Functional relevance of eccentric strength maintenance with age during walking

Muscle strength declines with age. However, this reduction of strength in older age is two-fold less when muscles actively lengthen (i.e., eccentric contraction) as compared to when they shorten (i.e., concentric contraction) or remain at constant length (i.e., isometric contraction). Even though the relative maintenance of eccentric strength is a robust age-related phenomenon, it is unclear whether it has functional benefits for the execution of daily functional tasks. As lengthening muscle contractions are inherent to walking and humans mainly rely on lengthening contractions during descending gaits, this thesis examined the functional relevance of eccentric strength maintenance with age during walking in older adults. Specifically, we determined its functional relevance at the gross motor level (i.e., walking speed) and at the joint level (i.e., net joint mechanical outputs) during level and non-level walking. A key finding was that age-related differences in joint mechanical outputs during walking were attenuated during phases of eccentric force generation relative to phases of concentric force generation. This finding suggests that the maintenance of eccentric strength in old age is also apparent during an important activity of daily living, i.e., walking.