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. 2020 Aug 21;18(3):198–204. doi: 10.1016/j.jcm.2019.01.003

Mixed Modal Training to Help Older Adults Maintain Postural Balance

Amanda Marchini a, Wellington Pedroso a, Osmar Pinto Neto b,⁎
PMCID: PMC7452169  PMID: 32874159

Abstract

Objective

Older adults have poorer balance compared with younger adults, but exercise may slow this age-related loss. Although the best type of exercise to optimize balance gains remains unclear, it is likely that a training regimen incorporating several different types of exercise, termed mixed modality training (MMT) (popularized by CrossFit), would be effective. Accordingly, this study aims to assess whether regular MMT leads to improved balance in older adults.

Methods

Ten trained young (28 ± 4 years, minimum of 1 year MMT) and 22 older (67 ± 6 years) adults participated in this study. Older adults were divided into 2 groups: trained (minimum of 1 year MMT) and untrained. An electronic baropodometer was used to assess baseline postural balance using the postural sway (both open and closed eyes) test.

Results

Compared with untrained older adults, those who trained performed similarly to young trained adults in the postural sway test. In addition, with eyes closed, trained older adults demonstrated better center of pressure total displacement area than untrained older adults.

Conclusion

These data suggest that regular MMT can lead to a level of postural control in older adults similar to that observed in young adults. The favorable effects of MMT on postural control in older adults may be attributable to improvements in both muscle strength and proprioception.

Key Indexing Terms: Aging; Exercise; Posture; Physical Conditioning, Human

Introduction

The postural control system comprising the motor, sensory, and nervous systems plays a key role in maintaining body balance. However, balance decreases during the transition from young to late adulthood.1, 2, 3 This decrease in balance associated with adult aging has been identified as a primary cause of falls, which are associated with increased mortality.4 Nevertheless, with regular exercise training, progressive decreases in balance may be slowed during the aging process.1, 2, 3, 4, 5, 6, 7

The physiological changes associated with aging, and particularly those associated with balance, become more apparent at around 45 years of age and continue to worsen progressively over time.1, 2, 3, 4 These changes occur in both the sensory system (visual, vestibular, and somatosensory) and in physical function (flexibility, strength, balance, and coordination). These age-related changes are known to affect reaction time, causing older adults to develop balance-related issues. In this context, regular physical activity may be an effective strategy to improve balance control while also reducing the incidence of falls in older adults.5 Several studies have demonstrated the favorable effects of proprioceptive exercise on postural balance by increasing or decreasing body sway.6,7 Others have suggested that basic strength training protocols that target specific muscle groups (eg, calf muscles) may be effective in improving balance in older adults.8,9

However, an approach that combines several physical training modalities in a single program, for example, mixed modality training (MMT), has never been tested for this purpose.

Mixed modality training has been popularized in both military and civilian communities in recent years as a method to improve fitness and health. This is largely due to its promotion by several popular trademarked exercise programs (eg, CrossFit, Insanity, Gym Jones10,11). Despite this popularity, professional associations in the fields of sports science and medicine remain unclear about the implementation of MMT in therapeutic settings,12,13 and no study to date has tested what effect MMT might have on changes in balance.

This study aims to address this question of whether regular participation in MMT may cause differences in balance between trained and untrained older adults. We hypothesize that older adults who participate in regular mixed modal high-intensity training will exhibit better postural balance control than their untrained counterparts.

Methods

This was an analytic cross-sectional retrospective observational study. Young and older adults were recruited in 3 discrete groups to participate in the study. In the first group, 10 trained young adults (28 ± 4 years) were recruited from a local fitness center (São José dos Campos, Sao Paolo, Brazil). In the second group, 10 trained older adults (66 ± 6 years) were recruited from a municipal program where they had participated in a mixed modal training schedule for at least 1 year. Finally, for the third group, 12 (68 ± 6 years) untrained older adults (control) were recruited from the same municipal program. This group participated in different leisure-only activities such as painting, chess, and playing cards, but no physical activities. No participant demonstrated abnormal vision or neurologic conditions. Written informed consent was obtained from all participants before testing. All aspects of this study were reviewed and approved by Unicastelo University. Tests of motor control were performed on these participants and have been previously reported in Marchini et al.14

