Muscle Behavior  Threshold: the minimum voltage of electrical stimulus needed to achieve contraction  Twitch: a stimulus that causes a quick contraction and relaxation  Latent period: delay between stimulus and contraction (2msec)  Contraction phase: movement of load (rubber band)

Muscle Behavior  Relaxation phase: preparing for next twitch  Recruitment: bringing more motor units into play to increase contraction strength  Treppe: ride the wave of Ca+ as stimulus occurs before the tissue can reabsorb Ca+ from previous stimulus  Incomplete tetanus: muscle only relaxes partially between stimulus

Muscle Behavior  Complete tetanus: muscle has no time to relax, prolonged contraction to failure  Isometric contraction: contraction without a change in muscle length  Isotonic contraction: contraction with change in muscle length