Author(s): Manish Shukla

Abstract:
Vertical jump is one of the key determinants of success in explosive events like volleyball. A great amount of vertical jump is required to attack and block in the game of volleyball. Isokinetic knee extensor strength has been reported to be highly related to vertical jump. In the present study, two different modes of isokinetic knee strength (concentric and eccentric) were investigated for their relationship with vertical jump performance in sergeant jump test. A total of 18 U-20 volleyball players (Age 18.05±0.72yrs; Height 192.17±5.83cm and Body Weight 77.64±7.29 kg) from Indian U-20 national squad were employed for the purpose of the study. They were tested in laboratory at 60⁰/s, 90⁰/s and 120⁰/s angular velocity using the Cybex isokinetic dynamometer (Humac Norm). The vertical jump performance was measured as difference between maximum standing height (with full arm reach overhead) and maximum vertical jump (VJ=62.81±5.33cm). A significant moderate correlation was observed between concentric knee extensor strength at 120⁰/s angular velocities for dominant (r= 0.582; p<0.05) and non-dominant legs (r= 0.519; p<0.05) while eccentric knee strength was not related to jump height at all angular velocities. Although only 120⁰/s angular velocity was significantly related to jump height, concentric knee strength at remaining angular velocities (60⁰/s and 90⁰/s) was close to being significant. Also, it implies that explosive and power training in concentric mode must be focused in order to increase vertical jump performance. Also, eccentric mode must be included in training to safeguard landing and avoiding injuries.

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