Lower-Extremity Strength and Power in Elite Hockey Players With and Without Patellar Tendinopathy

This study investigates whether asymptomatic structural changes impair strength and power generation in hockey players using a between-group analysis based on patellar tendon thickness. Due to a compressed training schedule, testing occurs over consecutive days under standardized conditions. On day one, players provide informed consent and complete injury screening and anthropometric assessments. Strength and power testing is conducted on days two and three by one investigator and analyzed relative to body mass, given the association between patellar tendon thickness and BMI. On day four, a blinded investigator assesses bilateral patellar tendon thickness using ultrasound. On day five, both investigators independently analyze the images. Based on tendon thickness cutoffs, players are classified into healthy, unilateral, or bilateral tendinopathy groups, followed by between-group comparisons of strength and power outcomes.

Screening protocol: A licensed physiotherapist conducts the screening using a binary checklist (yes/no). Criteria include abnormal knee range of motion, knee pain during functional tasks, limping, positive patellar or ligament tests, joint effusion, or unilateral quadriceps atrophy (limb symmetry index <90%). Any positive finding results in immediate exclusion.

Anthropometrics: Body height and body weight are measured privately using a stadiometer and electronic scale, and body mass index is calculated.

Strength testing: Isokinetic leg strength is assessed using a split squat on a robotic resistance device at a concentric speed of 1 m/s. Players perform three maximal repetitions per leg following a standardized warm-up, and peak concentric force is recorded, with the best trial used for analysis.

Power testing: Peak power output is measured using a six-second all-out cycling test on a calibrated ergometer. After a standardized warm-up, resistance is fixed, and players sprint maximally following a countdown. Peak power output is recorded.

Ultrasound examination: Patellar tendon thickness is assessed bilaterally using ultrasound according to standardized guidelines. Players lie supine with the knee flexed ~30°, and longitudinal and transverse scans are obtained. Two independent examiners analyze images, and a tendon thickness >5 mm indicates patellar tendinopathy.

Inclusion criteria

• Male
• Elite ice-hockey player
• ≥ 18 year

Exclusion criteria

• injuries to lower extremity that could influence test perfomance
• deviant passive and active range of motion in the knee joint
• pain in the knee during squatting, lunging, or jumping
• limping while walking
• positive patellar The Royal London Hospital Test
• palpable or visible the knee joint effusion
• positive Lachmann, varus/valgus stress test, patellar apprehension, or Murray's/Apley's test
• hypo- or atrophic quadriceps on only one side (side difference with limb symmetry index < 90%).