Final answer:
The active force generated by a muscle depends primarily on the calcium concentration within muscle fibers, as it regulates the binding of myosin to actin during muscle contraction. The frequency of action potentials and resulting calcium release also affect the force production, as does the inherent elasticity of muscle tissue.
Step-by-step explanation:
The active force a muscle can generate primarily depends upon the calcium concentration within the muscle fibers. When a muscle contracts, calcium ions bind to troponin, which leads to the exposure of the active site on actin, allowing myosin to form cross-bridges and thereby shorten the sarcomeres, resulting in muscle contraction. Additionally, the active force is influenced by the number of myofibers that receive an action potential, as more recruited fibers result in a greater force. This process can be modulated by the frequency of action potentials, with higher frequencies increasing force production due to more calcium flooding the tropomyosin and allowing for more cross-bridge formation.
Other factors influencing muscle force include the elasticity of muscle tissue, as seen with the contribution of elements such as titin and elastin fibers, which allow the muscle to recoil back to its original length after being stretched or contracted. However, the main element in force generation during contraction is the calcium concentration and its role in the regulation of the interaction between actin and myosin within the sarcomeres.