Both eccentric and concentric actions occur in conventional resistance exercise, but each has slightly different effects. Both can help you achieve increases in strength and muscle mass while burning fat. Focusing on one type of training may help you achieve specific goals. Consult a health-care professional before beginning any resistance-training program.
Eccentric and Concentric
Eccentric, or the lengthening phase, occurs when the muscles stretch to accommodate resistance. An example of this would be lowering the bar when performing the bench press. The agonists, or prime movers in the lift, your chest, shoulders and triceps, are lengthening as the bar comes down. This is sometimes called the negative portion of a repetition. The concentric, or shortening phase is when the agonists contract to perform a lift, such as your chest, shoulders and triceps contracting to push the barbell up when bench pressing. This is sometimes referred to as the positive portion of the repetition.
Eccentric training allows you to use more weight, as it is easier to lower weight that it is to lift it. This can allow for greater increases in microtrauma to your muscle fibers, which, assuming your rest time and diet is sufficient, can produce greater increases in muscle growth. A study published in the European Journal of Applied Physiology in February 2008 showed that eccentric overload when training offers significant benefits when trying to build muscle. Eccentric training is harder to recover from, and a study published in the European Journal of Applied Physiology in September 2010 showed that frequent eccentric-based training made recovery difficult and compromised gains in strength.
Concentric training allows you to generate and apply force and is often used as the preferred method of training for sports that require a high force output. Heavy throwing events, such as the hammer, discus and shotput, require both strength and the ability to quickly generate force. By training the concentric phase of a lift explosively, your ability to generate peak force in less time improves. A combination of both heavy resistance and resistance training with lighter weights can be used to build strength and power during the concentric phase. On many exercises to build power, you should use far less than your limit weight, according to a study published in August 2005 in the Journal of Strength and Conditioning Research.
It is possible to perform both heavy eccentric movements and still generate concentric force when training. Modifying your training in this manner requires a competent spotter. To overload your eccentric phase on the bench press, perform repetitions under your own power until you can no longer press the weight to full lockout. Have your spotter help you continue to lift until you can no longer press the bar off your chest. At this point, you have achieved total positive failure. If you have any energy left, your spotter can help you lift the bar, and you can continue to lower it under control until you achieve negative failure. This type of training is fatiguing and should not be practiced regularly.