 0.05. Additionally, Cohen’s d was calculated to evaluate effect sizes comparing changes in passive and active soreness, RE, RPE, and TT time from pre-DHR 48 h post-DHR between treatments.

Results

Two participants (one male, one female) dropped out for injuries unrelated to the study after completing four visits and were not included in the analysis. In total, eight participants completed the study. Due to difficulty in drawing blood, we were unable to obtain a complete set of samples from two subjects. Only assay data from subjects whose blood was collected at all time points were included in analysis. The sample size for the analysis of inflammatory markers was six. Demographic characteristics of the participants appear in Table 1. Effect sizes (Cohen’s d) comparing the effects of FR and tights on muscle soreness and running performance variables are reported in Table 2. Foam rolling had large and positive effects on mitigating DHR-induced elevations in muscle soreness and RPE.

Table 1.

Demographic characteristics of the participants

Characteristic	Females (n = 4)	Males (n = 4)	All (n = 8)
Age (years)	30 ± 6	32 ± 9	31 ± 7
Height (cm)	165 ± 6	179 ± 9	172 ± 10
Mass (kg)	62 ± 15	76 ± 9	69 ± 13
BMI (kg m−2)	23 ± 4	24 ± 5	23 ± 5
Body fat (%)	22 ± 7	14 ± 12	18 ± 10
VO2peak (ml kg−1min−1)	54.9 ± 3.7	59.1 ± 9.6	57.0 ± 7.1

Data are presented as mean ± standard deviation

BMI body mass index, VO_2peak peak aerobic capacity

Table 2.

Effect sizes comparing changes in muscle soreness and running performance at pre-DHR and 48 h post-DHR between recovery conditions

Variable	Cohen’s d
Passive soreness	1.15
Active soreness	0.86
RE	0.23
RPE	0.97
TT	0.10

DHR downhill run, RE running economy, RPE rating of perceived exertion, TT time trial time

Muscle soreness

Figures 2 and 3 display results for passive and active soreness, respectively. The runners rated their soreness on a scale of 0–10. The mean passive muscle soreness ratings of participants in the FR condition were 1.5 ± 1.2 prior to the DHR, 3.0 ± 1.7 immediately after the DHR, and 2.1 ± 1.5 at 48 h after the DHR. In the tights condition, passive muscle soreness at the same time points was reported as 1.8 ± 1.2, 3.5 ± 1.9, and 3.8 ± 1.2, respectively. There was not a significant main effect of treatment (p = 0.115) on passive soreness. However, the effect of time on passive soreness was significant (p = 0.026). There was not a significant treatment × time interaction (p = 0.184).

Fig. 2.

Passive soreness. DHR downhill running. ^main effect of time, p = 0.026

Fig. 3.

Active soreness. DHR downhill running. ^main effect of time, p = 0.012; *main effect of treatment, p = 0.025

In the FR condition, athletes rated their active muscle soreness as 1.8 ± 1.4 before the DHR, 4.2 ± 1.9 immediately post-DHR, and 3.1 ± 1.9 at 48 h post-DHR. For tights, reported active soreness was 2.7 ± 1.3, 4.4 ± 2.0, and 5.4 ± 0.9 at these time points. The main effect of treatment on active soreness was significant (p = 0.025), as was the effect of time (p = 0.012). The treatment × time interaction was not significant (p = 0.102).

The significant main effect of time on passive and active soreness shows that in both recovery conditions, participants did incur soreness via the DHR. However, FR reduced active muscle soreness over time more than did wearing sham compression tights.

Running performance

All participants completed the RE tests and the 3-km TT. Table 3 shows values of the running performance variables (VO₂, RPE, and TT time) as measured before and after DHR. Figure 4 displays the percent changes in these variables from pre-DHR to 48 h post-DHR in the FR and tights conditions. The percent changes in the running performance variables were not significantly different between recovery treatments (p > 0.05 for all comparisons). There was no main effect of time or treatment, nor was there an interaction, for any of these variables.

Table 3.

Sub-maximal running performance variables before and after downhill running

		VO2 (ml kg−1 min−1)	RPE (6–20)	TT time (min)
Foam rolling	Pre-DHR	37.10 ± 1.68	10.5 ± 0.63	12.36 ± 0.72
	48 h post-DHR	36.86 ± 1.94	10.75 ± 0.73	12.66 ± 0.82
Tights	Pre-DHR	36.22 ± 2.30	10.75 ± 0.70	12.15 ± 0.61
	48 h post-DHR	36.38 ± 2.23	12.00 ± 0.38	12.49 ± 0.73

Data are presented as mean ± standard error

DHR downhill running, VO₂ rate of oxygen consumption, RPE rating of perceived exertion, TT time trial

Fig. 4.

