The Japanese have just conducted a clinical trial to check on the effect of eccentric movements. For those of you who aren’t up to speed on eccentric movement, in simple terms it is the force your muscles exert to resist a downward movement. In other words, if you were holding a weight above your head or pick up a really heavy object off a shelf, the muscles process involved in lowering the object is referred to as eccentric movement.
Bodybuilders have known for years the benefits reaped from exercising using eccentric motion. While your bicep might not be able to curl a specific weight, it can resist the downward movement of the dumbbell or barbell from the top position, in other words, lowering the weight. It is an excellent way to overload the muscle and bodybuilders refer to this movement as negative reps.
Typically, a person would assist you to lift the weight and you then do your utmost to resist the downward movement of the weight, fighting gravity. The result is an absolutely exhausted muscle and eccentric movements stimulate muscle growth. Bodybuilders have know this for decades. It is a go-to exercise to eke out more growth.
Science is only now starting to catch up. In a study, published in the European Journal of Applied Physiology , researchers divided people into three groups of 14 for a 5-week, twice-weekly comparison. In the group that both lifted and lowered weights, their was an increase in the maximum force they could produce on a lift by 18%, and the thickness of the biceps muscle increased by 11%.
The people who only lowered the weights nearly matched that, increasing their maximum force by 14% and muscle size by 10%. The lifting-only group increased their max force by 11%, while muscle size increase was insignificant.
Now while you might question the results and say that clearly the group who performed both the concentric (up) and eccentric (down) movement gained more, keep in mind that the group who only performed one range of motion (the eccentric) did basically half the work, showing results that were only minimally less than their peers who performed a full range of motion. So the question then is, why do concentric movements stimulate growth to the extent they do?
The author of the study, Masatoshi Nakamura, PhD, a professor at Nishikyushu University in Japan, suggests that eccentric muscle movements produce greater neurological adaptations in the spine and brain than concentric contractions. Simply put, your nerves adapt to send increased “pull harder” signals to your muscles. A large protein called “titin” in the muscle fibers produces greater force during eccentric contractions while using less energy, and more titin could account for the increase in muscle size, commonly referred to as hypertrophy. According to Nakamura;
“Titin in the muscle fibers could be the best explanation for muscle hypertrophy, However, we believe that other factors, such as neurological adaptations, also play a large role in increasing muscle strength.”
Whatever the biological reason for the efficacy of eccentric contraction, as science plays catchup to the world of sports, bodybuilders use a simple logic to justify the movement. Stressing the muscle beyond its capabilities stimulates growth. Our bodies are amazing machines and respond according to the stress placed on them.