Final answer:
Muscular force production is primarily determined by the number of myofibers receiving action potentials, and can be influenced by the frequency of these signals. Muscle strength relates to myofibril and sarcomere counts within these fibers, which can be modified through hormonal influence or exercise, leading to hypertrophy or atrophy. Muscle tension also depends on the cross-bridge formation between actin and myosin within the muscle fibers.
Step-by-step explanation:
The factors affecting muscular force production include the number and stimulation frequency of myofibers, muscle fiber composition, length-tension relationship, and the number of cross-bridges formed. When lifting objects of varying weight, such as a pencil versus a piano, the motor cortex sends different amounts of action potentials to the biceps muscle
. For a lighter object, fewer myofibers are stimulated compared to something heavier where nearly all myofibers are recruited for maximum force production. Increasing the frequency of action potentials can further increase muscle force as it leads to more calcium interacting with tropomyosin, enhancing muscle contraction.
Muscle strength and hypertrophy are influenced by the amount of myofibrils and sarcomeres, and can be affected by factors such as hormones, stress, and the use of anabolic steroids. In contrast, muscle atrophy can occur when there is decreased use of a skeletal muscle, as seen in limbs immobilized in a cast or in diseases like polio.
The amount of tension a muscle can produce is also dependent on the formation of cross-bridges between actin and myosin which is dictated by sarcomere length. Optimal overlap between thin and thick filaments allows for maximum cross-bridge formation, and hence, maximal tension and power.