Effects of a nine-week core strengthening exercise program on vertical jump performances and static balance in volleyball players with trunk instability.

AIM: The aim of this study was to establish the effects of core strengthening exercise program on trunk instability in response to vertical jump performances and static balance variables in volleyball players. As a core stabilization program aids in developing a stable spine over the pelvis and improves trunk stability this concept should be incorporated in sports tasks involving jump and reach in those with an unstable spine.

METHODS: Forty state level volleyball players with trunk instability were randomly divided into two groups, control ([C] m=10; f=10) and experimental ([E] m=10; f=10). Modified double straight leg lowering test was used to check the degree of trunk instability. Counter movement jump, squat jump, spike jump and block jumps were used to measure jumping abilities and a wobble board test was used to test balance. Pre- and postreadings were noted before and after the nine-week training protocol and statistical data analysis was done using SPSS 16.

RESULTS: After nine weeks of core stabilization training, trunk stability (P<0.001), block difference (BD) in block jump (P<0.01) were enhanced significantly comparing to (C) group using independent T test. Effect size Cohen's d score demonstrated better improvement of spike jump (d=0.25) and block jump (d=0.52) in (E) group. Other jumps and static balance were improved but non-significant when compared between groups.

CONCLUSION: Nine-week strategic core strengthening exercise program increases trunk stability and in turn improves block difference (vertical jump parameter).