Sample Size Computation

The calculations to establish the sample size were performed with the program GLIMMPSE (http://glimmpse.samplesizeshop.org/), as recommended by Guo et al (2013).15 Sample size calculations are fundamental to allow a reasonable power to detect at a given level of statistical significance, a predetermined difference (effect size) in the outcome variable.16 We computed the sample size for a repeated measures design of 2 factors, 3 groups (young trained adults, older trained adults, and older untrained adults), 2 conditions (eyes open vs eyes closed), and an interaction hypothesis that considered between- and within-participant factors. In addition, we used the Hotelling-Lawley trace test.17, 18, 19 Power was set at 80%, the significance level at α = 0.05, and effect sizes were estimated considering mean and variability results from Table 1 of Melzer et al (200120) and Table 2 of Melzer et al (200421). From the first table, 5 different variables for single task postural stability standing with wide base (young and old age groups) were used. From the second table, the same variables were found for non-faller older adults with wide-base stance, eyes open and eyes closed. Finally, correlation among postural stability variables was set to 0.8 considering data previously collected by the authors.3 With all these considerations, GLIMMPSE estimated an actual power of 0.85 and total sample size of 27. This sample size was estimated considering a further parametrical statistical test. However, the participants within the groups were recruited from a single location, which implied the need for a nonparametric statistical analysis of the data collected. We therefore applied a correction of 15% to the total value, as suggested by Lehmann (1998),22 successfully recruiting the indicated minimum of 31 participants.

Table 1.

Median and IQR Results Obtained From the Young Adults (n =10) and the Trained (n =10) and Untrained (n =12) Adults During the Standing Still Postural Sway Test With EO and EC

Variables Trained Young Adults Trained Older Adults Untrained Older Adults
Dap (mm) EO: 1.17 (0.84-1.82)
EC: 1.98 (1.30-2.87)		 EO: 1.22 (0.65-1.72)
EC: 2.37 (1.25-3.74)		 EO: 1.48 (1.31-2.10)
EC: 3.94 (2.25-7.70)
Dml (mm) EO: 1.05 (0.69-2.42)
EC: 1.68 (1.01-2.96)		 EO: 1.25 (0.86-2.02)
EC: 1.96 (1.31-3.24)		 EO: 1.79 (1-2.21)
EC: 3.06 (2.37-5.51)
Dt (mm) EO: 77.84 (39.02-116.86)
EC: 107.94 (75.80-166.35)		 EO: 64.50 (41.36-100.07)
EC: 125.35 (76.84-204.92)		 EO: 94.26 (71.43-126.04)
EC: 208.83 (141.20-352.43)
Vt (mm/s) EO: 0.52 (0.41-0.61)
EC: 0.64 (0.47-0.73)		 EO: 0.40 (0.30-0.57)
EC: 0.51 (0.38-0.86)		 EO: 0.50 (0.38-0.62)
EC: 1.07 (0.63-1.36)
Area (mm2) EO: 1.09 (0.39-2.00)
EC: 2.48 (1.10-5.29)		 EO: 1.14 (0.29-2.40)
EC: 3.21 (1.14-9.71)a 		EO: 1.64 (1.24-4.36)
EC: 11.33 (4.45-25.51)a
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Area, total COP displacement area; Dap, anterior-posterior COP displacement amplitude; Dml, mid-lateral COP displacement amplitude; Dt, total COP displacement; EC, eyes closed; EO, eyes open; IQR, interquartile range; Vt, total COP average velocity.

a

Statistically significant difference between trained and untrained older adults with eyes closed (P = .009).

Training Experience

Adults in the trained group had performed MMT for a minimum of 1 year. Workouts for MMT were divided into 4 stages: warm-up, skill development, workout, and recovery. The warm-up was used to prepare participants mentally and physically for the training stage, as well as for stimulating increased blood flow to muscles, body temperature, metabolic activity, and limb range of motion.23 The second stage consisted of strength and/or power training with barbells and dumbbells, using maximum, repetitive stress, and dynamic efforts and, less frequently, bodyweight exercises such as push-ups and pull-ups.24 The third stage was the workout, which typically involved a novel sequence of 1 or more exercises performed at high intensity. Four training protocols were commonly used in this stage: maximum effort training, interval training, endurance training, and circuit training.25 The exercises primarily used for strength training were squat, deadlift, bench press, press, and power clean. The most commonly used protocol was 3 sets of 5 repetitions using the highest load tolerable without compromising technical form.26 The final stage consisted of stretching and flexibility work.

Testing Protocols

Postural balance was assessed with a postural sway test on an electronic baropodometer force platform.27 Participants stood barefoot on the platform with feet parallel and 10 cm apart. They were asked to remain motionless while gazing at an eye-level mark on the wall. Static standing balance was then registered for a period of 10 seconds with eyes open, followed by 10 seconds with eyes closed.27

Data Collection

Data were collected using an electronic baropodometer (S-Plate Medicapteurs, France) with 1600 sensors and an active surface of 400 × 400 mm, measuring 610 × 580 × 4 mm, and weighing 6.8 kg. Signals were sampled at 20 Hz and processed using a low-pass filter (6 Hz cutoff frequency). Five center of pressure (COP) sway kinetic variables20 were computed using MATLAB R2017a (MathWorks, Inc)28: Dap (mm): anterior-posterior COP displacement amplitude, Dml (mm): mid-lateral COP displacement amplitude, Dt (mm): total COP displacement, Vt (mm/s): total COP average velocity, and area (mm2): total COP displacement area.

