What makes muscles grow? - Jeffrey Siegel

Hard words

The longest, least common words in this video. Say them slowly before you start.

• progressively
• continuously
• inflammatory
• testosterone
• contraction
• hypertrophy
• lengthening
• microscopic

Transcript: 35 sentences

Tap a sentence to start the drill right there.

1. 0:07 Muscles.
2. 0:08 We have over 600 of them.
3. 0:10 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.
4. 0:20 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.
5. 0:31 Say you're standing in front of a door, ready to pull it open.
6. 0:34 Your brain and muscles are perfectly poised to help you achieve this goal.
7. 0:39 First, your brain sends a signal to motor neurons inside your arm.
8. 0:43 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.
9. 0:53 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.
10. 1:01 But what if the door is made of solid iron?
11. 1:05 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.
12. 1:14 You plant your feet, tighten your belly, and tense your back, generating enough force to yank it open.
13. 1:20 Your nervous system has just leveraged the resources you already have, other muscles, to meet the demand.
14. 1:28 While all this is happening, your muscle fibers undergo another kind of cellular change.
15. 1:33 As you expose them to stress, they experience microscopic damage, which, in this context, is a good thing.
16. 1:40 In response, the injured cells release inflammatory molecules called cytokines that activate the immune system to repair the injury.
17. 1:50 This is when the muscle-building magic happens.
18. 1:54 The greater the damage to the muscle tissue, the more your body will need to repair itself.
19. 1:59 The resulting cycle of damage and repair eventually makes muscles bigger and stronger as they adapt to progressively greater demands.
20. 2:08 Since our bodies have already adapted to most everyday activities, those generally don't produce enough stress to stimulate new muscle growth.
21. 2:17 So, to build new muscle, a process called hypertrophy, our cells need to be exposed to higher workloads than they are used to.
22. 2:25 In fact, if you don't continuously expose your muscles to some resistance, they will shrink, a process known as muscular atrophy.
23. 2:34 In contrast, exposing the muscle to a high-degree of tension, especially while the muscle is lengthening, also called an eccentric contraction,
24. 2:43 generates effective conditions for new growth.
25. 2:47 However, muscles rely on more than just activity to grow.
26. 2:50 Without proper nutrition, hormones, and rest, your body would never be able to repair damaged muscle fibers.
27. 2:57 Protein in our diet preserves muscle mass by providing the building blocks for new tissue in the form of amino acids.
28. 3:04 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.
29. 3:16 This vital repair process mainly occurs when we're resting, especially at night while sleeping.
30. 3:22 Gender and age affect this repair mechanism, which is why young men with more testosterone have a leg up in the muscle building game.
31. 3:30 Genetic factors also play a role in one's ability to grow muscle.
32. 3:35 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.
33. 3:45 The body responds to the demands you place on it.
34. 3:48 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.
35. 3:57 It is with muscles as it is with life: Meaningful growth requires challenge and stress.

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