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 affects the strength and duration of a contraction. This episode also explains twitch summation, tetanus, and isotonic vs. isometric movements.

Table of Contents
Skeletal Muscles Work Together to Create and Reverse Movements 1:14
Motor Units 3:52
Three Phases of Muscle Twitches 4:41
Strength and Frequency of Impulses 5:29
Strength and Duration of a Contraction 5:29
Twitch Summation vs Tetanus 6:19
Isotonic vs Isometric Movements 8:50

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View full lesson: https://ed.ted.com/lessons/what-makes-muscles-grow-jeffrey-siegel

We have over 600 muscles in our bodies that help bind us together, hold us up, and help us move. Your muscles also need your constant attention, because the way you treat them on a daily basis determines whether they will wither or grow. Jeffrey Siegel illustrates how a good mix of sleep, nutrition and exercise keep your muscles as big and strong as possible.

Lesson by Jeffrey Siegel, animation by Brett Underhill.