A tactical athlete weighs 220lb (91kg) and has a 1RM squat of 330lb (150kg). Which exercise results in the most motor unit recruitment in the vastus lateralis muscle?

The most motor unit recruitment in the vastus lateralis muscle is achieved during the eccentric phase of contact after a drop jump. When an athlete performs a drop jump, they experience a rapid stretch of the muscle as they absorb the impact of landing. This eccentric phase generates significant tension and utilizes the stretch reflex, activating a large number of muscle fibers to stabilize and control the body’s descent.

The eccentric loading creates a high degree of muscle tension, leading to an increase in the recruitment of motor units as the muscle works to manage the impact. This mechanism not only promotes extensive motor unit activation but also prepares the muscles for the concentric phase that follows, enhancing performance in explosive movements.

In contrast, the other exercises do not elicit the same level of motor unit recruitment. Isometric leg extensions, while effective for targeting specific muscles, do not engage the stretch reflex to the same extent as an eccentric movement. The concentric phase of the squat at 75% of 1RM is certainly demanding but typically does not recruit as many motor units as an eccentric movement, especially following a drop. The weighted step-up provides a good workout but lacks the sudden and high-intensity recruitment seen in landing from a drop jump.