Comparison of muscle strength imbalance in powerlifters and jumpers

The purpose of the study was to examine the bilateral and unilateral force production difference in powerlifters (bilateral) and field jumpers (unilateral) to determine the existence of leg dominance. Nineteen powerlifters (PL; n = 11) and field jumpers (J; n = 8) were included in the study. Five different no arm swing countermovement jumps were randomized for testing: (a) double-leg jump; (b) dominant leg-specified double-leg jump; (c) nondominant leg-specified double-leg jump; (d) dominant leg-specified single-leg jump; and (e) nondominant leg-specified single-leg jump. The force, velocity, and power were measured via a forceplate. The Limb Symmetry Index (LSI% = (1-ND limb/D limb)×100%) was calculated for force imbalance between the dominant (N) and nondominant (ND) limb between PL and J. Based on the analysis, PL (mean = 2.75 ±2.45%) had a lower LSI (p <0.05) than J (mean = 6.81 ± 5.16%). The single-leg jumps show a (p <0.05) significantly higher force and power and a significantly lower velocity than double-leg jump for both D and ND leg than double-leg jump. Finally, the ratio between bilateral and unilateral exercise for PL and J is 2.36:1.36 and 2.38:1, respectively. In summary, sport-specific demands between PL and J may contribute to the occurrence of the imbalance force production between limbs. This phenomenon is important for the strength coach to acknowledge, to perform an appropriate strength balance test during the offseason, and to implement a training program to reduce the force disparity between limbs. Neglecting the development of force imbalance between limbs may predispose healthy players to injury.