Intro to Exercise Physiology 101: How a muscle contracts*skip this part if you dislike science* To simplify things, there are two primary phases of a muscular contraction. The phase where one is voluntarily acting against gravity to cause the muscle to contract is called the concentric phase. This phase is exemplified during the process of standing up from a seated position or pushing the weight towards the ceiling during a chest press. The final phase, termed as the eccentric phase, occurs when the muscle is passively lengthening with gravity. An example of this phase is displayed within the process of sitting down from a standing position or lowering the weight in the chest press. I am about to turn up the science just a smidge, but have no fear, I will eventually explain it in a manner that anyone should be able to grasp. During the concentric phase, contractile proteins form a cross-bridge, which causes the muscle to shorten (contract). During the eccentric phase, the contractile proteins detach from each other and cause the muscle to lengthen. *start reading again here if you skipped the science part*
Why we should care about the eccentric phaseBut who cares, right? Wrong. We should care because the eccentric phase elicits the greatest muscle damage. In other words, it offers the greatest potential for gains in strength and muscle. This may be due to the fact that we are 20-50% stronger eccentrically than we are concentrically. For example, one may not be able to curl a 45 lb dumbbell, but one may be able to control the weight downward (obviously, the amount of weight one can utilize is dependent upon the individual, but you should catch my drift). The best way to portray a muscle contraction and the damage caused in the eccentric phase is by thinking of a Velcro strap. The concentric phase would be strapping the Velcro together (minimal noise symbolizing minimal muscle damage). The eccentric phase would be peeling the Velcro apart (increased noise symbolizing increased muscle damage). But that’s not the only reasons we should care. Putting greater emphasis on the eccentric phase may increase flexibility, may strengthen tendons/ligaments, and it forces you to really focus on the technique of a movement, which all together will reduce the likelihood of injury. Since the eccentric phase is where the greatest benefits reside, why not just entirely focus on that portion of the exercise? Research suggests that to optimize strength and muscle, both muscle actions must occur. But that should seem obvious, anyways.
How to put emphasis on eccentric contraction:1) Adjust the tempo. – Try spending 1 second in the concentric phase and 2-4 seconds in the eccentric phase of an exercise. You want to focus on the eccentric phase as much as possible. Ex: Regarding the leg extension machine, take 1 second to extend both legs to lift the weight stack and take 4 seconds to lower the weight. 2) 2/1 method. – Use two limbs to lift a weight and one limb to lower the weight. Ex: Regarding the leg extension machine, extend both legs to lift the weight stack and use just one leg to lower the weight. 3) Combine options 2 and 3. Ex: Regarding the leg extension machine, take 1 second to extend both legs to lift the weight stack and take 4 seconds with just one leg to lower the weight.
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Written by Alex Tran, Certified Personal Trainer at Elite Sports Club-Brookfield. Alex has a B.S. in Exercise Science from Carroll University and is a Certified Strength and Conditioning Specialist (CSCS) by the National Strength and Conditioning Association. He specializes in Powerlifting/Strength Training, Soccer-Specific Training, and Youth Sports Performance. Alex lives by the philosophy that those belonging to the field of Exercise Science have a responsibility to uphold with the certain persons in which they serve. Alex advocates a science-based approach and views it as his duty to educate those who seek help with their body, with the hopes of administering a positive, long-term impact on the rest of their lives one rep at a time.