The Effect of Body Orientation on EMG Patterns in Cycling

Abstract

In human powered vehicles, manipulation of body orientation often results in changes in cycling performance. These changes in performance may be attributed to alterations in: (1) the aerodynamic properties of the cyclist and vehicle; (2) contribution of the lower limb weight to pedal force production; and/or (3) body configuration (joint angle changes affecting the interactions between the muscle length and moment arm length of the muscle groups involved in cycling). In a previous investigation examining cycling performance in a semi-prone, upright, and semi-recumbent position (the trunk relative to the ground at an angle of 60, 90, and 120 degrees, respectively), it had been concluded that an optimal cycling body orientation exists which maximizes power production (Too, 1991). Because the body configuration (hip, knee, and ankle angle) had been controlled for in that investigation, it had been speculated that differences in power production were attributed to changes in lower limb weight contribution to the total force on the pedals. It is believed that these differences would be reflected by changes in the muscle activity patterns. Therefore, it was the purpose of this investigation to determine whether cycling performance differences with different body orientations are attributed to changes in EMG patterns, as determined by one or more of these: (1) the sequence of activity by the different muscles; (2) the duration of the muscle activity; and (3) the pedal position each muscle was active and inactive during a complete pedal cycle.