Percent change in running performance variables with downhill running. VO₂ oxygen consumption, RPE rating of perceived exertion, TT time trial. Error bars show standard error

Running economy

Running economy was defined in the present study as the oxygen cost of running (VO₂, ml kg⁻¹ min⁻¹) at a given submaximal speed. Following DHR, oxygen consumption did not change significantly at 75% of participants’ 5-km race speed with either recovery treatment (p > 0.05). Thus, neither the DHR nor the post-DHR recovery treatment affected the oxygen cost of sub-maximal running.

Rating of perceived exertion

During sub-maximal running, there was a trend toward a significant main effect of treatment (p = 0.056), with FR showing a lower RPE than tights at 48 h post-DHR, and the main effect of time was significant (p = 0.014). There was not a significant treatment × time interaction (p = 0.121). Interestingly, the percent change in RPE in the higher-intensity stage after the sham tights protocol was large and positive while the change after FR was small and negative; however, this result was not statistically significant.

Time trial

Time trial performance pre- and post-DHR did not differ significantly between conditions. The main effect of treatment was not significant (p = 0.183), although there was a trend toward a main effect of time (p = 0.072). The interaction between treatment and time was not significant (p = 0.664). With both recovery conditions, participants tended to run more slowly in the post-DHR TT, but using FR as opposed to sham compression tights did not mitigate increases in TT time.

Muscle damage and inflammation

No IL-1β was detected in any plasma samples, indicating that DHR does not cause systemic inflammation in trained runners. Figure 5 shows the changes in plasma CK levels that occurred with DHR. Creatine kinase levels were not affected by treatment (p = 0.805) or time (p = 0.384). There was not a significant interaction between recovery treatment and time (p = 0.734). Furthermore, the lack of difference in pre-DHR CK values shows that participants returned to baseline CK levels during the two- to four-week period between DHR bouts.

Fig. 5.

Changes in creatine kinase levels with downhill running. DHR downhill running

Discussion

In the present study, we found that FR significantly improves conditions of soreness following DHR. This mitigation may be associated with a lower perceived exertion during submaximal running. Despite the lack of statistical significance in the effect of FR on preventing a soreness-related increase in sub-maximal RPE, the difference between RPE after using FR and wearing sham compression tights was large, as expressed using Cohen’s d. Delayed-onset muscle soreness is a serious concern for athletes, and attenuating its effects may preserve athletic performance. Athletes who experience muscle soreness after EIMD have an increased injury risk due to biomechanical alterations, loss of strength, and reliance on compensation from undamaged muscle groups [2, 14]. Athletes who are not fully recovered from a prior bout of exercise can neither compete to their highest ability nor train at desired levels [20].

Unaccustomed eccentric exercise places a high mechanical load on muscle fibers, causing structural damage [1, 5, 31]. This damage then triggers an inflammatory response, ultimately leading to intramuscular edema, stiffness, and pain [3, 5, 6, 19]. Force production in affected muscles is diminished immediately after exercise, and force decrements may last up to 14 days [2–5]. Muscle soreness peaks 24–48 h post-exercise, but its recovery timeline does not match that of force generation [3–5, 11], suggesting that DOMS alone cannot account for functional impairment.

Most modalities currently used to aid recovery are ineffective at enhancing the rate at which DOMS symptoms abate, while also potentially hindering recovery and limiting exercise adaptations [20, 32–34]. Studies demonstrating the efficacy of various recovery techniques are often limited by the use of non-athlete participants [20, 34–37]. These studies also frequently lack an appropriate placebo control [23, 25, 36], which limits the interpretability of observations [38]. In contrast, the present study included a placebo control, which strengthens the conclusion that FR is effective in promoting recovery from DOMS. Notably, our study participants were highly trained runners, most of whom had previously completed at least one marathon. We aimed to recruit well trained athletes, as this population is most likely to use athletic recovery methods such as FR. Although greater exercise responses could be expected from untrained subjects, the use of trained participants provides insight as to whether FR is, in fact, effective in reducing DOMS symptoms in athletes. One would expect to find differences in responses to exercise or recovery stimuli in nonathletic subjects given their untrained status. However, developing recovery protocols from which athletes actually benefit requires the recruitment of trained participants, whose habitual activities may inure them to a large physiological response to DHR or recovery. Our observation that FR attenuates muscle soreness in athletes supports the use of this modality to enhance recovery from muscle-damaging exercise.

