Neuromuscular activation of the knee and hip extensor muscles during high-intensity interval and moderate-intensity...

We aimed to test the hypothesis that the magnitude of differences in muscle activation of the knee and hip extensor muscles between high-intensity interval exercise (HIE) and moderate-intensity constant exercise (CE) would be greater for the gluteus maximus than for the quadriceps femoris muscle. Participants were 11 male middle- or long-distance runners. The HIE (4 sets, 4-min induration, performed at 80-85%VO_2peak and followed by a 3-min period of cycling at < 30%VO_2peak) and CE (28-min, performed at or near 60%VO_2peak) were completed on different days, with the total exercise duration and work being identical for both protocols. Surface electromyography (EMG) was recorded from the following muscles: vastus lateralis, vastus medialis, rectus femoris, gluteus maximus, and biceps femoris. The EMG amplitude, normalised over a period of 28 min for both protocols, was significantly greater during HIE than during CE for the gluteus maximus (HIE: 43 ± 4% versus CE: 24 ± 7%) and rectus femoris (HIE: 62 ± 23% versus CE: 47 ± 18%), but had no effect of the exercise protocol on the EMG amplitude of other muscles. These findings indicate that the relative contribution of the gluteus maximus and rectus femoris to the cycling movement can be enhanced using a HIE protocol, in middle- and long-distance runners.