Exercise of Dynamic Stability in the Presence of Perturbations Elicit Fast Improvements of Simulated Fall Recovery and Strength in Older Adults: A Randomized Controlled Trial

Abstract

Age-related impairments of reactive motor responses to postural threats and reduced muscular capacities of the legs are key factors for the higher risk of falling in older people. It has been evidenced that a training of dynamic stability in the presence of perturbations has the potential to improve these deficits. However, the time course of training effects during such interventions is poorly understood. The purpose of this parallel-group study was to investigate the temporal adaptation dynamics of the balance recovery performance and leg strength during a dynamic stability training. Forty-two healthy older adults (65-85 years) were randomly assigned to a training (n = 27, analyzed n = 18) or control group (n = 15, n = 14). The training was conducted in a group setting for 6 weeks (3×/week, 45 min). The exercises focused on the mechanism of stability control (i.e., modulation of the base of support and segment counter-rotations around the center of mass) during standing, stepping, and jumping on unstable surfaces with a high balance intensity. Before, after 3 and after 6 weeks, the maximum plantar flexion moment and the knee extension moment were assessed. The recovery performance was evaluated by a simulated forward fall (lean-and-release test) and the margin of stability concept. The margin of stability at release decreased significantly after 3 weeks of training (34%, effect size g = 0.79), which indicates fast improvements of balance recovery performance. The margin of stability further decreased after week 6 (53%, g = 1.21), yet the difference between weeks 3 and 6 was not significant. Furthermore, the training led to significant increases in the plantar flexion moment after weeks 3 (12%, g = 0.72) and 6 (13%, g = 0.75) with no significant difference between weeks. For the knee extension moment, a significant increase was found only after week 6 (11%, g = 1.07). The control group did not show any significant changes. This study provides evidence that a challenging training of dynamic stability in the presence of perturbations can improve balance recovery performance and leg strength of older adults already after a few weeks. Therefore, short-term training interventions using this paradigm may be an effective strategy for fall prevention in the elderly population, particularly when intervention time is limited.

Keywords: aging; dynamic stability training; fall prevention; randomized controlled trial; reactive control; unexpected perturbations and disturbances.

Figure 1

Flow chart illustrating the progress of the intervention trial.

Figure 2

Description of the concept of the training of the dynamic stability in the presence of perturbations. Participants trained each of the exercise blocks under unstable conditions introduced by the different kinds of used equipment. The balance intensity was kept high by modifying the exercises according to the individual performance level to challenge the application of the dynamic control mechanisms (horizontal and vertical axis).

Figure 3

Changes of the margin of stability at release (ΔMoS_Release) during the simulated forward falls between weeks 0 and 3 as well as weeks 0 and 6 for the intervention (n = 18) and control groups (n = 14), respectively. Statistically significant main effect of + time and # group (p < 0.05). *Statistically significant difference (post-hoc analysis) to baseline, i.e., week 0 (p < 0.05).

Figure 4

Relationship between the exercise-induced change of the margin of stability at release (ΔMoS_Release) and the rate of the base of support increase (ΔRate BoS) from release to touchdown during the simulated forward fall for the time course of week 0 to week 3 (n = 16) and week 3 to week 6 (n = 14).