RELATIONSHIP OF CORE STRENGTH AND ISOKINETIC KNEE STRENGTH WITH VERTICAL JUMP PERFORMANCE IN VOLLEYBALL

Background: The game of Volleyball requires the players to perform dynamic movements in receiving the ball and performing explosive movements in spiking and blocking. Vertical jump (VJ) becomes one of the basic motor ability in volleyball owing to its frequent involvement during spiking, blocking, and setting the ball for attack. Although considerable work has been done, the relationship between core strength (Trunk Flexion (TF) & Back Extension (BE)) and vertical jump remains unclear. Thus, the present study was aimed at finding relationship between core strength-endurance and vertical jump performance. Method: 20 male players (Age=18.05±0.76 years; Height=192.75±5.88cm; Weight=77.67±7.37kg) from Indian National U-20 Volleyball team were tested on an Isokinetic Dynamometer at 600*s-1, 900*s-1 and 1200*s-1 angular speeds for strength testing, on DAVID systems for trunk flexion and back extension and on sergeant test for vertical jump. Results: Core strength-endurance (TF & BE) and isokinetic concentric Quadriceps strength at 1200*s-1 (CDQ120) for dominant leg were significantly positively correlated to vertical jump (TF vs VJ: r=0.507, p=0.023; BE vs VJ: r=0.453, p=0.045; CDQ120 vs VJ: r=0.595, p=0.006) while isokinetic strength for non-dominant leg approximated significance with increasing velocities. Also, core strength (TF & BE) was significantly positively related with FlightTime (FT) (TF vs FT: r=0.497, p=0.026; BE vs FT: r=0.568, p=0.009). Conclusion: The significant positive correlation of core strength with vertical jump and FlightTime establishes core strength as an integral component of sports training in Volleyball. Although, eccentric quadriceps strength and hamstring strength were not positively correlated to vertical jump, they help in safe landing mechanism and reduce injury-risks. The small sample size of the study warrants further investigations with larger sample size to confirm the findings. Article visualizations