Sleivert, G. C., Esliger, D. W., & Bourque, P. J. (2002). The neuromechanical effects of varying relative load in a maximal squat jump. Medicine and Science in Sports and Exercise, 34(5), Supplement abstract 705.

"Peak power occurs between 15-30% of maximal muscle force in mono-articular movements using small muscles. Conversely, in multi-joint movements requiring the recruitment of many large muscles, peak mechanical power is generated at higher fractions of peak force, usually between 50-70% of one repetition maximum (RM) and power typically is equivalent across a spectrum of loads" (p. S125)

The influence of load on the kinematics and myoelectric manifestations of maximal squat jumps was determined. Active men and women (N = 5) performed maximal squat jumps at loads ranging from 20-80% 1-RM. Surface EMGs of the vastus lateralis and biceps femoris measures were collected.

Load had a substantial effect on force, velocity, power, and peak power. EMG was equivalent across loads indicating that neural drive was independent of load.

Implication. Muscle activation is similar across different loads in squat-jumping but the mechanics are altered depending upon the load.

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