Lower extremity joint moments during uphill cycling

Lower extremity joint moments were investigated in three cycling conditions : level seated, uphill seated and uphill standing. Based on a previous stud y (Caldwell, Li, McCole, & Hagberg, 1998), it was hypothesized that joint m oments in the uphill standing condition would be altered in both magnitude and pattern. Eight national caliber cyclists were filmed while riding their own bicycles mounted to a computerized ergometer. Applied forces were meas ured with an instrumented pedal, and inverse dynamics were used to calculat e joint moments. In the uphill seated condition the joint moments were simi lar in profile to the level seated but with a modest increase in magnitude. In the uphill standing condition the peak ankle plantarflexor moment was m uch larger and occurred later in the downstroke than in the seated conditio ns. The extensor knee moment that marked the first portion of the downstrok e for the seated trials was extended much further into the downstroke while standing, and the subsequent knee flexor moment period was of lower magnit ude and shorter duration. These moment changes in the standing condition ca n be explained by a combination of more forward hip and knee positions, inc reased magnitude of pedal force, and an altered pedal force vector directio n. The data support the notion of an altered contribution of both muscular and non-muscular sources to the applied pedal force. Muscle length estimate s and muscle activity data from an earlier study (Li & Caldwell, 1996) supp ort the unique roles of mono-articular muscles for energy generation and bi -articular muscles for balancing of adjacent joint moments in the control o f pedal force vector direction.