May 2011

Volleyball findings link training volume to symptoms of patellar tendinopathy

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Jumping ability not implicated

Hard work can make up for a lack of natural talent in sports, but research from Norway suggests that may not be true when it comes to the risk of patellar tendinopathy (jumper’s knee) in young volleyball players.

In two separate studies of junior high school volleyball players presented in Monaco in April, investigators from the Oslo Sports Trauma Research Center found that high sport-specific training loads were associated with increased risk of patellar tendinopathy but that baseline jumping ability was not.

Both studies utilized data from a single Patellar Tendinopathy Cohort analyzed over a five-year period. The training study prospectively followed 140 male and female athletes for a mean of 1.8 years; all were asymptomatic at baseline but 28 went on to develop symptoms of patellar tendinopathy. Training volume was determined from an internet-based weekly training diary as well as interviews with players and coaches.

Athletes who developed jumper’s knee spent significantly more hours per week in training than those who remained asymptomatic, with indoor volleyball training accounting for most of that difference. Volumes of strength, flexibility, and other types of training did not differ significantly between groups.

The findings are generally consistent with those of a 2004 American Journal of Sports Medicine study from the same group, in which high-level male volleyball players with existing symptoms of patellar tendinopathy reported training for more hours per week than asymptomatic players. However, in that study, strength training accounted for the only statistically significant component of that difference. And because the players were already symptomatic at baseline, it’s possible that the difference simply reflects the fact that weight training was less painful than volleyball-specific training or jump training.

The jumping ability study prospectively followed 113 male and female athletes for the same mean length of time in as the previous study; 19 went on to develop symptoms of jumper’s knee, but only three were girls, so the analysis focused on male athletes only. Standing jump height and countermovement jump height was assessed at baseline and twice a year during the study period.

Jumping ability at baseline was not significantly different in those who became symptomatic and those who did not, either with respect to either jump test. However, although jumping ability improved in both groups, those who remained asymptomatic demonstrated significantly greater improvements on both jump tests than their injured counterparts.

The jumping ability findings appear to contrast with those of the 2004 study, in which the players with patellar tendinopathy had significantly higher composite jump scores (representing eight different jump tests, including standing jumps with varying degrees of added load) than the asymptomatic players. The authors designed the composite jump score to reflect a player’s ability to load the extensor muscles, and theorized that the observed differences suggest that players with patellar tendinopathy may be subjected to higher loads while playing volleyball than asymptomatic players.

It may also be worth noting that the composite jump score was based on a rating system in which each individual test result was assigned a score according to its position relative to the highest and lowest scores among all players’ results for that test. But in terms of jump heights for each specific test, there were no statistically significant differences between the symptomatic and asymptomatic groups.

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