Changes in electromyographic parameters during cycling exercise at constant intensity
Keywords: neuromuscular fatigue, cycling exercise
AbstractThe aim of this study was to evaluate the changes in surface electromyography (sEMG) parameters during 30-minute cycling exercise (250 W) at constant intensity in laboratory conditions. Ten male cyclists with the mean (±SE) age of 23.8±3.7 years participated. The sEMG power spectrum median frequency (MF) of rectus femoris, vastus lateralis, biceps femoris and erector spinae muscles, heart rate and the subjective rate of fatigue by Borg scale were measured in the beginning, during and at the end of exercise. Maximal voluntary contraction (MVC) force of the knee extensor muscles was assessed before and after the end of exercise. A significant decrease (p<0.05) in sEMG power spectrum MF for erector spinae muscle at the end of exercise compared to the initial level was found, whereas the knee extensor and flexor muscles revealed no significant changes in this parameter. The subjective rate of fatigue increased moderately during the cycling exercise (p < 0.05). The heart rate was stable during the exercise, remaining predominantly in the aerobic zone. After the exercise, MVC force was significantly (p<0.05) decreased compared to the pre-exercise level.
We concluded that based on sEMG power spectrum MF, 30-minute cycling exercise at constant intensity caused a marked fatigue of erector spinae muscle with no significant fatigue-induced changes in knee extensor and flexor muscles. A marked decrease of voluntary force capacity of knee extensor muscles was found after exercise. A moderate subjectively assessed fatigue was established at the end of exercise.