Final answer:
Electrical activation of myofibers leads to muscle contraction and force production, while mechanical tension refers to external forces on the muscle. Studies have primarily investigated the role of mechanical tension in triggering hypertrophy.
Step-by-step explanation:
The primary variable determining force production in muscles is the number of myofibers that receive an action potential from the controlling neuron. Electrical activation of the myofibers leads to muscle contraction and force production. Mechanical tension, on the other hand, refers to the force applied to the muscle externally, such as lifting weights. While both aspects have been investigated in relation to hypertrophy, studies have primarily focused on the role of mechanical tension in triggering hypertrophy.