1. J Sports Med Phys Fitness. 2014

1. J Sports Med Phys Fitness. 2014 Nov 25. [Epub ahead of print]

Isokinetic knee strength qualities as predictors of jumping performance in
high-level volleyball athletes; multiple regression approach.

Sattler T(1), Sekulic D, Spasic M, Osmankac N, João PV, Dervisevic E, Hadzic V.

Author information:
(1)University of Ljubljana, Faculty of Sport, Ljubljana, Slovenia - [e-mail].

AIM: Previous investigations noted potential importance of isokinetic strength in
rapid muscular performances, such as jumping. This study aimed to identify the
influence of isokinetic--knee--strength on specific jumping performance in
volleyball. The secondary aim of the study was to evaluate reliability and
validity of the two volleyball--specific jumping tests.
METHODS: The sample comprised 67 female (21.96±3.79 years; 68.26±8.52 kg;
174.43±6.85 cm) and 99 male (23.62±5.27 years; 84.83±10.37 kg; 189.01±7.21 cm)
high--volleyball players who competed in 1st and 2nd National Division. Subjects
were randomly divided into validation (n = 55 and 33 for males and females,
respectively) and cross--validation subsamples (n = 54 and 34 for males and
females, respectively). Set of predictors included isokinetic tests, to evaluate
the eccentric and concentric strength capacities of the knee extensors, and
flexors for dominant and non--dominant leg. The main outcome measure for the
isokinetic testing was peak torque (PT) which was later normalized for body mass
and expressed as PT/Kg. Block--jump and spike--jump performances were measured
over three trials, and observed as criteria. Forward stepwise multiple
regressions were calculated for validation subsamples and then cross--validated.
Cross validation included correlations between and t--test differences between
observed and predicted scores; and Bland Altman graphics.
RESULTS: Jumping tests were found to be reliable (spike jump: ICC of 0.79 and
0.86; block--jump: ICC of 0.86 and 0.90; for males and females, respectively),
and their validity was confirmed by significant t--test differences between 1st
vs. 2nd division players. Isokinetic variables were found to be significant
predictors of jumping performance in females, but not among males. In females,
the isokinetic--knee measures were shown to be stronger and more valid predictors
of the block--jump (42% and 64% of the explained variance for validation and
cross--validation subsample, respectively) than that of the spike--jump (39% and
34% of the explained variance for validation and cross--validation subsample,
respectively). Differences between prediction models calculated for males and
females are mostly explained by gender--specific biomechanics of jumping.
CONCLUSION: Study defined importance of knee--isokinetic--strength in volleyball
jumping performance in female athletes. Further studies should evaluate
association between ankle--isokinetic--strength and volleyball--specific jumping
performances. Results reinforce the need for the cross--validation of the
prediction--models in sport and exercise sciences.

PMID: 25422868 [PubMed - as supplied by publisher]

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ผลลัพธ์ (อังกฤษ) 3:

1. J Sports Med Phys Fitness. 2014 Nov 25. [Epub ahead of print]

Isokinetic knee strength qualities as predictors of jumping. Performance in
high-level volleyball athletes; multiple regression approach.

Sattler T (1), Sekulic D Spasic M Osmankac,,, N Jo for PV, O, E Hadzic Dervisevic, V.


Author information (1) University of Ljubljana Faculty of Sport,,, Ljubljana Slovenia - [e-mail].

AIM:Previous investigations noted potential importance of isokinetic strength in
rapid muscular performances such as, jumping.? This study aimed to identify the
influence of isokinetic--knee--strength on specific jumping performance in
volleyball.? The secondary aim of the study was to evaluate reliability and
validity of the two volleyball--specific jumping tests.
METHODS:The sample comprised 67 female (21.96 edge 3.79 years; 68.26 edge 8.52 kg;
174.43 edge 6.85 cm) and 99 male (23.62 edge 5.27 years; 84.83 edge 10.37. Kg; 189.01 edge 7.21 cm)
high--volleyball players who competed in 1st and 2nd National Division. Subjects
were randomly divided. Into validation (n = 55 and 33 for males and females
respectively), and cross--validation subsamples (n = 54 and 34 for. Males, and
femalesRespectively). Set of predictors included, isokinetic tests to evaluate
the eccentric and concentric strength capacities. Of the, knee extensors and
flexors for dominant and non--dominant leg. The main outcome measure for the
isokinetic testing. Was peak torque (PT) which was later normalized for body mass
and expressed as PT / Kg. Block--jump and spike--jump performances. Were measured
.Over, three trials and observed as criteria. Forward stepwise multiple
regressions were calculated for validation subsamples. And then cross--validated.
Cross validation included correlations between and t--test differences between
observed and. Predicted scores; and Bland Altman graphics.
RESULTS: Jumping tests were found to be reliable (spike jump: ICC of 0.79 and
0.86;? Block--jump: ICC of 0.86 and 0.90; for males, and females respectively),
and their validity was confirmed by significant t--test differences. Between 1st
vs. 2nd division players. Isokinetic variables were found to be significant
predictors of jumping performance. In females but not, among males. In females
the, isokinetic--knee measures were shown to be stronger and more valid predictors
.Of the block--jump (42% and 64% of the explained variance for validation and
cross--validation, subsample respectively). Than that of the spike--jump (39% and
34% of the explained variance for validation and, cross--validation subsample
respectively).? Differences between prediction models calculated for males and
females are mostly explained by gender--specific biomechanics. Of jumping.
.CONCLUSION: Study defined importance of knee--isokinetic--strength in Volleyball
jumping performance in female, athletes. Further studies should evaluate
association between ankle--isokinetic--strength and volleyball--specific jumping
performances.? Results reinforce the need for the cross--validation of the
prediction--models in sport and Exercise Sciences.

PMID:25422868 [PubMed - as supplied by publisher]

.