Résumé
The study's purpose was to determine the effect of foot orthoses on neuromuscular control and the aerobic cost of running.
Twelve recreational athletes ran for 1 h on a treadmill at a constant velocity (i.e., 10% higher than their first ventilatory threshold) with and without custom-molded foot orthoses, in a counterbalanced order. Surface EMG activity of five lower limb muscles, together with oxygen consumption and HR, was recorded at 8-min intervals, starting after 2 min, during the run. A series of neuromuscular tests including voluntary and electrically evoked contractions of the ankle plantar flexors was performed before and after running.
Peroneus longus root mean square amplitude decreased with time, independently of the condition (-18.9%, P < 0.01). Lower root mean square signal amplitude for vastus medialis (-13.3%, P < 0.02) and gastrocnemius medialis (-10.7%, P < 0.05), combined with increased peroneus longus burst duration (+14.7%, P < 0.05), occurred when running with orthoses. There was no main effect of the condition for oxygen consumption (P > 0.05), whereas HR was significantly lowered while wearing foot orthoses (-3%, P < 0.02). Maximal strength capacity (-9%, P < 0.01), normalized EMG activity (-17%, P < 0.001), and peak twitch torque (-14%, P < 0.01) declined from before to after exercise, independently of the condition. Smaller fatigue-induced decrements in the rate of torque development within the first 200 ms (-6% vs -33%, P < 0.01) were reported after running with foot orthoses.
Wearing foot orthoses alters neuromuscular control during a submaximal 1-h treadmill run and partly protects from the resulting fatigue-induced reductions in rapid force development characteristics of the plantar flexors. However, these changes may be too small to alter the aerobic cost of running.