Biernat, R, Trzaskoma, Z, Trzaskoma, Ł, and Czaprowski, D. Rehabilitation protocol for patellar tendinopathy applied among 16- to 19-year old volleyball players. J Strength Cond Res 28(1): 43–52, 2014—The aim of the study was to investigate the efficacy of rehabilitation protocol applied during competitive period for the treatment of patellar tendinopathy. A total of 28 male volleyball players were divided into two groups. Fifteen from experimental group (E) and 13 from control group (C) fulfilled the same tests 3 times: before the training program started (first measurement), after 12 weeks (second measurement) and after 24 weeks (third measurement). The above-mentioned protocol included the following: USG imagining with color Doppler function, clinical testing, pain intensity evaluation with VISA-P questionnaire, leg muscle strength and power and jumping ability measurements. The key element of the rehabilitation program was eccentric squat on decline board with additional unstable surface. The essential factor of the protocol was a set of preventive functional exercises, with focus on eccentric exercises of hamstrings. Patellar tendinopathy was observed in 18% of the tested young volleyball players. Implementation of the presented rehabilitation protocol with eccentric squat on decline board applied during sports season lowered the pain level of the young volleyball players. Presented rehabilitation protocol applied without interrupting the competitive period among young volleyball players together with functional exercises could be an effective method for the treatment of patellar tendinopathy.