♠️FULL MOTOR UNIT RECRUITMENT♠️
🔹Recruiting all muscle fibers is one of the most important conditions that need to occur when striving to grow bigger muscles.
🔹Is it the only one? Definitely not, but it can be a prerequisite. In fact, if we can’t recruit high threshold muscle fibers, which are the fibers controlled by high threshold motor units, we won’t get any meaningful result from strength training, since they’re the ones which grow.
1️⃣ When lifting heavy weights, most motor units are quickly recruited and the weight is heavy enough to automatically cause high-threshold motor units to be recruited and actin-myosin bindings to form simultaneously.
🔹The same thing happens with moderate and light weights: as effort increases through each repetition, high threshold motor units are quickly recruited to make up for the lack of force exerted by low threshold muscle fibers.
🔹Bar speed is slow and because of the Force-Velocity relationship (which states that a slower shortening of the muscle fibers produces more force), the force output is greater, allowing the heavy weights to be moved.
2️⃣ Full motor unit recruitments occurs on high velocity movements too, however, because of the fact that the contraction is so fast or ‘explosive’ not enough tension is experienced by each fiber. This means no meaningful tension to cause muscle growth.
🔹So, while both movements show high levels of effort and full motor unit recruitment, only one will cause growth!
Resources:
2) https://medium.com/@SandCResearch/what-can-jumping-teach-us-about-muscle-growth-5bef1865246b
musclehacking.org 