[Brandon is a student at the University of Mount Olive majoring in Exercise Science. He is currently an Athletic Development Intern at Athletic Lab.]
It appears now that eccentric training is thought to be most effective in reducing the risk of injury to athletes. In a study of hamstring strains it is stated that “biomechanical observations suggest that eccentric contraction is a necessary condition for a hamstring strain injury during running and this claim is strengthened by the lack of strain injuries in concentrically biased sports, such as swimming and cycling” (Opar, Williams, and shield, 2012). Eccentric training improves the amount of force that a muscle can absorb which makes it a clear benefit to preventing injuries in athletes. If you have heard of Cal Dietz method to tri-phasic training you will know that every muscle action has three phases: eccentric, isometric, and concentric. An eccentric action occurs when the “proximal and distal muscle attachments move away from one another” (Verkhoshansky & Siff, 2009). An isometric action occurs when the “proximal and distal muscle attachments do not move relative to each other” (Verkhoshansky & Siff, 2009). A concentric action occurs when the “proximal and distal muscle attachments move towards each other” (Verkhoshansky & Siff, 2009). Training a muscle through a full range of motion is typically the best way to see improvement throughout the entire muscle. This just makes sense because if you are using the entire muscle then the entire muscle will become stronger. However there may still be a need to focus on each phase of the muscle action during workouts. “Most muscle strains occur in an eccentric contraction and are affected by muscle strength and contraction velocity” (Liu, Garrett, Moorman, & Yu, 2012). If you could train a muscle to better handle the sudden stop of deceleration to acceleration would it decrease an athlete’s chances injury? I am led to believe that training the isometric phase of a muscle action plays just as much of a role in preparing muscles for potentially harmful forces as eccentric training. It should be understood that the undisputed best way to prepare any muscle for a movement is to perform the movement itself. However, all training programs need variability to balance specificity. Incorporating training sessions for isometric and eccentric strength will only aid in improving performance; possibly reducing muscle and tendon strains.
First, we need to understand how to effectively train isometric contractions such that it promotes the ability to stop a force quickly and then transfer that energy in the opposite direction quickly. A strong isometric contraction is “hugely important, because it acts as the springboard that launches the force from the stretch reflex and stretch-shortening cycle into the concentric contraction” (Peterson, 2012). The isometric phase of a muscle action has “two neurological processes that need to be trained to maximize the force transfer from the eccentric to concentric contractions” (Peterson, 2012). The number of muscle fibers recruited in the contraction needs to increase, as well as, the rate at which these fibers fire. By having a greater number of muscle fibers, that will react quicker, you will improve muscular tension throughout the isometric phase of a muscle action. You will also improve the rate at which energy is transferred into the concentric phase. When training to strengthen the isometric portion of a muscle action we should be able to quickly decelerate the weight eccentrically. Therefore, working at maximal loads is not the best way to train the isometric contraction. In this circumstance, athletes should not increase weight above 85% of their 1RM when training for isometric strength (Peterson, 2012). Quick deceleration in the weight room is going to help with quick deceleration on the field. Let’s say we are performing a squat. We will want to start by dropping the weight down at a fast pace and coming to a forceful stop. We will then hold the isometric contraction for 3-8 seconds depending on the weight. Following the pause is a rapid concentric contraction to fire the weight back up. “Explosive concentric contractions will train your nervous system” to aid in the transfer of energy from an eccentric and isometric contraction (Peterson, 2012). This is not to be confused with quasi-isometrics in which the overall movement is performed at a slow pace over time. We want to mimic the speed of a movement while putting emphasis on the isometric portion. This method of training is teaching your nervous system to create muscular contractions suddenly while under pressure. Granted the isometric portion of most movements is minuscule, utilizing isometric contractions in such a way that power is still an area of focus should translate in some way to the split second isometric contraction that occurs in all muscle actions.
Liu, H., Garret, W., Moorman, C., & Yu, B. (2012). Injury rate, mechanism, and risk factors of hamstring strain injuries in sports: a review of the literature. Journal of Sport and Health Science, 1(2).
Muscle Physiology Laboratory. (2008). Fundamental functional properties of skeletal muscle. Retrieved from http://muscle.ucsd.edu/
Opar, D. A., Williams, M. D., & Shield, A. J. (2012). Hamstring strain injuries. Sports Medicine, 42(3), 209-226.
Peterson, B. (2012). The importance of triphasic training, part 3: the isometric phase. Retrieved from http://www.stack.com/a/
Peterson, B. (2012). The importance of triphasic training, part 2: the eccentric phase. Retrieved from http://www.stack.com/a/
Rio, E. K. (2015). Isometrics reduce tendon pain. Retrieved from http://www.bodyinmind.org/
Verkhoshansky, Y., & Siff, M. (2009). Supertraining. Rome: Verkhoshansky