The underlying mechanisms of improved balance after one and ten sessions of balance training in older adults

Neuromuscular adaptations to perturbation-based balance training using treadmill belt accelerations do not transfer to an obstacle trip in older people: A cross-over randomised controlled trial

BACKGROUND

This study examined (i) adaptations in muscle activity following perturbation-based balance training (PBT) using treadmill belt-accelerations or PBT using walkway trips and (ii) whether adaptations during treadmill PBT transfer to a walkway trip.

METHODS

Thirty-eight older people (65+ years) undertook two PBT sessions, including 11 treadmill belt-accelerations and 11 walkway trips. Surface electromyography (EMG) was measured bilaterally on the rectus femoris (RF), tibialis anterior (TA), semitendinosus (ST) and gastrocnemius medial head (GM) during the first (T1) and eleventh (T11) perturbations. Adaptations (within-subjects - 1st vs 11th perturbations for treadmill and walkway PBT) and their transfer (between-subjects - 1st walkway trip after treadmill PBT vs 1st walkway trip with no prior training) effects were examined for the EMG parameters.

RESULTS

Treadmill PBT reduced post-perturbation peak muscle activation magnitude (left RF, TA, ST, right RF, ST, GM), onset latency (right TA), time to peak (right RF) and co-contraction index (knee muscles) (P < 0.05). Walkway PBT reduced post-trip onset latencies (right TA, ST), peak magnitude (left ST, right GM), time to peak (right RF, ST) and pre-perturbation muscle activity (right TA) (P < 0.05). Those who undertook treadmill PBT were not different to those without prior training during the first walkway trip (P > 0.05).

CONCLUSIONS

Both treadmill and walkway PBT induced earlier initiation and peak activation of right limb muscles responsible for the first recovery step. Treadmill PBT also reduced co-contraction of the knee muscles. Adaptations in muscle activity following treadmill PBT did not transfer to a walkway trip.

Time-course of balance training-related changes on static and dynamic balance performance in healthy children

OBJECTIVE

In healthy children, there is evidence of improvements in static and dynamic balance performance following balance training. However, the time-course of balance training-related changes is unknown. Thus, we determined the effects of balance training after one, three, and six weeks of exercise on measures of static and dynamic balance in healthy children (N = 44, 20 females, mean age: 9.6 ± 0.5 years, age range: 9-11 years).

RESULTS

Participants in the intervention group (2 × 25 min balance exercises per week) compared to those in the control group (2 × 25 min track and field exercises and soccer practice per week) significantly improved their static (i.e., by measuring stance time in the One-Legged Stance test) and dynamic (i.e., by counting step number in the 3-m Beam Walking Backward test) balance performance. Late effects (after 6 weeks) occurred most frequently followed by mid-term effects (after 3 weeks) and then early effects (after 1 week). These findings imply that balance training is effective to improve static and dynamic measures of balance in healthy children, whereby the effectiveness increases with increasing training period.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN16518737 (retrospectively registered at 24th August, 2023).

Effects of balance training on cognitive function and activities of daily living in older adult patients with heart failure: a randomized controlled trial

BACKGROUND

The potential of the effect of balance training on improving cognitive functions and functional activities in vulnerable groups, including the older adults with heart failure (HF), is unknown.

AIM

The aim of the present study was to determine the effect of a simple balance training supervised by nurses on cognitive functions and activities of daily living (ADLs) of the older adults with HF.

METHODS

In this clinical trial study, 75 older adults with HF were allocated to two groups of balance training (BT) and usual care (UC) using stratified block randomization. The intervention consisted of a set of dynamic and static BT, 4 times/session per week, each session lasting 30 min, for 8 weeks, which was performed at the participant's home under the supervision of a nurse. For the control group, UC was provided. The outcomes of the study, including cognitive function, basic ADLs, and instrumental ADLs (IADLs), were measured by the Montreal cognitive assessment-basic (MoCA-B), Barthel index-ADL, and Lawton scale-IADL before and after the intervention.

RESULTS

The between-group analysis showed, in two groups, a statistically significant difference between the changes in the mean scores: all subscales of cognitive function and MoCA-B total score (P < 0.001), as well as basic ADLs and IADLs (P < 0.001), before and after the intervention. Compared with the control group/UC, the cognitive function, basic ADL, and IADL of the intervention group/BT were improved significantly at 8 weeks.

CONCLUSION

The results suggested that home-based balance training led by nurse can improve global cognitive function and basic ADL and IADL in the older adults with HF.

TRIAL REGISTRATION

Clinical trials registration number IRCT20150919024080N18.

Neural Correlates of Balance Skill Learning in Young and Older Individuals: A Systematic Review and Meta-analysis

BACKGROUND

Despite the increasing number of research studies examining the effects of age on the control of posture, the number of annual fall-related injuries and deaths continues to increase. A better understanding of how old age affects the neural mechanisms of postural control and how countermeasures such as balance training could improve the neural control of posture to reduce falls in older individuals is therefore necessary. The aim of this review is to determine the effects of age on the neural correlates of balance skill learning measured during static (standing) and dynamic (walking) balance tasks in healthy individuals.

METHODS

We determined the effects of acute (1-3 sessions) and chronic (> 3 sessions) balance skill training on balance in the trained and in untrained, transfer balance tasks through a systematic review and quantified these effects by robust variance estimation meta-analysis in combination with meta-regression. We systematically searched PubMed, Web of Science, and Cochrane databases. Balance performance and neural plasticity outcomes were extracted and included in the systematic synthesis and meta-analysis.

