Concentric Versus Eccentric Muscular Action
It is vital to understand and train the different muscular actions. In athletics, it is the job of the strength and conditioning coach to take into account not only when specific muscular actions occur but also from which muscles. This knowledge allows the strength coach to create a program that achieves greater levels of athletic performance. Resistance training that utilizes the three muscular actions invokes superior adaptations that lead to athletic performance; a leaner and sexier physique; greater levels of fitness; and overall health.
The three types of muscular actions are eccentric, concentric and isometric. Only concentric and eccentric are dynamic muscular actions. These two actions are considered dynamic because the muscle-length tension relationship changes while force is being applied upon them (1). During training, the majority of resistance exercises and apparatuses are developed to allow lifters to perform both the eccentric and concentric muscular actions in sequence. There is a strong correlation between this style of training and fitness / athletic performance enhancement because real life movements require both actions sequentially.
Eccentric muscular actions are when the external weight forces itself upon skeletal muscle and the muscle fibers lengthen during contraction to handle the load. The muscles decelerate or control the force that is being applied upon the body. For example, the downward motion of squat is an eccentric muscular action. The NSCA states that elevated levels of mechanical stress results in higher amounts of muscular stimulation / growth (1). The eccentric action is required to generate muscular growth during resistance training, which leads to strength, power, speed, quickness, reduced injury, fat loss and a lean physique.
The eccentric action comes with inherent risks as well. The eccentric motion has the highest injury risk out of the three muscular actions. In fact, the majority of non-contact injuries in athletics occur during rotation and eccentric muscular actions because it generates the greatest amount of mechanical stress. Other less favorable side effects of eccentric training are muscular soreness, fatigue and inflammation. These side effects can be avoided if concentric muscular action training is solely performed. However, neglecting the eccentric action is not favorable because it will result in limited muscular growth and injury prevention.
Concentric muscular actions are when skeletal muscles apply force upon an external object or move our body; as a result, the muscle fibers shorten during the contraction. For example, standing up from a squat is a concentric muscular action. Concentric muscular actions propel athletes during sprinting, jumping, hitting, etc… In swimming, concentric muscular actions are the only actions utilized because gravity is a non-factor while in the water; therefore, it is imperative to utilize and develop a higher force capability / output. Movements such as clean pulls, bottom bench, heavy ropes, box jumps and/or snatch pulls emphasize the concentric muscular action and can be advantageous to minimize soreness while training fast twitch fibers. However, the majority of sports require athletes to utilize a muscular / tendon pre-stretch, better known as “the stretch shortening cycle,” which involves a sequential eccentric-concentric muscular action.
Although eccentric actions lead to the greatest amounts of muscular adaptations / growth, concentric focused training has shown favorable results. One study found that after 8 weeks of concentric-isokinetic resistance training participant’s strength and size increased (2). This study, along with other research, supports concentric focused training as a way to increase muscular strength, size and performance. The added benefit of concentric focused training is a decrease in muscular fatigue and soreness.
Concentric based training may be favorable during in-season training or weeks leading up to competitions. The lack of soreness and fatigue allows athletes and persons alike to maintain their sport specific training without losing muscular adaptations. However, in order to achieve the greatest amount of sport and/or fitness performance persons should continue to engage in eccentric, isometric and concentric based training. There are very few movements, if any at all, that do not require each of the three actions.
Here are a few lower body movements that lead to reduced injury and muscular growth while engaging in all three muscular actions:
-Squats (back, front and split) that engage in a full range of motion (ROM). Full ROM squats require proper technique and progression but result in increased speed, vertical jumping, muscle growth and injury prevention.
-Single Leg Squats are movements that require lifters to squat down on one leg; be sure to limit the amount of forward lean so that the knee only slightly passes in front of the toes near parallel or below.
Here are a few concentric focused movements that can increase power output with less soreness, loss of repeated strength and muscular fatigue:
-Heavy Rope training is concentric only; a force must be imposed upon ropes, through concentric muscular action, to move them. To view heavy rope exercises please visit www.functionalmusclefitness.com.
-Clean or Snatch Pulls are Olympic lifting movements that require the athlete to explosively pull the barbell from the ground until it is past the lifters mid-section; the exercise requires coordination and total body strength, not to mention much more complicated than how I described it. Upon completion of the pull the lifter allows the barbell to fall to the floor. This movement should be used with Olympic lifting plates and/or bumpers. Athletes must have the flexibility to squat down without a rounded back to perform this movement; therefore, make sure the athlete knows how to deadlift first.
Athletes please note that concentric style training is a great way to train leading up to a competition. During the last weeks leading into competition soreness is not warranted. Seek out an educated strength and conditioning coach that understands in-season training. Your goal should be to emphasize concentric action lifts to maintain, even slightly increase, strength and power. However, it is always vital to continue to perform eccentric movements to ensure optimal performance, health and longevity.
1. The Essentials of Strength Training and Conditioning (3rd edition).
By, National Strength and Conditioning Association
Editors: Thomas R. Baechle and Roger W. Earle
©2008, 2000, 1994
2. Effects of unilateral concentric-only dynamic constant external resistance training on quadriceps femoris cross-sectional area.
Housh DJ, Housh TJ, Weir JP, Weir LL, Evetovich TK, and Donlin PE.
Journal of Strength and Conditioning 12: 185-191, 1998
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