Final answer:
An isometric contraction is a type of muscle contraction where the muscle increases in tension while its length remains unchanged, resulting in no movement of the body part despite muscle activation.
Step-by-step explanation:
The technique described in the question, where a client moves a body part without external assistance by voluntarily contracting the muscle, refers to an isometric contraction. During an isometric contraction, muscle tension increases but the length of the muscle itself remains the same. This means that while tension is created within the muscle, there is no joint movement or change in the angle of the body part. An example of this could be attempting to lift a stationary object that is too heavy to move. The contraction results in muscle activation and tension, but since the load is not overcome, the muscle does not shorten and the angle of the related joint stays the same.
Skeletal muscle is responsible for these voluntary, isometric contractions. It is referred to as voluntary striated muscle that is attached to the bones of the skeleton and helps the body move. Actions such as holding a yoga pose, maintaining proper posture, or stabilizing bones and joints typically involve isometric contractions of the skeletal muscle.