Effect of incline on lower extremity muscle activity during sprinting

Abstract

This study aimed to investigate the effect of incline on neuromuscular mechanisms in uphill sprint running. Nine male college sprinters performed 5-sec constant speed running trials on a motorized treadmill at 7.5 m/s. Each trial was conducted under different inclined conditions (level and 5.0% grade). Surface electromyography (EMG) was recorded from 6 muscles of the lower limbs, including gluteus maximus, gluteus medius, rectus femoris, vastus lateralis, biceps femoris, and lateral gastrocnemius lateralis. We found higher muscle activity in all muscles during the stance phase in uphill sprinting except for rectus femoris and vastus lateralis. Higher muscle activation during the recovery phase was found in the rectus femoris muscle in uphill sprinting. These muscle activity adaptations in uphill sprinting were paralleled by higher step frequency and shorter step length. Our results suggest that lower limb muscle activity can meaningfully adapt to sprint-specific demand in uphill running.