# Abstract

 Physical exercise has been shown to improve cognitive functions. However, it is still unknown which type of exercise affects cognition. In the present study, we tested the hypothesis that a demanding balance training program improves memory and spatial cognition. Forty healthy participants aged 19--65 years were randomly assigned to either a balance or relaxation training intervention. Each group exercised twice a week for a total of 12 weeks. Pre- and posttests assessed balance performance, cardiorespiratory fitness, memory, spatial cognition, and executive functions. Only the balance group significantly increased in balance performance from pre- to posttest, while cardiorespiratory fitness remained unchanged in both groups. Moreover, the balance group significantly improved in memory and spatial cognition. Effects on executive functions were not observed. These results suggest that balance training is capable of improving particularly memory and spatial cognition. Therefore, an increase in cardiorespiratory fitness does not seem to be necessary to induce beneficial effects of physical exercise on cognition. It might be speculated that stimulating the vestibular system during balance training induces changes of the hippocampus and parietal cortex possibly via direct pathways between the vestibular system and these brain regions. # Results Participants of the balance and the relaxation group did not differ with respect to age, gender, vocabulary score, cardiorespiratory fitness, self-reported physical activity, and psychopathological symptoms (see Table [1](#)). Moreover, the groups did not differ significantly with respect to the physical and cognitive variables at pretest (all p > 0.250, see Table [2](#)). ::::table-wrap

::: caption
Physical and cognitive variables: Means (SD) at pre- and posttest
separately for the balance and the relaxation group.
:::

Test Time Balance group Relaxation group Adjusted group difference at posttest [95% CI], Cohens *d*

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Stability platform Pretest 5.40 (1.17) 5.73 (1.85) **1**.**57 \[0**.**49**, **2**.**65\]**, *d* = 0.66
Posttest 7.54 (2.57) 6.29 (1.84)\
BESS Pretest 15.24 (9.14) 17.78 (8.25) −0.52 [−0.3.25, 2.22], *d* = −0.09
Posttest 13.63 (8.68) 16.12 (7.38)\
CoP Pretest 0.55 (0.07) 0.59 (0.12) −0.001 [−0.08, 0.08], *d* = −0.01
Posttest 0.63 (0.11) 0.67 (0.18)\
VO~2~peak Pretest 31.83 (5.27) 30.883 (8.95) −0.83 [−3.49, 1.83], *d* = −0.14
Posttest 32.07 (6.52) 31.947 (7.89)\
Memory Pretest 7.50 (5.34) 7.67 (4.03) **1**.**60 \[0**.**05**, **3**.**05\]**, *d* = 0.47
Posttest 9.44 (5.48) 8.00 (4.16)\
Spatial Score Pretest 0.001 (0.80) −0.013 (0.77) **0.31 \[0**.**04**, **0.58\]**, *d* = 0.51
Posttest 0.443 (0.75) 0.040 (0.91)\
Stroop Pretest 229.88 (132.27) 255.59 (147.88) −3.47 [−66.39, 59.44], *d* = −0.03
Posttest 190.55 (81.87) 206.03 (120.41)\
Self-reported physical activity (hours/week) Pretest 8.03 (7.18) 7.25 (3.73) −1.12 [−4.62, 2.39], *d* = −0.17
Posttest 9.77 (6.61) 10.44 (6.89)\
Self-reported physical activity (MET/week) Pretest 29.28 (23.49) 27.72 (14.77) 1.37 [−12.03, 14.78], *d* = 0.05
Posttest 35.86 (24.27) 33.44 (24.43)\
GSI Pretest 0.59 (0.44) 0.49 (0.31) 2.68 [−2.95, 8.31], *d* = 0.16
Posttest 0.45 (0.33) 0.35 (0.22)

*Note*. Bold print differences denote significant results. GSI = Global
Severity Index of psychopathological symptoms. MET = Metabolic
equivalents, CoP = Center of pressure velocity.:::: 

