Information about a piece of news titled Differences in mechanical and material properties between elite volleyball players with and without patellar tendinopathy
Differences in mechanical and material properties between elite volleyball players with and without patellar tendinopathy
Intoduction
Results from this collaboration between the Department of Physical Performance and the Oslo Sports Trauma Research Center at the Norwegian School of Sport Sciences were recently published in British Journal of Sports Medicine.
It is well-known, that athletes performing sports with high demands on lower limb explosive strength, such as weightlifting, volleyball, football, long jump and high jump, often suffer from jumper’s knee (patellar tendinopathy). A prevalence as high as 45% has been reported for male elite volleyball players. However, little knowledge available on patellar tendon properties, and risk factors and functional consequences of jumper’s knee are not fully understood.
Participants with achilles tendinopathy have shown a greater cross sectional area, lower stiffness and Young’s modulus compared to healthy Achilles tendons. Despite these findings on achilles tendinopathy, these data are lacking for patellar tendons.
Part of ongoing volleyball project
With these differences between affected and healthy Achilles tendons in mind, we wanted to investigate if there was a difference in tendon properties between patellar tendons of elite volleyball players with jumper’s knee and healthy matched players. In addition, we wanted to analyze the jump performance of these players.
We identified 17 male elite volleyball players with a history of jumper’s knee and 18 healthy matched controls from a 5-year study on junior elite volleyball players.
The subjects were evaluated with respect to maximal vertical jump performance and patellar tendon mechanical (stiffness) and material properties (Young’s modulus) were examined using ultrasonography.
Briefly explained, tendon stiffness is a measure on how much force is needed to lengthen the tendon a given distance.
Lower stiffness and Young’s modulus, but better jumping performance
In line with previous clinical findings, we found a larger proximal cross-sectional area of the patellar tendon in injured players compared to healthy. Also, tendons with jumper’s knee presented 20% lower stiffness and 15% lower Young’s modulus compared to healthy tendons.
However, the difference between counter movement and squat jump height was higher in the group with jumper’s knee compared to the group of healthy players (3.4 vs 1.2 cm).
In other words, tendinopathic volleyball players were good in utilizing the stretch-shortening cycle when jumping (see similar results from a side-project).
Tendon properties were, however, not measured in the 5-year prospective study, so we can only speculate whether or not the differences in mechanical properties are the consequence or the cause of chronic tendinopathy.
Implications
The observed differences in jumping ability among players with and without a “jumper´s knee” suggest that players´s jumping ability may contribute to identify those players who run into a greater risk for developing patellar tendinopathy.
Consequently, training programs can be optimized and training load adjusted to prevent the development of tendinopathy. Altered jump techniques and/or the amount of jumps during training sessions have been suggested by other studies to be important.
This project was a collaboration of the Department of Physical Performance and the Oslo Sports Trauma Research Center. Masterstudent and volleyball player Christian Helland was supervised by Jens Bojsen-Møller, Truls Raastad, Olivier R Seynnes, Marie M Moltubakk, Vidar Jokobsen, Håvard Visnes and Roald Bahr.
Download the article in British Journal of Sports Medicine.
Read also "Jumping expsoure a risk factor for developing Jumper´s Knee".