Changes in EMG characteristics and metabolic energy cost during 90-min prolonged running

This study quantified the interaction of integrated electromyography (iEMG) obtained from the vastus lateralis and the metabolic energy cost of running (Cr), an index to assess running economy, during 90-min prolonged running. The iEMG during running was divided into eccentric (ECC) and concentric (CON) phases using a force platform and a knee-joint goniometer. The ratio of ECC to CON (ECC/CON ratio) significantly decreased during 90-min prolonged running in novice distance runners, which would be explained by an increase in muscle activity during the CON phase of running. The average Cr value significantly increased during 90-min prolonged running. The individual's Cr values significantly correlated with the ECC/CON ratio (r = −0.702, P < 0.05). These results suggest that changes in the ECC/CON ratio and Cr value during prolonged running are associated.