Effects of cycling with the knees close to the bicycle frame on the lower limb muscle activation

Abstract

Cyclist's body position on the bike has been related to changes in muscle activation. Therefore, the aim of the present study was to compare the activation of Tibialis Anterior, Gastrocnemius Medialis, Biceps Femoris, Rectus Femoris, Vastus Lateralis, Adductor Longus e Gluteus Maximus muscles in three conditions: 1) reference position (preferred position); 2) adduction position (knees almost touching the bicycle frame); 3) abduction position (knees away from the bicycle frame). Six athletes with competitive experience in cycling were evaluated using surface electromyography. They pedalled using their own bicycles mounted on a wind-trainer, with a workload relative to the second ventilatory threshold. Muscle activation was defined by the mean value of the RMS envelope and by the activation period for the three evaluated positions. There were no significant differences in muscles' RMS or activation period between the three positions, except for the Adductor Longus muscle. In adduction position, this muscle was more activated (36 ± 6%), compared to the abduction position (25 ± 11%) for a significance level of p = 0.02, without significant differences for the reference position (27 ± 7%). These results indicate that there is no substantial difference in the activation of the most important muscles of the lower limb when the position of the knee is changed in the frontal plane for the same workload level, with the Adductor Longus as an exception.