Statistical Analysis

We used the ARTool version 1.6.2 (Jacob O. Wobbrock, PhD) to perform an aligned rank transform (ART). An ART relies on a preprocessing step that aligns data before applying averaged ranks, after which point common analysis of variance (ANOVA) procedures can be used.29 After transformation, a 2-way ANOVA with repeated measures was performed to investigate the main effects group (young trained adults, untrained older adults, trained older adults) and condition (eyes open vs eyes closed) and the interaction group vs condition. Tukey's procedure was used for all post hoc analysis. The ANOVAs were performed with the PASW Statistics 18.0 package (SPSS Inc, Chicago, Illinois). The alpha level for all statistical tests was 0.05. Data are reported as median and interquartile range, the distance between the 25th and 75th percentiles within the test.30 Box plots were drawn using SigmaPlot for Windows (Systat Software Inc, Chicago, Illinois) with the standard method of linear interpolation to determine the percentile values. Only the significant main effects and interactions are presented, unless otherwise noted.

Results

Table 1 of the present article shows data from trained young adults and both trained and untrained older adults during the postural sway test with open and closed eyes. Two-way ANOVA after the aligned rank transformation indicated that there was a group main effect for midlateral COP displacement amplitude (F2,31 = 7.22, P = .030). Post hoc analyses indicated that the values were larger for the untrained older adults compared with the trained young adults (P = .047) and for the trained and untrained older adults (P = .004) (Fig 1).

Fig 1.

Fig 1

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Box plot of the midlateral (ML) center of pressure (COP) displacement amplitude (mm) of trained young adults and trained and untrained older adults during motionless standing. The boundary of the box closest to 0 indicates the 25th percentile, the line within the box marks the median, the dashed line marks the mean, and the boundary of the box farthest from 0 indicates the 75th percentile. Error bars above and below the box indicate the 90th and 10th percentiles, and the dots indicate the outlying points. *Statistically significant difference between the trained young adults and the untrained older adults (P = .047), and between the trained and untrained older adults (P = .004).

Post-ART ANOVA also indicated a group main effect for total COP displacement (F2,31 = 9.503, P = .001). In this case, post hoc analyses indicated that the values were larger for the untrained older adults compared with the trained young adults (P = .030) and for the trained young adults compared with the trained older adults (P = .001) (Fig 2).

Fig 2.

Fig 2

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Box plot of the center of pressure (COP) total displacement (mm) of trained young adults and trained and untrained older adults during motionless standing. The boundary of the box closest to 0 indicates the 25th percentile, the line within the box marks the median, the dashed line marks the mean, and the boundary of the box farthest from 0 indicates the 75th percentile. Error bars above and below the box indicate the 90th and 10th percentiles, and the dots indicate the outlying points. *Statistically significant difference between the trained young adults and both other groups (P < .03).

For the total COP, average velocity ANOVA post-ART also yielded a group main effect (F2,31 = 9.244, P = .001). Further post hoc analyses indicated that the values were larger for the untrained older adults compared with the trained young adults (P = .001) (Fig 3).

Fig 3.

Fig 3

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Box plot of the center of pressure (COP) total average velocity (mm/s) of trained young adults and trained and untrained older adults during motionless standing. The boundary of the box closest to 0 indicates the 25th percentile, the line within the box marks the median, the dashed line marks the mean, and the boundary of the box farthest from 0 indicates the 75th percentile. Error bars above and below the box indicate the 90th and 10th percentiles, and the dots indicate the outlying points. *Statistically significant difference between the trained young adults and the untrained older adults group (P = .001).

Finally, for the total COP, displacement area ANOVA after transformation of the data indicated both a group main effect (F2,31 = 17.755, P < .001) and a significant eyes vs groups interaction (F2,31 = 5.423, P = .010). Post hoc analyses indicated that for the area measurements, values differences between trained and untrained older adults were greater for the eyes closed condition (P = .009) (Fig 4).

Fig 4.

Fig 4

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Box plot of the center of pressure (COP) total area (mm) of trained young adults (TY) and trained and untrained older adults (TO and UTO) during motionless standing with eyes open (EO) and closed (EC). The boundary of the box closest to 0 indicates the 25th percentile, the line within the box marks the median, the dashed line marks the mean, and the boundary of the box farthest from 0 indicates the 75th percentile. Error bars above and below the box indicate the 90th and 10th percentiles, and the dots indicate the outlying points. *Statistically significant difference between the trained and untrained older adults (P = .009).

