Do Foot Orthoses Alter Muscle Activation, Running Economy and Neuromuscular Fatigue During a 1-h Treadmill Run?

Abstract

Foot orthoses are widely used in sports medicine for treatment, management and prevention of run-based lower limb injuries. It has been speculated that alterations in leg muscle activity with foot orthoses use may improve performance by reducing the extent of neuromuscular fatigue and consequently improving running economy. As yet this theory remains unproven. PURPOSE: To determine the effect of foot orthoses on muscle activation, running economy and neuromuscular fatigue during running. METHODS: Twelve recreational athletes (31.2 +/- 3.8 yr; 76 +/- 3.9 kg; 180.8 +/- 4.4cm) ran for 1 hour on a treadmill at a constant velocity (i.e. 10% higher than their first ventilatory threshold) with (Intervention, INT) and without (Control, CON) custom-molded orthotics in a counterbalanced order. Surface EMG of tibialis anterior (TA), soleus (SO), gastrocnemius medialis (GM), peroneus longus (PL) and vastus medialis (VM) muscles, together with, heart rate and oxygen consumption were recorded at 8 min intervals during the run. A series of neuromuscular tests including voluntary and electrically evoked contractions were performed before and after running. RESULTS: RMS activity for VM (-13.3% P<0.02,) and GM (-10.7%, P<0.05) was lower in INT compared to CON. Longer burst duration for PL (+14.7%; P<0.05) was recorded in the INT condition. PL RMS activity decreased with time, independently of the condition (-18.9%; P<0.01). There was no main condition effect for oxygen consumption (P>0.05), while heart rate was significantly lowered during INT (MD -3%; P<0.02). Oxygen consumption and heart rate (both P<0.05) increased with running duration. Maximal strength capacity (-9%; P < 0.01)), normalized EMG activity (-17%; P < 0.001) and peak twitch torque (-14%; P < 0.01) declined from pre- to post-tests, independently of the condition. Fatigue-induced decrements in the rate of torque development within the first 200 ms were larger in CON compared to INT (-33% vs. 6%; P<0.01). CONCLUSION: Wearing foot orthoses alters neuromuscular control and partly protects from fatigue-induced reductions in rapid force development characteristics in plantar flexors, in response to a sub-maximal 1-h treadmill run. Within the current study these changes may have been too small to manifest as improvements in running economy.