RELATIONSHIPS BETWEEN RUNNING ECONOMY AND TEMPORAL EMG CHARACTERISTICS OF BIARTICULAR LEG MUSCLES

Relationships between running economy (RE; submaximal VO2 for a given running speed) and the temporal EMG characteristics of bi-articular le g muscles were quantified in a group of well-trained runners. Nine sub jects completed three test sessions: a determination of maximal aerobi c demand (VO(2)max); an accommodation session at the experimental spee d of 4.13 m . s(-1); and a session during which EMG and RE data were c ollected simultaneously at the experimental speed of 4.13 m . s(-1). M easures of muscle onset, on-time durations, and on-time coactivation d urations were calculated from the following muscles: rectus femoris, m edial hamstrings, lateral hamstrings, and gastrocnemius. Nonparametric correlations between RE and EMG characteristics displayed both positi ve and negative relationships and exhibited a wide range of values. Tw o EMG measures were significantly correlated (r > 0.67) with RE. Earli er onset of rectus femoris during swing phase and a shorter duration o f hamstring - gastrocnemius coactivation during swing were associated with more economical runners, Although not statistically significant, correlation coefficients calculated for measures of coactivation durin g stance and RE ranged from -0.42 to -0.65. This trend indicates that individuals who exhibited a greater amount of coactivation between bi- articular muscles during the stance phase of the running cycle tended to be more economical, These relationships suggest different activatio n patterns in bi-articular muscles between economical and uneconomical runners.