Discussion

The ability to maintain body balance is important for humans, particularly older adults, for whom a fall may have serious consequences. This ability decreases as adults age, but regular exercise training may mitigate this age-related change. Therefore, this study aimed to assess whether regular participation in MMT may lead to improved postural balance in older adults. Our main findings were as follows: (1) postural sway test outcomes suggested worse performance in untrained older adults compared with both trained young adults and trained older adults; and (2) with eyes closed, total COP displacement area measurements were significantly worse in untrained older adults than in trained older adults.

Several of our outcomes confirm that despite age, trained older adults demonstrate similar performance in the postural sway test compared with younger counterparts (Fig. 1-3). These data are consistent with reports of several other studies1, 2, 3, 4, 5, 6, 7, 8, 9 suggesting that exercise training may be effective for attenuating the effects of aging on postural balance control. With this, for the first time, we demonstrate that MMT may be a useful form of exercise training to improve balance in older adults. Although the underlying mechanism explaining the favorable effects of MMT in this study are not clear, it is possible that the power training component of this exercise program may play an important role in our outcomes, as alluded to by Tschopp et al.31 Consistent with our study, Theodorakopoulos et al32 also reported significant muscle strength improvements in older adults who had participated in circuit resistance training. Improvements in balance as a result of exercise training have also been attributed to increased lower-extremity muscle strength.33

Nevertheless, positive effects of exercise training demonstrated in older adults may not entirely be related to gains in muscle strength. This assumption is supported by the results of Nagai et al,27 who found that trained older adults may demonstrate more effective coactivation of muscles for postural control than untrained older adults. Similarly, others have observed changes in muscle activity with blunted decreases in the reduction of force variability associated with constant isometric contractions.34

Perhaps of equal interest, when we analyzed the group vs condition interaction for the total COP area of displacement (Fig 4), we observed that during the eyes open condition there were no statistical between-group differences. By contrast, with closed eyes, untrained older adults demonstrated significantly increased area compared with their trained counterparts. These results suggest that loss of balance in untrained older adults may also be attributable to losses in either vestibular or proprioceptive function.

There is evidence suggesting that both proprioception and vestibular function deteriorate with aging.35, 36, 37 If loss of vestibular function is one of the reasons for greater body sway in untrained older adults, the opposite observation showing that these same individuals are able to preserve average velocity with eyes open is consistent with reports of Horak,38 which suggested that patients with bilateral loss of vestibular function can rely on vision to decrease variability in trunk sway when standing on unstable surfaces. Nevertheless, the untrained older adults in our study most likely did not exhibit vestibular dysfunction, at least not severely, as none reported common symptoms such as vertigo and dizziness.39

Accordingly, in line with previous reports suggesting that exercise training may lead to attenuated declines,40 maintenance,41,42 or reacquired proprioception function with age,4 these data suggest that differences in proprioception are responsible for differences in ability to maintain body balance between trained and untrained older adults. Although there is no clear understanding of mechanisms to explain how physical training can affect joint proprioception of older adults,35 training may cause morphological adaptations in muscle spindles.43 It is also possible that increased muscle strength due to training may cause an improvement in proprioception.40 Finally, physical activity might work to modify proprioception by modulating the mechanoreceptor gain and inducing plastic changes in the central nervous system.44,45,46

In conclusion, these data suggest that with 1 year of regular MMT, older adults demonstrate similar performance in postural stability tests compared with younger adults. However, untrained older adults demonstrated worse performance in a postural stability test compared to both trained older adults and young adults.

Funding Sources and Conflicts of Interest

This paper received financial support of Fapesp Processo # 2012/09400-9 to Osmar Pinto Neto. No conflicts of interest were reported for this study.

Contributorship Information

Concept development (provided idea for the research): O.P.N., A.M., W.P.

Design (planned the methods to generate the results): O.P.N.

Supervision (provided oversight, responsible for organization and implementation, writing of the manuscript): O.P.N.

Data collection/processing (responsible for experiments, patient management, organization, or reporting data): O.P.N., A.M., W.P.

Analysis/interpretation (responsible for statistical analysis, evaluation, and presentation of the results): O.P.N., A.M., W.P.

Literature search (performed the literature search): O.P.N., A.M., W.P.

Writing (responsible for writing a substantive part of the manuscript): O.P.N., A.M.

Critical review (revised manuscript for intellectual content, this does not relate to spelling and grammar checking): O.P.N., A.M., W.P.

Practical Applications.

  • •

    This was an original study on the effects of MMT, a training modality widespread by trademarked programs (eg, CrossFit), on the balance of older adults.

  • •

    Balance control was significantly different between the trained and untrained older adults.

  • •

    Total average speed measurements were different between both young adults and trained older adults compared to untrained older only in an eyes-closed condition.

Alt-text: Unlabelled box

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