Final answer:
A forceful, sustained muscle contraction is called a tetanus or tetanic contraction, which is a continuous contraction that occurs until the muscle fatigues.
Step-by-step explanation:
A forceful, sustained muscle contraction is called a tetanus or tetanic contraction. This type of contraction occurs when the concentration of calcium ions in the sarcoplasm allows virtually all of the sarcomeres to form cross-bridges and shorten, enabling the contraction to continue uninterrupted until muscle fatigue sets in. During tetanus, the muscle does not relax between stimuli, resulting in a continuous, steady state of maximal strength contraction.
When it comes to skeletal muscle contractions, there are two main types: isotonic contractions, where the muscle length changes, and isometric contractions, where muscle length remains the same but muscle tension changes.
The level of muscle tension and the efficiency of muscle contractions can be influenced by various factors including the number of motor units recruited, the frequency of action potentials, and the length-tension relationship of the sarcomeres.