A study was performed to evaluate effects of elastic energy stored pre-stretch on the mechanical work output while performing vertical jump. Eight male volunteers of age between 21-29 years old participated in the present study. The present study hypothesized that the vertical jump height during countermovement jumps (CMJ) would be higher than that during squat jump (SJ). During squat jump, a volunteer paused 0.5 sec before making upward movement. The results showed that ground reaction forces and vertical jump displacements were higher in CMJ in comparison to SJ. The study concluded that part of the positive work measured did derive from the recoil of the elastic component of the muscle-tendon complex.