Behavioral and neural adaptations in response to five weeks of balance training in older adults: a randomized controlled trial

Abstract

BackgroundWhile the positive effect of balance training on age-related impairments in postural stability is well-documented, the neural correlates of such training adaptations in older adults remain poorly understood. This study therefore aimed to shed more light on neural adaptations in response to balance training in older adults.MethodsPostural stability as well as spinal reflex and cortical excitability was measured in older adults (65–80 years) before and after 5 weeks of balance training (n = 15) or habitual activity (n = 13). Postural stability was assessed during one- and two-legged quiet standing on a force plate (static task) and a free-swinging platform (dynamic task). The total sway path was calculated for all tasks. Additionally, the number of errors was counted for the one-legged tasks. To investigate changes in spinal reflex excitability, the H-reflex was assessed in the soleus muscle during quiet upright stance. Cortical excitability was assessed during an antero-posterior perturbation by conditioning the H-reflex with single-pulse transcranial magnetic stimulation.ResultsA significant training effect in favor of the training group was found for the number of errors conducted during one-legged standing (p = .050 for the static and p = .042 for the dynamic task) but not for the sway parameters in any task. In contrast, no significant effect was found for cortical excitability (p = 0.703). For spinal excitability, an effect of session (p < .001) as well as an interaction of session and group (p = .009) was found; however, these effects were mainly due to a reduced excitability in the control group.ConclusionsIn line with previous results, older adults’ postural stability was improved after balance training. However, these improvements were not accompanied by significant neural adaptations. Since almost identical studies in young adults found significant behavioral and neural adaptations after four weeks of training, we assume that age has an influence on the time course of such adaptations to balance training and/or the ability to transfer them from a trained to an untrained task.Electronic supplementary materialThe online version of this article (doi:10.1186/s12952-017-0076-1) contains supplementary material, which is available to authorized users.

Modulation of soleus muscle H-reflexes and ankle muscle co-contraction with surface compliance during unipedal balancing in young and older adults

“…Our results suggest that such improvements would involve changes in control of the lower leg muscles and findings of decreased H-reflex gains in young adults (Gruber et al 2007) are in line with this. For older adults, it is unclear what the mechanisms behind such improved balance could be, as we found no changes in H-reflexes and co-contraction with changing surface compliance, and also in long-term training, no changes in H-reflex gains were found in older adults (Ruffieux et al 2017). Future, long-term studies, in which H-reflexes and co-contraction along with other potential mechanisms of balance improvement are measured could elucidate the how training on compliant surfaces can improve balance control.…”

Peer Review #1 of "Agility-based exercise training compared to traditional strength and balance training in older adults: a pilot randomized trial (v0.1)"

“…In the past, balance training has been considered task-specific (Kummel, Kramer, Giboin, & Gruber, 2016) and protocols for improving balance are recommended to last 11 to 12 weeks with 90 to 120 minutes of balance training per week (Lesinski, Hortobagyi, Muehlbauer, Gollhofer, & Granacher, 2015a). Underpinning those results, a focused balance training did not result in relevant improvements in similar measures as used in our study after five weeks (Ruffieux, Mouthon, Keller, Walchli, & Taube, 2017). Therefore, the interventions at hand might have been too short and unspecific to elicit changes in balance performance.…”

Follow-up efficacy of physical exercise interventions on fall incidence and fall risk in healthy older adults: a systematic review and meta-analysis

“…However, the aforementioned meta-analyses [ 40 , 44 , 49 , 55 , 59 , 60 , 69 ] considered also studies in which the intervention time was part of the follow-up time (follow-up starts at intervention onset). From a physiological perspective, it can be expected that intervention benefits occur after a certain volume of training (number of sessions over time) [ 91 – 93 ] and might become functionally relevant (i.e., reduce falls) even later and, further, that biological responses progress over the time-course of intervention. Therefore, given that the period of intervention in this analysis may include a time when training effects have not (yet) become effective, and that this period might be a significant portion of the assessed overall follow-up time (e.g., in the present data set the average intervention time of 5.6 months would be almost one third of the overall follow-up time of 18.0 months), this might explain the lower observed effects on fall rate ratio and risk ratio reported in the previously published analyses compared with the current meta-analysis.…”