Under ideal conditions the maximum depolarization observed was approximately 20% of the threshold stimulus.

The minimum amount of stimulus needed in order for a muscle to contract is called the threshold stimulus.

The threshold stimulus produces the fiber's maximum response.

The strength-duration time constant (chronaxie) and rheobase are parameters that describe the strength-duration curve-the curve that relates the intensity of a threshold stimulus to its duration.

On the other hand, a stimulus just strong enough to initiate the impulse ("threshold stimulus") results in an electrical and chemical effect which is regenerated all along the nerve fiber and does not fade out.

After the threshold stimulus is reached, protein receptors in the motor end plate detect the neurotransmitter and an impulse spreads over the sarcolemma and into the T-tubules, where it goes to the sarcoplasmic reticulum.

This equation suggests that a graph of threshold stimulus strength versus stimulus duration should show a decay toward zero as stimulus duration is increased, so the stimulus strength required to reach threshold is predicted to increase during more protracted stimulation.