## Physical Variables The balance training increased participants' dynamic balance performance on the stability platform as indicated by a significant effect of group, *F*(1, 36) = 8.72, *p* = 0.005. The mean of the balance training group at posttest was higher than the mean of the relaxation group (see Fig. [2](#), group difference = 1.57, 95% CI = [0.49, 2.65], *d* = 0.66). <figure> <p><img src="" /></p> <figcaption>Violin plots for the dynamic balance performance (stability platform) and cardiorespiratory fitness for the balance (dark gray) and the relaxation group (light gray) at pre- and posttest, showing the distribution and density of the data. Horizontal bars indicate the group mean. Error bars indicate 95% confidence intervals.</figcaption> </figure> There was no significant training effect on neither the CoP sway velocity as assessed with the forceplate, *F*(1, 36) \< 0.001, *p* = 0.962, group difference = −0.001, 95% CI = [−0.08, 0.08], *d* = −0.01, nor on functional balance, as measured with the BESS, *F*(1, 36) = 0.16, p = 0.704, group difference = −0.52, 95% CI = [−0.3.25, 2.22], *d* = −0.09. The training did not increase participants' cardiorespiratory fitness. There was no significant effect of group for VO~2~peak: *F*(1, 36) = 0.40, *p* = 0.531, group difference = −0.83, 95% CI = [−3.49, 1.83], *d* = −0.14, see Fig. [2](#). 

## Cognitive Variables A significant effect of group, *F*(1, 35) = 4.40, *p* = 0.043, was found for the memory score. After training, the adjusted mean of the balance group was higher than the mean of the relaxation group (group difference = 1.60, 95% CI = [0.05, 3.05], *d* = 0.47, see Fig. [3](#)). <figure> <p><img src="" /></p> <figcaption>Violin plots of the performance of the balance group (dark gray) and the relaxation group (light gray) for the memory test, spatial score and executive functions (Stroop test), showing the distribution and density of the data. Horizontal bars indicate the group mean. Error bars indicate 95% confidence intervals.</figcaption> </figure> The analysis of spatial score yielded a significant effect of group, *F*(1, 36) = 5.28, *p* = 0.027. After training, the adjusted spatial score was higher in the balance than in the relaxation training group (group difference = 0.31, 95% CI = [0.04, 0.58], *d* = 0.51, see Fig. [3](#)). To test whether the Stroop effect could reliably be elicited to measure executive functions in the present study, reaction times of congruent trials were compared to reaction times of incongruent trials, collapsed across groups and time. As expected, participants reacted faster in the congruent condition (M = 664.774 ms, SD = 177.583 ms) compared to the incongruent condition (M = 885.564, SD = 239.654 ms), *t*(134) = 6.37, *p* \< 0.001. To analyze training effects on executive functions, an interference score was calculated by subtracting the mean reaction time of the incongruent condition from the mean reaction time of the congruent condition for each participant. There was no significant effect of group on the Stroop interference score at posttest, *F*(1, 33) = 0.01, *p* = 0.911, group difference = −3.47, 95% CI = [−66.39, 59.44], *d* = −0.03 (see Fig. [3](#)). 

## Self-reported physical activity and psychopathological symptoms On average, participants increased their total weekly physical activity from M = 7.62 (SD = 5.58) hours at pretest to M = 10.12 (SD = 6.68) hours at posttest. Moreover, they expended more energy per week (MET score) at posttest (M = 34.59, SD = 24.07) than at pretest (M = 28.45, SD = 19.16). The average increase in self-reported physical activity reflects the participation in the supervised training, i.e. two hours/week with low to moderate intensity. Importantly, for the self-reported physical activity, the analysis yielded no significant effect of groups after training: Neither for hours/week: *F*(1, 36) = 0.42, *p* = 0.521, group difference = −1.12, 95% CI = [−4.62, 2.39], *d* = −0.17 nor for MET: *F*(1, 36) = 0.04, *p* = 0.84, group difference = 1.37, 95% CI = [−12.03, 14.78], *d* = 0.05, respectively (see Table [2](#)). The analysis of the psychopathological symptoms assessed with the SCL-90 displayed no significant effect of group, *F*(1, 37) = 0.42, *p* \< 0.521, group difference = 0.035, 95% CI = [−0.07, 0.14], *d* = 0.15, see Table [2](#)). Age did not correlate with changes from pre- to posttest in any of the physical and cognitive variables (all r \< 0.12, p > 0.250), indicating that younger and older participants did not differ in their benefits after training.


Extracted trial result:
Outcome: memory score (continuous)
Intervention: demanding balance training program
Comparator: relaxation group
Intervention mean: 9.44
Intervention standard deviation: 5.48
Comparator mean: 8
Comparator standard deviation: 4.16
Notes: Group sizes are in methods section only. Numerical values are from posttest.