Figure 3.

Disassociation between strength and age-associated differences in motor output variability during hand contractions. The top row demonstrates isometric strength (maximal voluntary contraction force, left panel), force trajectory variability (middle panel), and end-point variability (peak force, right panel) during a goal-directed isometric force task with the index finger in young (white bars) and older (black bars) adults (data adapted from (11)). The bottom row demonstrates maximal load that can be lifted (1-repetition maximum, left panel), movement trajectory variability (middle panel), and end-point variability (spatial variability, right panel) during a goal-directed movement in young and older adults with the index finger (data adapted from (10)). Overall, the findings suggest that, although young and older adults exert similar maximal capabilities with the index finger, older adults exert greater trajectory and end-point variability than young adults. This suggests that the amplified motor output variability in older adults is not associated with reductions in muscle strength.