9.3 Mechanics of Single-Fiber Contraction

Concentric Contraction

Muscle activity that involves shortening of muscle length

Contraction Time

Time between beginning of force development and peak twitch tension by the muscle

Eccentric Contraction

Muscle activity that is accompanied by lengthening of the muscle generally by an external load that exceeds muscle force

Fast-Twitch Fibers

Fibers that have very short contraction times

Fused Tetanus

Skeletal muscle activation in which action potential frequency is sufficiently high to cause a smooth, sustained, maximal strength contraction

Isometric Contraction

Contraction of muscle under conditions in which it develops tension but does not change length

Isotonic Contraction

Contraction of muscle under conditions in which load on the muscle remains constant but muscle changes length

Latent Period

Period lasting several milliseconds between action potential initiation in a muscle fiber and beginning of mechanical activity

Load

External force acting on muscle

Optimal Length (L0)

Sarcomere length at which muscle fiber develops maximal isometric tension

Slow-Twitch Fibers

Fibers that have longer contraction times

Summation

Increase in muscle tension or shortening in response to rapid, repetitive stimulation relative to single twitch

Tension

In muscle physiology, the force exerted by a contracting muscle on an object

Tetanus

Maintained mechanical response of muscle to high-frequency stimulation

Twitch

Mechanical response of muscle to single action potential

Unfused Tetanus

Stimulation of skeletal muscle at a low-to-moderate action potential frequency that results in oscillating, submaximal force