The concentric phase of a muscle contraction occurs when the muscle is contracting and shortening under tension. An example of this is when we perform a bicep curl and the biceps muscle shortens to allow us to pull the weight up towards our chest.
The eccentric phase of a muscle contraction occurs when the muscle is lengthening under tension. An example of this is when we are lowering the weight from our chest back to the starting position during the bicep curl.
The majority of emphasis is often placed on the concentric part of the contraction and we fail to perform the eccentric part of the contraction effectively. A common example of this is when we perform the bicep curl and bring the weight up towards our chest and get a good contraction and then just drop the weight back down to the starting position neglecting the eccentric phase of the contraction completely.
Why should we focus on the eccentric contraction?
One of the advantages of eccentric contractions is that greater forces can be generated during the eccentric phase compared to the concentric phase (1) This means more weight can be lifted throughout the eccentric phase. In addition, eccentric contractions require less motor unit activation and consume less oxygen and energy for a given muscle force than concentric contractions (2). This is significant meaning that less effort is needed during the eccentric part of the contraction meaning high intensity can be sustained for longer durations during exercise leading to greater training adaptations.
Several other studies have also shown that subjects who performed eccentric dominated exercise vs concentric dominated exercise had greater gains in muscle mass (3).
A systematic review by Douglas et al 2017 found that greater overall strength increases can be achieved after eccentric training than concentric or traditional training (5). Notably one study looked at basketball players and found that those subjected to eccentric training for 6 weeks exhibited a significant improvement in jumping height of 8% while the performance of the players that performed traditional weight-lifting was unchanged (6).
Other promising studies show the benefit of eccentric training for those who are overweight or obese as it has been shown to vastly improve body composition by both building muscle mass and reducing fat mass (4).
Over the past number of years growing attention has also been placed on the use of eccentric training on reducing the likelihood of muscle and tendon injuries in athletes. Controlled eccentric exercises have been shown to decrease the risk of hamstring injury in professional soccer players (7) and of shoulder pain in volleyball players (8).
So how should I perform the eccentric phase?
The main thing to take away from this article is that the eccentric phase of the contraction is just as important if not more important than the concentric phase of the muscle contraction, so don’t neglect it. When performing any exercise during the eccentric phase focus on lengthening the muscle gradually and under control to provide the maximum benefits. If it helps focus on counting to around 4-6 seconds during this phase.
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