Final answer:
The correct answer is 'c,' as the force of a contraction remains constant during isometric contractions. Isotonic contractions involve changes in muscle length but constant muscle tension, and myofilaments slide during isotonic, not isometric contractions.
Step-by-step explanation:
The most accurate statement about muscle contractions is that the force of a contraction remains constant during an isometric contraction. This is because during isometric contractions, although the tension in the muscle increases, the muscle itself does not change length since the load cannot be moved. Therefore, statement 'c' is the most accurate.
Conversely, during an isotonic contraction, the tension within the muscle remains relatively constant while the length of the muscle changes. This implies that the muscle can move the load. There are two types of isotonic contractions: concentric, where the muscle shortens to move a load, and eccentric, where the muscle lengthens while releasing tension. Notably, sliding of myofilaments occurs during these isotonic actions, particularly as cross-bridge cycling happens, allowing the muscles to contract or elongate accordingly. Thus, the I band would shorten, not lengthen, during isotonic contraction, refuting statement 'b'. Additionally, the statement 'd' is incorrect as myofilaments do not slide during isometric contractions because the muscle does not alter in length.