Velocity-specific knee strength between professional and under-17 female volleyball players.
Alexandre R M Pelegrinelli, Laís F Dela Bela, Mariana F Silva and 8 others
PMID 31309163WHAT IT FOUND
Professional female volleyball players had greater knee extension strength than under-17 players at all tested speeds.
Hamstring-quadriceps ratios were similar and below the reference balance value, and no injuries were measured.
Key findings
01Professional players had significantly greater knee extension peak torque, total work and mean power than under-17 players at all tested velocities on both limbs, with no significant differences in angle of peak torque.
02Professional players had greater knee flexion total work and mean power at all tested velocities, with greater peak torque at some speeds on the dominant and non-dominant sides.
03No significant difference was found for the hamstring-quadriceps ratio on either the dominant or non-dominant limb.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
Only 21 female volleyball players were studied, and the design was cross-sectional, so it cannot show whether strength differences cause injury or change over time. Training frequency and intensity between age groups were not controlled, so maturity and training history cannot be separated. Isokinetic testing required acceleration to reach the set speed, which may have reduced usable data, especially at higher speeds. Stabilising straps were used, but compensatory movements may still have affected the results. The athletes were injury-free and tested at the start of the season, so findings may not apply to injured players.
The easy way to misread this
Do not read the lower hamstring-quadriceps ratios as proof that these athletes are at higher knee injury risk. The study measured strength only, did not follow injuries, and the ratios were not significantly different between the two groups.