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.

video anatomy muscles Skeletal muscle crash course crashcourse vlogbrothers PSK 4U sliding filament model motor units muscle twitches twitch summation tetanus isotonic movements isometric movements