Overview

This study investigates the immediate effects of different peripheral electrical nerve stimulation protocols applied to the femoral nerve on quadriceps strength in athletes with patellar tendinopathy. Patellar tendinopathy is a common overuse injury that often reduces quadriceps activation and limits sports performance. Peripheral percutaneous nerve stimulation (PPNS) and transcutaneous electrical nerve stimulation (TENS) are frequently used in rehabilitation, but their frequency-dependent effects on muscle strength are not well established.

In this randomized crossover trial, each participant receives three stimulation protocols in separate sessions: high-frequency PPNS (100 Hz), low-frequency PPNS (2 Hz), and conventional TENS. All stimulation is delivered at the maximal tolerated motor threshold and, for PPNS conditions, under ultrasound guidance. Quadriceps maximal isometric strength is evaluated using an isometric force sensor before and after each intervention.

The primary objective is to compare the acute changes in maximal voluntary contraction (MVC) following each stimulation protocol. The study aims to clarify whether different stimulation frequencies can enhance, reduce, or have no effect on quadriceps strength in this athletic population.

By identifying frequency-specific neuromodulatory responses, this study may help clinicians and sports practitioners select the most appropriate stimulation parameters to optimize rehabilitation and performance in individuals with patellar tendinopathy.

Eligibility

Inclusion Criteria:

• Adults aged 18 to 40 years.
• Recreational or competitive athletes with clinically diagnosed patellar tendinopathy for at least 3 months.
• Ultrasound-confirmed patellar tendinopathy, including hypoechoic areas, tendon thickening, or neovascularization consistent with clinical diagnosis.

Presence of pain during tendon-loading activities (e.g., jumping, running, squatting).

• Ability to perform maximal voluntary isometric contractions of the quadriceps.
• Ability to comply with all study procedures and attend all experimental sessions.
• Written informed consent obtained prior to participation.

Exclusion Criteria:

• Previous knee surgery or traumatic knee injury within the past 12 months.
• Complete or partial patellar tendon rupture.
• Neurological disorders affecting lower limb strength or motor control.
• Contraindications to electrical stimulation, including implanted electrical devices (e.g., pacemaker).
• Current lower-limb radiculopathy or neuropathy.
• Skin infections, open wounds, or dermatological conditions at the stimulation site.
• Use of analgesics, anti-inflammatories, or corticosteroid injections within the past 48 hours.
• Participation in another interventional study in the previous 30 days.
• Pregnancy or suspected pregnancy.