Background Patellar tendinopathy is a common overuse injury in jumping sports, with higher prevalence in volleyball players. Different risk factors are associated with patellar tendon problems, including training load. Despite different treatment options, rates of chronicity and recurrence are high. Therefore, the high prevalence and the challenging treatment underlines the importance of prevention.

Objective Investigate the relation between tendon load and the response of patellar tendon structure of volleyball players.

Design Observational prospective study.

Setting The study was performed with elite volleyball players during the preseason.

Patients (or Participants) A total of 17 elite male volleyball players from Dutch volleyball league.

Interventions (or Assessment of Risk Factors) Training load, including jump frequency and Rating or Perceived Exertion (RPE), were measured every training and match during 7 weeks.

Main Outcome Measurements Tendon structure was measured using the Ultrasound Tissue Characterization (UTC), which quantifies the structure of the tendon (percentages of four echo-types).

Results On average, players spent 624±215 minutes on training and matches per week with a RPE of 13.9±2.1 indicating 'somewhat hard' intensity. Jump frequency was 278±122 per week. Higher load parameters (volume, intensity and load) resulted all in a higher decrease of echo-type I (p<0.05). Higher volume and load resulted in a higher decrease of echo-type II (p<0.05). Higher cumulative weekly volume and cumulative weekly loads between the first and the last UTC were related to significant higher decreases in echo-type I (p<0.05), but not related for echo-type II. No significant relations were found for jump frequency. None of the load parameters were related to echo-type III and IV.

Conclusions The present study showed that load was related to changes in echo-types over a 7 week preseason in elite volleyball players. A higher amount of load was related to greater echo pattern changes.