RESULTS

Forty-two studies (n = 622 young, n = 699 older individuals) were included in the systematic synthesis. Seventeen studies with 508 in-analysis participants were eligible for a meta-analysis. The overall analysis revealed that acute and chronic balance training had a large effect on the neural correlates of balance skill learning in the two age groups combined (g = 0.79, p < 0.01). Both age groups similarly improved balance skill performance in 1-3 training sessions and showed little further improvements with additional sessions. Improvements in balance performance mainly occurred in the trained and less so in the non-trained (i.e., transfer) balance tasks. The systematic synthesis and meta-analysis suggested little correspondence between improved balance skills and changes in spinal, cortical, and corticospinal excitability measures in the two age groups and between the time courses of changes in balance skills and neural correlates.

CONCLUSIONS

Balance skill learning and the accompanying neural adaptations occur rapidly and independently of age with little to no training dose-dependence or correspondence between behavioral and neural adaptations. Of the five types of neural correlates examined, changes in only spinal excitability seemed to differ between age groups. However, age or training dose in terms of duration did not moderate the effects of balance training on the changes in any of the neural correlates. The behavioral and neural mechanisms of strong task-specificity and the time course of skill retention remain unclear and require further studies in young and older individuals.

REGISTRATION

PROSPERO registration number: CRD42022349573.

Revisiting the use of Hoffmann reflex in motor control research on humans

Research in movement science aims at unravelling mechanisms and designing methods for restoring and maximizing human functional capacity, and many techniques provide access to neural adjustments (acute changes) or long-term adaptations (chronic changes) underlying changes in movement capabilities. First described by Paul Hoffmann over a century ago, when an electrical stimulus is applied to a peripheral nerve, this causes action potentials in afferent axons, primarily the Ia afferents of the muscle spindles, which recruit homonymous motor neurons, thereby causing an electromyographic response known as the Hoffmann (H) reflex. This technique is a valuable tool in the study of the neuromuscular function in humans and has provided relevant information in the neural control of movement. The large use of the H reflex in motor control research on humans relies in part to its relative simplicity. However, such simplicity masks subtleties that require rigorous experimental protocols and careful data interpretation. After highlighting basic properties and methodological aspects that should be considered for the correct use of the H-reflex technique, this brief narrative review discusses the purpose of the H reflex and emphasizes its use as a tool to assess the effectiveness of Ia afferents in discharging motor neurones. The review also aims to reconsider the link between H-reflex modulation and Ia presynaptic inhibition, the use of the H-reflex technique in motor control studies, and the effects of ageing. These aspects are summarized as recommendations for the use of the H reflex in motor control research on humans.

Effects of Motor-Cognitive Dual-Task Standing Balance Exergaming Training on Healthy Older Adults' Standing Balance and Walking Performance

Objective: This study examined the effects of motor-cognitive dual-task exergaming standing balance training on healthy older adults' static, dynamic, and walking balance. Methods: Twenty-four adults older than 70 years (control group: n = 9, males = 6, balance training group: n = 15, males = 8) completed the experiment. Dual-tasking standing balance training comprised the accurate control of a ping-pong ball on a tray held with both hands, while standing on one leg (analog training) and three modules of Wii Fit™ exergaming (digital training). The duration of balance training was ∼15 minutes per day, 2 days per week for 8 weeks, in total 16 sessions. We measured one-leg standing time, functional reach distance, walking balance evaluated by the distance walked on a narrow beam (4-cm long, 4-cm wide, and 2-cm high) with single and dual tasking, habitual and maximal walking speed, and muscle strength of the hip extensor, hip abductor, hip adductor, knee extensor, and plantarflexor muscle groups in the right leg at baseline and after 8 weeks. Results: Control group decreased, but balance training group increased one-leg standing time. Only the balance training group improved functional reach distance and hip and knee extensor strength. There was no change in walking speed and walking balance in either group. In the balance training group, changes in maximal speed correlated with changes in dual-tasking walking balance and changes in one-leg standing time correlated with changes in single-tasking walking balance. Conclusion: These results suggest that 16 sessions of motor-cognitive dual-task standing exergaming balance training substantially improved healthy older adults' static and dynamic balance and leg muscle strength but failed to improve walking speed and walking balance. Balance exercises specific to walking balance need to be included in balance training to improve walking balance.

Improvement in gait stability in older adults after ten sessions of standing balance training

Balance training aims to improve balance and transfer acquired skills to real-life tasks. How older adults adapt gait to different conditions, and whether these adaptations are altered by balance training, remains unclear. We hypothesized that reorganization of modular control of muscle activity is a mechanism underlying adaptation of gait to training and environmental constraints. We investigated the transfer of standing balance training, shown to enhance unipedal balance control, to gait and adaptations in neuromuscular control of gait between normal and narrow-base walking in twenty-two older adults (72.6 ± 4.2 years). At baseline, after one, and after ten training sessions, kinematics and EMG of normal and narrow-base treadmill walking were measured. Gait parameters and temporal activation profiles of five muscle synergies were compared between time-points and gait conditions. Effects of balance training and an interaction between training and gait condition on step width were found, but not on synergies. After ten training sessions step width decreased in narrow-base walking, while step width variability decreased in both conditions. Trunk center of mass displacement and velocity, and the local divergence exponent, were lower in narrow-base compared to normal walking. Activation duration in narrow-base compared to normal walking was shorter for synergies associated with dominant leg weight acceptance and non-dominant leg stance, and longer for the synergy associated with non-dominant heel-strike. Time of peak activation associated with dominant leg stance occurred earlier in narrow-base compared to normal walking, while it was delayed in synergies associated with heel-strikes and non-dominant leg stance. The adaptations of synergies to narrow-base walking may be interpreted as related to more cautious weight transfer to the new stance leg and enhanced control over center of mass movement in the stance phase. The improvement of gait stability due to standing balance training is promising for less mobile older adults.