The three main muscle actions of the body include concentric, eccentric and isometric contractions. Concentric muscle actions involve force production as the muscle fibers shorten, as in the upward phase of the squat (knee and hip extension). Eccentric muscle actions involve force production as the muscle fibers lengthen, as in the downward phase of the squat (knee and hip flexion). Isometric muscle actions involve force production with unchanging muscle length, as in holding an abdominal contraction for an extended period of time during a forearm bridge, or with the lower body musculature in holding a three-point stance as a football lineman. Eccentric muscle actions are the most disruptive and damaging to muscle tissue while concentric contraction are less damaging. Some coaches prescribe exercises with emphasis on either the eccentric, concentric or isometric phase to elicit a specific training effect.
A new study published a head of print in the Journal of Applied Physiology, Nutrition and Metabolism, evaluated the effects of resistance training protocols emphasizing eccentric only or concentric only training on strength, hypertrophy and muscular endurance following a period of training and detraining. A group of 34 resistance trained males were randomly allocated to an eccentric, concentric or traditional (eccentric + concentric) control group. The training program centered around the bench press where training volume was equalized among the groups. Before and after the 6-week training program and again 6 weeks later (detraining), relative strength (1RM/body mass), maximum number of repetitions at a fixed load and chest circumference was measured.
The results showed that all three groups improved relative bench press strength similarly and significantly following the 6-week training period with no difference detected between training protocols. Following the 6-week detraining period, only the eccentric training group retained relative strength above pre-testing conditions while both concentric and traditional training groups returned to baseline values. In addition, only the eccentric training group improved and retained their muscular endurance by an average of +3 repetitions at a fixed load as well as being the only group to improve and maintain chest circumference (+2-3 cm). Therefore, to create lasting effects in strength, endurance and hypertrophy, coaches may want to consider eccentric training, particularly before extended breaks where the athletes may not be training.
Coratella, G., & Schena, F. (2016). Eccentric resistance training increases and retains maximal strength, muscle endurance and hypertrophy in trained men. Applied Physiology, Nutrition, and Metabolism, In Press.