Hank calls in a friend to do his push-ups for him today to explain how skeletal muscles work together to create and reverse movements. Hank and Claire also demonstrate the role size plays in motor units, the three-phase cycle of muscle twitches, and how the strength and frequency of an impulse affect the strength and duration of a contraction. This episode also explains twitch summation, tetanus, and isotonic vs. isometric movements.

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Chapters:
Introduction: Heavy Lifting 00:00
How Muscles Push & Pull 1:13
Functional Muscle Groups: Prime Movers, Antagonists, and Synergists 2:27
Motor Units 3:49
3 Phases of Muscle Twitches: Latent, Contraction, Relaxation 4:41
Graded Muscle Responses 5:22
Temporal Summation vs Tetanus 6:19
Multiple Motor Unit Summation (Recruitment) 7:07
The Size Principle of Recruitment 7:52
Isotonic vs Isometric Movements 8:50
Review 9:28
Credits 9:59


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