Muscle Twitch Myogram
- Muscle twitch is the response of a motor unit to a single action potential.
- A myogram traces the three phases of a muscle twitch.
X-axis = "Time (milliseconds)."
Y-axis = "Percentage of Maximum Tension."
Intercept = zero, which is the point of motor neuron stimulation.
Three phases of a muscle twitch from time 0 outward:
- Latent period; depends on the distance from the motor neuron to the skeletal muscle fiber as well as the speed of transmission down the axon.
No change in muscle tension during latent period.
- Contraction period: tension rises steadily to reach maximum tension.
- Relaxation period; is typically longer than the contraction phase:
The tension decreases. Muscles typically shorten during the contraction phase, and re-lengthen during the relaxation phase.