Previous research shows that DHR causes DOMS in runners of various training levels [12–14]. Therefore, it is not surprising that DHR for 30 min at a − 10% grade and sub-maximal intensity—comparable to other DHR protocols—induced soreness in our participants. In both periods of the crossover design, participants reported higher passive and active leg-muscle soreness after the DHR than at baseline. However, the recovery treatment that the runners received had an impact on feelings of soreness. The athletes felt significantly less active soreness after FR than they did after wearing the sham compression tights. Moreover, FR reduced active soreness over time more than the sham treatment did. These results suggest that FR effectively mitigates EIMD-induced increases in DOMS compared to a placebo treatment.

The DHR bout had no effect on sub-maximal VO₂, which we used to represent RE, in this group of well-trained runners. With both recovery protocols, the subjects did not exhibit higher VO₂ in the post-DHR RE assessment than they did at baseline. These results are consistent with other studies, which have found no effects of EIMD on VO₂ [12, 17, 18, 31]. In contrast, some investigators have observed impaired RE with EIMD [13, 15, 24]. Chen et al. suggest that changes in RE with EIMD may be intensity-dependent, as they observed that participants’ VO₂ was higher only at 80% and 90% of VO_2max but not at 70% [15]. In the present study, based on average VO₂ values during the RE tests at 75% of 5-km race speed, participants were running at approximately 65% of their VO_2max in these tests. This intensity therefore may not have been high enough to elicit decrements in RE. Future work exploring the interactions between DOMS, recovery modalities, and running performance should aim to evaluate RE at a percent of VO_2max rather than at a percent of 5-km race speed.

Because participants in the current study were experienced runners, they may also have been able to benefit from the repeated bout effect. Most runners encounter some downhill terrain on their daily routes, and some also engage in resistance training, which can cause EIMD. Previous exposure to EIMD can confer protection from symptoms of later EIMD [1, 3, 5, 24]. We consider that RE of the participants might have been impaired due to EIMD when they began their habitual running programs, but given the consistency with which they currently train, the present DHR stimulus may not have affected their RE. Additionally, there was no effect of treatment on VO₂ measured at 75% of 5-km race speed. This finding shows that the use of FR or sham recovery tights did not affect RE in these subjects at the given workload.

Athletes’ perceived effort level during exercise can affect athletic performance because a higher perceived exertion level is associated with a lower level of exercise tolerance [39]. Furthermore, EIMD can increase the mental effort needed to attain a desired intensity [20]. It was therefore important to measure subjects’ RPE as this measure could relate to diminished performance in the field.

Rating of perceived exertion was elevated after the DHR during sub-maximal running in both recovery conditions. In the FR condition, athletes reported a lower RPE than after wearing the sham tights, although this difference was not statistically significant (p = 0.056). However, given the small sample size of the present study, this finding may have practical significance. The use of FR as a recovery treatment can attenuate EIMD-associated increases in perceived exertion that occur at higher running intensities. Feeling less sore may allow athletes to feel that they are expending less effort during submaximal running.

Participants in the current study completed a 3-km TT as a means of evaluating their performance in the field. Post-DHR, there was a trend for impaired TT performance compared to pre-DHR, but there was no difference in TT performance between recovery conditions. In the present study, neither DOMS nor methods used to attenuate its symptoms affected field-based running performance. In contrast, a recent study found that in strength-trained men who had undergone a damaging squatting protocol, FR maintained vertical jump performance compared to receiving no recovery treatment [23]. The discrepancy between those findings and our observations may be due to the nature of the EIMD protocol and to the methods used to assess athletic performance. The work by Macdonald et al. [23] was also not placebo-controlled, which may have contributed to a positive psychological effect of FR on performance.

Interleukin-1β did not appear in detectable quantities in the blood samples of any participants. Because this cytokine is associated with inflammation, it does not appear that the DHR or either recovery treatment caused a systemic inflammatory response in the participants. Furthermore, CK levels did not change significantly over time or differ between recovery conditions. Elevations in creatine kinase are often used to show that muscle damage has occurred, but CK levels are not well related to DOMS symptoms [11]. Creatine kinase did increase somewhat, although not significantly above baseline, after the DHR, showing that the runners may have incurred some degree of muscle damage. Our finding that the participants had greater muscle soreness after the DHR, in conjunction with the failure of CK to rise significantly, further discourages the use of this biomarker to evaluate muscle damage.

