Final answer:
The statement that the force produced during an isometric contraction depends on the number of fibers activated is true. Muscle force correlates with the number of contracting fibers, and this is influenced by the task at hand and the activation of muscle fibers on an all-or-nothing basis.
Step-by-step explanation:
The force produced during an isometric contraction indeed depends on the number of fibers activated. This statement is true. During an isometric contraction, although the length of the muscle does not change, tension is generated. This tension, or muscle force, correlates with the number of muscle fibers that are contracting. In the body, different amounts of force are required for different tasks, which is facilitated by varying the number of active muscle fibers. For a light task like picking up a pencil, only a few muscle fibers need to contract. However, for something that requires greater force, like lifting a heavy weight, a larger number of muscle fibers must be activated.
Muscle fibers work on an all-or-nothing principle, meaning each fiber contracts fully if it is stimulated. When more fibers are stimulated, such as during high-force activities, the overall force produced by the muscle increases accordingly. The generation of force is also influenced by the frequency of action potentials and the number of cross-bridges formed between actin and myosin within the muscle fibers.