The results suggest that young participants took more time than older to adjust the anticipatory biomechanical response to perturbation attempting to preserve balance during stepping.
Interestingly, young participants showed greater correlations between preparatory phase parameters and dynamic stability of the first step than older participants (average r of − 0.40 and − 0.06, respectively). Older participants responded to perturbation with lower increase in both magnitude ( p < 0.001 η 2 p = 0.62) and duration ( p = 0.001 η 2 p = 0.39) of preparatory parameters and soleus muscle activity ( p < 0.001 η 2 p = 0.55), causing shorter ( p < 0.001 η 2 p = 0.59) and lower ( p < 0.001 η 2 p = 0.43) stepping, compared to young participants.
Activation patterns of lower leg muscles were determined by surface electromyography. A stereophotogrammetric system and three force platforms were used to quantify mechanical parameters from the preparatory phase (e.g., timing and amplitude of postural adjustments) and from the stepping phase (e.g., step characteristics and dynamic stability). Ten young and ten older participants performed 10 gait initiation trials followed by 48 unperturbed and 12 perturbed trials in a random order. This study aimed to compare young and older individuals’ ability to generate postural responses and preserve stability in response to external waist perturbations delivered within gait initiation. An age-related decline in anticipatory postural mechanisms has been reported during gait initiation however, it is unclear whether such decline may jeopardize whole-body stability following unexpected balance perturbations.
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