Our findings demonstrate that FR leads to diminished feelings of EIMD-related soreness as compared to a placebo treatment. Although research has not yet elucidated the physiological pathways by which FR exerts its effects, several potential mechanisms have been proposed. In a recent study by MacDonald et al. [23], subjects who performed FR demonstrated larger decrements in evoked contractile properties and peak twitch force of the treated muscles than controls, suggesting that FR does not promote recovery of the muscle itself. However, the FR group had higher voluntary muscle activation than controls, better-preserved vertical jump height, and evidence of better functioning of series elastic components in muscle, suggesting that FR aids in connective tissue recovery and allows athletes to activate more muscle fibers to attenuate force losses from damaged fibers [23].

Foam rolling is also known as self-myofascial release. Myofascial release is a type of massage that aims to break up fascial adhesions caused by injury or inflammation. These restrictions can be painful and limit athletic performance. Theoretically, FR can release such adhesions in the same manner as myofascial release [40, 41].

Foam rolling may also act by some of the same proposed anti-inflammatory pathways as massage therapy [23, 25, 30, 40, 41]. After muscle damage, neutrophils infiltrate injured areas, where they ingest tissue debris as well as healthy tissue, thereby causing further damage [3, 6, 35]. This damage, with additional inflammation that accompanies EIMD, sensitizes group III and IV afferent nerves, contributing to feelings of DOMS [2, 3, 35].

A study of massage therapy performed 2 h after damaging exercise found that massage decreased neutrophil infiltration (as assessed through circulating neutrophils), which could slow inflammation and lessen DOMS symptoms [42]. Moreover, a recent study [43] evaluated the effects of a 10-min massage on trained cyclists after an intense cycling exercise. In the massaged subjects, the authors observed an increase in signaling from PGC-1α, an anti-inflammatory modulator that is involved in mitochondrial biogenesis, as well as an attenuated response from NFκB, a pro-inflammatory signaling pathway [43]. However, another study found that massage after EIMD did not affect circulating neutrophils in spite of lower reported soreness in the massage group compared to controls, leading the authors to conclude that the effects of massage are likely more psychological than physiological [35].

The conflicting results regarding massage therapy and inflammation, as well as the lack of research pertaining specifically to the physiology of FR, warrant further investigation of the mechanisms underlying FR.

In a potential limitation of this study, participants reported muscle soreness on an 11-point (0–10) verbal scale. While other studies on EIMD have used such a scale [29], it is possible that a visual analog scale (e.g. [14, 15, 18]) would have produced more reliable results than a verbal scale. Some studies have also used muscle palpation or other physical manipulation of the muscle to evaluate soreness [16, 17]. However, subjective and objective ratings of pain are related [44], and therefore the use of a verbal scale likely did not contribute to major inaccuracies in soreness reporting.

Seven out of eight athletes in the current study were marathon runners, and most participants had not recently trained at the level of intensity demanded by the 3-km high-effort TT. They might, therefore, have benefited from a learning effect during the course of the study. It is likely that they developed more efficient pacing strategies that allowed them to improve their performance over the four trials that they completed (or to maintain their performance in spite of having incurred EIMD). This development could have masked decrements in performance that occurred with DOMS, especially if subjects did not perform to their full capabilities in pre-testing TT efforts. The randomized crossover design of the study was designed to account for such an effect, but it is possible that performing a familiarization TT prior to testing could have revealed larger between-treatment differences in TT time with DHR.

To the best of our knowledge, this study is the first to demonstrate that FR effectively manages muscle soreness in athletes compared to a placebo control. Furthermore, we are the first to show the benefits of FR in a highly trained distance-running population. The randomized crossover design accounts for the repeated bout effect and TT learning effect. Despite our small sample size, our findings of significant between-treatment differences in soreness and promising observations regarding RPE during running encourage further research into the use of FR in distance runners to improve or preserve performance.

Conclusion

In conclusion, we demonstrate that an acute bout of FR done immediately after completion of a muscle-damaging DHR has beneficial performance-related effects in well-trained runners. Relative to a sham recovery treatment, FR can attenuate increases in active muscle soreness after the damaging exercise bout. Additionally, FR may mitigate a DOMS-associated increase in RPE during a sub-maximal running bout.

Practical applications

One 16-min FR protocol performed after a soreness-inducing DHR is adequate to promote recovery in trained endurance athletes. Foam rolling can be considered an effective recovery tool for runners because it can alleviate muscle soreness without negatively affecting running performance.