What makes muscles grow Jeffrey Siegel
Muscles. We have over 600 of them. They make up between 13 and 12 of our body weight, and along with connective tissue, they bind us together, hold us up,and help us move. And whether or not body buildingis your hobby, muscles need your constant attention because the way you treat them on a daily basis
determines whether they will wither or grow. Say you're standing in front of a door,ready to pull it open. Your brain and muscles are perfectlypoised to help you achieve this goal. First, your brain sends a signalto motor neurons inside your arm. When they receive this message,they fire, causing muscles to contract and relax, which pull on the bones in your armand generate the needed movement. The bigger the challenge becomes,the bigger the brain's signal grows,
and the more motor units it ralliesto help you achieve your task. But what if the door is made of solid ironé At this point, your arm muscles alone won't be able to generate enough tension to pull it open, so your brain appeals to other muscles for help. You plant your feet, tighten your belly,and tense your back, generating enough force to yank it open. Your nervous system has just leveragedthe resources you already have,
other muscles, to meet the demand. While all this is happening, your muscle fibers undergo another kind of cellular change. As you expose them to stress,they experience microscopic damage, which, in this context, is a good thing. In response, the injured cells releaseinflammatory molecules called cytokines that activate the immune systemto repair the injury.
This is when the musclebuilding magic happens. The greater the damage to the muscle tissue, the more your body will need to repair itself. The resulting cycle of damage and repair eventually makes muscles bigger and stronger as they adapt to progressively greater demands. Since our bodies have already adaptedto most everyday activities, those generally don't produce enough stress
to stimulate new muscle growth. So, to build new muscle,a process called hypertrophy, our cells need to be exposed to higherworkloads than they are used to. In fact, if you don't continuously exposeyour muscles to some resistance, they will shrink, a process known as muscular atrophy. In contrast, exposing the muscleto a highdegree of tension, especially while the muscle is lengthening,