Characteristics of First Recovery Step Response following Unexpected Loss of Balance during Walking: A Dynamic Approach

Abstract

Introduction: Many falls in older adults occur during walking and result in lateral falls. The ability to perform a recovery step after balance perturbation determines whether a fall will occur. Aim: To investigate age-related changes in first recovery step kinematics and kinematic adaptations over a wide range of lateral perturbation magnitudes while walking. Methods: Thirty-five old (78.5 ± 5 years) and 19 young adults (26.0 ± 0.8 years) walked at their preferred walking speed on a treadmill. While walking, the subjects were exposed to announced right/left perturbations in different phases of the gait cycle that were gradually increased in order to trigger a recovery stepping response. The subjects were instructed to react naturally and try to avoid falling. Kinematic analysis was performed to analyze the first recovery step parameters (e.g., step initiation, swing duration, step length, and the estimated distance of the center of mass from the base of support [dBoS]). Results: Compared with younger adults, older adults displayed a significantly lower step threshold and at lower perturbation magnitudes during the experiment. Also, they showed slower compensatory step initiation, shorter step length, and dBoS with similar step recovery times. As the perturbation magnitudes increased, older adults showed very small, yet significant, decreases in the timing of the step response, and increased their step length. Younger adults did not show changes in the timing of stepping, with a tendency toward a significant increase in step length. Conclusions: First compensatory step performance is impaired in older adults. In terms of the dynamic approach, older adults were more flexible, i.e., less automatic, while younger adults displayed more automatic behavior.

Characteristics of step responses following varying magnitudes of unexpected lateral perturbations during standing among older people – a cross-sectional laboratory-based study

“…1 A'-D'), this supports the view that using the COS strategy was the best to control the moving CoM during the multiple-step trials at relatively high perturbation magnitudes, and that this response may not be under volitional control, thus, requiring an automatic response during the first recovery step. The present study results also indicate differences in balance recovery responses in walking [ 25 , 27 ] versus standing. Both Vlutters et al [ 25 ] and Nachmani et al [ 27 ] found that as the perturbation magnitudes increased during self-selected treadmill walking, there were small yet significant decreases in the timing of the step response.…”

“…The presence of single-step and multiple-step responses and the strategies of the first recovery step following a unannouced perturbations were verified offline using Windows Media Player (30 frames per-seconds), which allows video clip pauses, running the clip forwards and backwards, and slow motion. The following classifications were used [ 22 , 26 , 27 ]: Loaded-leg sideway stepping (LLSS)—the participant performs his/her initial step sideway with the loaded leg after the perturbation; Unloaded-leg sideway stepping (ULSS)–, the participant performshis/her initial step sideway with unloaded leg after the perturbation; Cross-over stepping (COS) the participant performed his/her stepping with the unloaded leg, while crossing the one leg over the other leg; Hip Abduction—the participant, abducted his/her hip joint of the unloaded leglateraly; Leg Collisions (Col). The unsuccessful balance recovery was defined as a fall into the safety harness system and grasping the harness system anchor straps or the research assistant to maintain their balance.…”

“…They found that foot placement after right/left perturbations was adjusted proportionally to the right/left CoM velocity, whereas forward/backward unexpected perturbations did not show a similar response. Nachmani et al [ 27 ] found that as the perturbation magnitudes increased during self-selected treadmill walking, older adults showed a small, yet significant decreases in the timing of the step response, and increased their step length…”

Muscle Activation Profile During Perturbed Walking is Modulated According to Body State

“…A larger sample might have provided greater statistical power to show more robust differences in the muscle activation patterns. Second, it is worth mentioning that perturbations were relatively weak and slow compared, for example, to (Handelzalts et al, 2019; Nachmani et al, 2020). This might have prolonged the recovery process.…”

Balance recovery stepping responses during walking were not affected by a concurrent cognitive task among older adults

“…In addition, older adults tend to respond with a recovery step at lower perturbation magnitudes [ 6 , 7 ] and tend to fall sideways which accounts for almost all hip fractures [ 1 ]. Compared to young adults, kinematic analyses of older adults’ recovery stepping responses during walking demonstrate slower recovery step initiation time, shorter step length, and larger safety margins of stability [ 8 ].…”