Muscle contraction refers to the tension on the muscle that produces sufficient force to move an object (Anthony, 2018). When we move or exercise, we display various types of contraction, two of those being concentric and eccentric.
In concentric movement, muscles shorten as they contract, and in eccentric movement, they lengthen under load. Concentric contractions initiate movement or create an acceleration and eccentric contractions slow down or stop movement in order to protect the joint from muscle damage.
For over a decade, eccentric contraction has been a cornerstone of sports training and musculoskeletal chronic health management, which leads us to believe that eccentric contractions are much more efficient for rehabilitation (Hody, Croisier, Bury, Rogister, & Leprince, 2019 ). Let me explain you how it works.
During a concentric contraction, the tension in our muscles increases to meet a certain resistance, which makes us use more motor units, whereas during an eccentric contraction, our muscles lengthen due to an opposing force being greater than the force produced by our muscles, requiring fewer motor units. Eccentric contractions require less oxygen and energy to perform a similar exercise than concentric contractions. They produce force through both active and passive elements leading to higher force being developed. This results in faster hypertrophy, (Beardsley, 2018) which makes this type of contraction more efficient and metabolically less costly, causing less metabolite accumulation as the muscle fatigues. (Proske & Morgan, 2001).
Research by Hackney has shown that for both trained and untrained individuals, an exercise program that focuses on eccentric movement (1 sec concentric & 3 second eccentric) elevates the resting energy expenditure which is the rate at which you burn calories when the workout is over and you are resting (Aaron Bubbico & Len Kravitz, n.d).
Aaron Bubbico, B., & Len Kravitz, P. (n.d). Eccentric Exercie: A Comprehensive Review of a Distinctive Training Method. Retrieved from UNM EDU: https://www.unm.edu/~lkravitz/Article%20folder/eccentricUNM.html