Effects of locomotor muscle fatigue on joint-specific power production during cycling

Previous authors have reported reductions in maximum power after high-intensity cycling exercise. Exercise-induced changes in power produced by ankle, knee, and hip joint actions (joint-specific powers), however, have not been reported.

Our purpose was to evaluate joint-specific power production during a cycling time trial (TT) and also to compare pre- to post-TT changes in maximal cycling (MAXcyc) joint-specific powers.

Ten cyclists performed MAXcyc trials (90 rpm) before and after a 10-min TT (288 ± 10 W, 90 rpm). Pedal forces and limb kinematics were determined with a force-sensing pedal and an instrumented spatial linkage, respectively. Joint-specific powers were calculated and averaged over complete pedal cycles and over extension and flexion phases.

Pedal and joint-specific powers did not change during the TT. Compared to pre-TT, pedal power produced during post-TT MAXcyc was reduced by 32% ± 3% (P < 0.001). Relative changes in ankle plantarflexion (43% ± 5%) and knee flexion powers (52% ± 5%) were similar but were greater than changes in knee extension (12% ± 4%) and hip extension powers (28% ± 6%; both P < 0.05). Pedal and joint-specific powers produced during post-TT MAXcyc were greater than those powers produced during the final 3 s of the TT (P < 0.01).

Exercise-induced changes in MAXcyc power manifested with differential power loss at each joint action with ankle plantarflexion and knee flexion exhibiting relatively greater fatigue than knee extension and hip extension. However, changes in MAXcyc joint-specific powers were not presaged by changes in TT joint-specific powers. We conclude that fatigue induced via high-intensity cycling does not alter submaximal joint-specific powers but has distinct functional consequences for MAXcyc joint-specific powers.