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  • Muscles.

  • We have over 600 of them.

  • They make up between 1/3 and 1/2 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 building is 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 perfectly poised to help you achieve this goal.

  • First, your brain sends a signal to 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 arm and generate the needed movement.

  • The bigger the challenge becomes, the bigger the brain's signal grows,

  • and the more motor units it rallies to help you achieve your task.

  • But what if the door is made of solid iron?

  • 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 leveraged the 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 release inflammatory molecules called cytokines

  • that activate the immune system to repair the injury.

  • This is when the muscle-building 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 adapted to 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 higher workloads than they are used to.

  • In fact, if you don't continuously expose your muscles to some resistance,

  • they will shrink,

  • a process known as muscular atrophy.

  • In contrast, exposing the muscle to a high-degree of tension,

  • especially while the muscle is lengthening,

  • also called an eccentric contraction,

  • generates effective conditions for new growth.

  • However, muscles rely on more than just activity to grow.

  • Without proper nutrition, hormones, and rest,

  • your body would never be able to repair damaged muscle fibers.

  • Protein in our diet preserves muscle mass

  • by providing the building blocks for new tissue in the form of amino acids.

  • Adequate protein intake, along with naturally occurring hormones,

  • like insulin-like growth factor and testosterone,

  • help shift the body into a state where tissue is repaired and grown.

  • This vital repair process mainly occurs when we're resting,

  • especially at night while sleeping.

  • Gender and age affect this repair mechanism,

  • which is why young men with more testosterone

  • have a leg up in the muscle building game.

  • Genetic factors also play a role in one's ability to grow muscle.

  • Some people have more robust immune reactions to muscle damage,

  • and are better able to repair and replace damaged muscle fibers,

  • increasing their muscle-building potential.

  • The body responds to the demands you place on it.

  • If you tear your muscles up, eat right, rest and repeat,

  • you'll create the conditions to make your muscles as big and strong as possible.

  • It is with muscles as it is with life:

  • Meaningful growth requires challenge and stress.


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B1 US TED-Ed muscle repair tissue body damage

【TED-Ed】What makes muscles grow? - Jeffrey Siegel

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    SylviaQQ posted on 2016/02/25
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