Relationship between lower limb power and dynamic stability in volleball players

Abstract Introduction As in all team sports, lower limb power is an important quality of any player. Especially when it comes to volleyball, a game that relies on jumping performance on almost every action except reception. Another crucially important quality of the lower limbs is dynamic stability. Without the latter, the frequency of injuries rises, and that is something any coach or player wants to avoid. The question arises: Are the two qualities related? Aim The study aimed to investigate the correlation between lower limb power and force measured using an inertial flywheel training/measuring device and dynamic stability evaluated through the Y balance test. Material and method The Y balance test was used for evaluating the lower limb dynamic stability of 8 Romanian volleyball players. In addition, using an inertial flywheel training system (kBox 4 Pro, Exxentric, Sweden) and kMeter II measuring device the following parameters where measured: average force AvF (N), average power AvP (W), concentric peak power ConPP (W), eccentric peak power EccPP(W). The relative peak power RPP (W/kg) was calculated by dividing concentric peak power by the weight of the volleyball player. The subjects performed 8 maximal squats using the kBox harness and the L (0,05 kgm2) flywheel Results Composite reach distance (CRD) means for the lower limbs have been compared using the t-test and although there is a difference of 1.8%, it isn’t significant, (p<0,001). We have found a direct correlation between the average composite reach distance and relative peak power (r=0.71, p=0.045) and also with the average power (r=0.75, p=0.032) of the lower limbs. The composite reach distance for the right leg correlates with the relative peak power (r=0.73, p=0.036); average force (r=0.73, p=0.039), and average power (r=0.77, p=0.024). For the left leg, however, the only correlation found with the CRD is the average power (r=0.75, p=0.044). Conclusions The medium composite reach distance CRDM is directly correlated with the average lower limb power and relative peak power but due to the small sample size, the power of this effect is unknown. CRDR (right leg) significantly correlates with relative peak power, average power but also with average force whereas CRDL (left leg) only correlates with average power. This does not come as a surprise because all the subjects are right side dominant. There is no significant difference between CRDR and CRDL p<0.001. This is quite important because stability asymmetries of the lower limbs may lead to injury.