Rectus femoris activation is modified by training status and correlates with endurance performance in cycling

The study aimed to compare the activity of low and fast-twitch muscle fibers of the prime mover muscles used in cycling between recreational cyclists with different training levels during a high-intensity exercise. Twelve male cyclists performed, on distinct days, a graded exercise test and two bouts of cycling at severe-intensity. The first bout was performed as familiarization and the second to monitor the muscle activation through surface electromyography (EMG) of the rectus femoris, vastus lateralis, biceps femoris, and gluteus maximus. According to peak oxygen uptake (V̇O_2peak) and maximal aerobic power (MAP), participants were classified as untrained ( V̇O_2peak = 43.5 ± 1.2 mL kg −1 min −1 , MAP = 3.3 ± 0.1 W kg −1 ) or recreationally trained ( V̇O_2peak = 53.7 ± 2.9 mL kg −1 min −1 , MAP = 4.4 ± 0.4 W kg −1 ). During high-intensity exercise, the recreationally trained group presented higher area under the root mean square curve ( p = 0.013, statistical power = 77