Shorter gastrocnemius lengths in older adults associate with worse capacity to enhance push-off intensity in walking

We posit that an age-related shift toward shorter plantarflexor operating lengths functionally limits force generation, and thereby the ability of those muscles to respond to increased propulsive demands during walking. In older subjects, we found a strong and significant positive correlation between gastrocnemius fascicle length at peak ankle moment during normal walking and performance on a ramped impeding force walking condition designed to increase the propulsive demands to their maximum, even after controlling for isometric strength. Our findings allude to age-related changes in plantarflexor muscle operating behaviour during walking that may be important for gait performance in older adults.