Muscle contracts and shortens at constant rate of speed, usually requires special, expensive equipment that increases the load as it senses that the muscle contraction is speeding up. *

This given statement is about "Isotonic Contraction".

Explanation:

There are basically two types of muscle contraction named as Isotonic and Isometric contraction.The variations of length of muscles take place when muscular contraction is against resistance then termed as "Isotonic contractions".

This retains constant muscle tension, as the length of the muscle varies.This can only occur when the average contraction force of a muscle is greater than the total load on the muscle.

Isotonic movements are either intense, which means shortening the working muscle, or eccentric, which means lengthening the working muscle. Isometric contraction involving muscle contraction to stress, in which the muscle length stays the same.