Chronic eccentric exercise: improvements in muscle strength can occur withlittle demand for oxygen

Eccentric contractions, the lengthening of muscle while producing force, ar e a common part of our everyday movements. This study presents a challenge to the accepted notion that eccentric work causes obligatory muscle injury while demonstrating that an increase in muscle strength, via eccentric work , can occur with little demand for oxygen. Nine healthy subjects, ages 18-3 4, were randomly placed in either an eccentric or a concentric training gro up. Both groups trained for 6 wk while progressively increasing training fr equency and duration. Significant gains in isometric leg strength were seen in the eccentrically trained subjects only. While training, the oxygen con sumption required to do the eccentric work was equal to or less than that r equired to do the concentric work. The results demonstrate that by progress ively increasing the eccentric work rate, significant isometric strength ga ins can be made without muscle injury and with minimal increase in metaboli c demand for oxygen. The potential clinical implications of Em eccentric tr aining program that uncouples skeletal muscle strength improvements from th e demand for oxygen are alluring.