GLOSSARY

Rate coding is the mechanism by which the nervous system increases muscle force by increasing the number of action potentials per second in active motor units.

Mechanism

• Low frequency: each action potential produces a single twitch, and the muscle has time to relax.
• Higher frequency: contractions summate before relaxation is complete (temporal summation), and force rises.
• Very high frequency: contractions fully fuse to produce tetanus with maximal force.

Frequency Range

Typical motor unit firing rates in voluntary contraction are about 5–50 hertz