This randomized, double-blind, placebo-controlled clinical trial evaluates the effects of oral beta-hydroxy-beta-methylbutyrate (HMB) supplementation combined with an eccentric exercise and extracorporeal shockwave rehabilitation program on pain, tendon morphology, and neuromuscular performance in athletes with patellar tendinopathy.

Thirty athletes with a confirmed diagnosis of patellar tendinopathy are randomized to receive either HMB supplementation (3 g/day) or placebo during an 8-week rehabilitation program. Participants are evaluated at baseline, week 4, and week 8.

The primary outcome is pain and functional limitation assessed using the Victorian Institute of Sport Assessment-Patella (VISA-P) questionnaire. Secondary outcomes include patellar tendon thickness measured by ultrasound imaging, countermovement jump (CMJ) performance, and neuromuscular performance variables derived from an incremental squat test using a linear position transducer.

The aim of the study is to determine whether HMB supplementation enhances clinical recovery and neuromuscular performance when combined with a standardized rehabilitation program compared with placebo.

Patellar tendinopathy is a degenerative tendon disorder frequently observed in athletes involved in jumping and running sports. The condition is characterized by localized tendon pain, functional impairment, and structural alterations of the patellar tendon. Standard rehabilitation programs commonly include eccentric exercise protocols and extracorporeal shockwave therapy to promote tendon adaptation and pain reduction.

Beta-hydroxy-beta-methylbutyrate (HMB), a metabolite of the amino acid leucine, has been associated with anti-catabolic effects and improved muscle recovery. HMB supplementation may potentially enhance neuromuscular adaptations and recovery during rehabilitation programs.

This study evaluates the effects of HMB supplementation when combined with a standardized rehabilitation program including eccentric exercise and extracorporeal shockwave therapy in athletes with patellar tendinopathy.

This randomized, double-blind, placebo-controlled clinical trial includes 30 athletes aged 18 to 49 years with clinically diagnosed patellar tendinopathy. Participants are randomly assigned to one of two groups:

HMB Group: Participants receive oral HMB supplementation (3 g/day) combined with eccentric exercise and extracorporeal shockwave therapy.

Placebo Group: Participants receive placebo capsules (sucrose) combined with the same eccentric exercise and extracorporeal shockwave therapy program.

The intervention lasts 8 weeks. Assessments are performed at baseline, week 4, and week 8.

The primary outcome measure is the VISA-P questionnaire, which assesses pain and functional limitations related to patellar tendinopathy. Secondary outcome measures include patellar tendon thickness measured by ultrasound imaging, countermovement jump (CMJ) performance, and neuromuscular performance variables obtained from an incremental squat test using a linear position transducer, including peak power, peak power relative to body mass, and mean velocity at peak power.

Exercise sessions follow a structured eccentric decline squat protocol combined with periodic extracorporeal shockwave therapy sessions using a Storz Medical MP100 device.

The objective of the study is to determine whether HMB supplementation improves clinical outcomes, tendon thickness, and neuromuscular performance compared with placebo when both groups follow the same rehabilitation program.

Inclusion Criteria:

• Age between 18 and 49 years
• Clinical diagnosis of patellar tendinopathy confirmed by a physician and physiotherapist
• Competitive athlete in sports involving repetitive knee loading (e.g., basketball, volleyball, handball, athletics)
• Minimum training frequency of three sessions per week
• No knee surgery within the previous 12 months
• No nutritional supplementation within the previous 3 months
• No injection therapy (analgesics or platelet-rich plasma) within the previous 12 months
• Non-smoker
• Signed informed consent

Exclusion Criteria:

• Any musculoskeletal injury other than patellar tendinopathy affecting performance
• Systemic disease affecting musculoskeletal function
• Inability to comply with the rehabilitation or supplementation protocol

Double-blind study. Both participants and investigators were unaware of group assignment (HMB or placebo). Capsules were identical in color and appearance, and the allocation code was not disclosed until all data were collected.