Relationships Between Running Economy and Temporal EMG Characteristics of Bi-Articular Leg Muscles

Relationships between running economy (RE; submaximal VO₂ for a given running speed) and the temporal EMC characteristics of bi-articular leg muscles were quantified in a group of well-trained runners. Nine subjects completed three test sessions: a determination of maximal aerobic demand (VO₂max); an accommodation session at the experimental speed of 4.13 m · s^-1; and a session during which EMC and RE data were collected simultaneously at the experimental speed of 4.13 m · s^-1 Measures of muscle onset, on-time durations, and on-time coactivation durations were calculated from the following muscles: rectus femoris, medial hamstrings, lateral hamstrings, and gastrocnemius. Nonparametric correlations between RE and EMC characteristics displayed both positive and negative relationships and exhibited a wide range of values. Two EMC measures were significantly correlated (r>0.67) with RE. Earlier onset of rectus femoris during swing phase and a shorter duration of hamstring - gastrocnemius reactivation during swing were associated with more economical runners. Although not statistically significant, correlation coefficients calculated for measures of coactivation during 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 activation patterns in bi-articular muscles between economical and uneconomical runners.

Key words

Aerobic demand - biomechanics - electromyography - muscle activity