Effects of Combining PNF With NMES in Young Football Players

NCT07075497 | Completed

• 1 other identifier: UNIVERSITY CARDENAL HERRERA-97
• Study Type: interventional
• Target: 47
• Locations: 1 country
• Sites: 1

Brief Summary

Hamstring muscle injuries are common in sports like football and often lead to extended periods of inactivity. This study aims to compare the effects of two different stretching programs on hamstring flexibility, with a secondary focus on jumping performance in young football players. One group will perform a proprioceptive neuromuscular facilitation (PNF) stretching protocol combined with neuromuscular electrical stimulation (NMES), while the other group will follow the same PNF protocol with a placebo NMES.

Conditions

Hamstring Flexibility; Hamstring Muscle Tightness

Keywords

hamstring flexibility; football; Propioceptive Neuromuscular Facilitation; Neuromuscular Electrical Stimulation; Sports Injury Prevention; Athletic Performance; Muscle Stretching; Hamstring Muscle Function

Outcome Measures

Primary Outcomes (2)

• The Popliteal Angle Test

  The Popliteal Angle Test is validated for measuring hamstring extensibility. Participants are placed in the supine position. A researcher holds the hip at a 90° flexion and passively extends the knee until the participant feels a strong stretch without pain. The examiner records the knee extension degrees at that moment using an inclinometer. The test is repeated three times, and the average is obtained. A full knee extension corresponds to a value of 0 degrees, and a higher number of degrees indicates greater hamstring shortening.

  Before and inmediately after the intervention

• The Sit & Reach Test

  The Sit \& Reach Test has high intra-examiner reliability and is validated for measuring hamstring extensibility. For its execution, participants are placed in a long sitting position with the soles of their feet against the base of the measurement box. Keeping their knees extended, they reach for the maximum possible distance in the box with their fingers. The test is repeated three times, and the average is obtained. Values are recorded in centimeters, where a greater distance indicates a higher degree of hamstring extensibility.

  Before and inmediately after the intervention

Secondary Outcomes (1)

• The Counter Movement Jump

  Before and inmediately after the intervention

Study Arms (2)

contract-relax proprioceptive neuromuscular facilitation with sham NMES (crPNF + sham NMES)

PLACEBO COMPARATOR

Participants sat in long-sitting with maximal knee extension and pelvic anteversion controlled by elastic straps over the pelvis and distal thigh. Two 5×5 cm self-adhesive electrodes were placed on the hamstrings: one two fingerbreadths below the gluteal fold (proximal) and one over the distal third of the muscle belly. Sham NMES delivered biphasic symmetric rectangular pulses (50 Hz, 250 µs) at the sensory threshold (minimal intensity eliciting only a slight tingling without visible muscle response). Each of three cycles comprised a 10 s maximal voluntary isometric hamstring contraction ("Squeeze…!") against the fixed table, immediately followed by a 30 s passive stretch to a moderate-strong but non-painful tension ("Stretch…!"). A primary researcher ensured consistent limb positioning and strap tension; a secondary researcher monitored timing and cued contractions by lightly supporting the heels.

Other: Sham Neuromuscular electrical stimulation (NMES); Other: Contract-Relax PNF (crPNF)

Neuromuscular Electrical Stimulation (NMES + crPNF)

EXPERIMENTAL

Participants sat in long-sitting with maximal knee extension and pelvic anteversion controlled by elastic straps over the pelvis and distal thigh. Two 5×5 cm self-adhesive electrodes were placed on the hamstrings: one two fingerbreadths below the gluteal fold (proximal) and one over the distal third of the muscle belly. NMES delivered biphasic symmetric rectangular pulses (50 Hz, 250 µs) at each participant's maximal motor threshold without discomfort or pain; the resulting milliamperage was recorded for each leg and used during all contraction phases. Each of three cycles comprised a 10 s maximal voluntary isometric hamstring contraction ("Squeeze…!") with NMES applied at the recorded intensity, immediately followed by a 30 s passive stretch to a moderate-strong but non-painful tension ("Stretch…!"). A primary researcher ensured consistent limb positioning and strap tension; a secondary researcher monitored timing and cued contractions by lightly supporting the heels.

Other: Neuromuscular electrical stimulation (NMES); Other: Contract-Relax PNF (crPNF)

Interventions

Neuromuscular electrical stimulation (NMES) OTHER

NMES is applied during each 10-second isometric hamstring contraction using an Enraf Nonius TensMed S82 stimulator delivering biphasic, symmetric rectangular pulses at 50 Hz with a 250 µs pulse width. Two 5 × 5 cm self-adhesive electrodes are placed on the hamstrings-one approximately two finger-breadths below the gluteal fold and the other over the distal third of the muscle belly. Stimulation intensity is individually titrated to each participant's maximal motor threshold-eliciting a strong, yet painless, contraction-and the exact milliamperage is recorded for each leg. Elastic straps over the pelvis and distal thigh maintain pelvic anteversion and knee extension. During each session, one researcher secures limb positioning while a second adjusts and logs NMES intensity and cues the timing of the 10 s contraction and ensuing 30 s passive stretch.

Neuromuscular Electrical Stimulation (NMES + crPNF)

Sham Neuromuscular electrical stimulation (NMES) OTHER

Sham NMES is delivered during each 10 s isometric hamstring contraction using an Enraf Nonius TensMed S82 stimulator with biphasic, symmetric rectangular pulses (50 Hz, 250 µs pulse width). Two 5 × 5 cm self-adhesive electrodes are placed on the hamstrings-one two finger-breadths below the gluteal fold and one over the distal third of the muscle belly. Intensity is individually set to the sensory threshold, defined as the minimal current producing a slight tingling without any visible muscle response; this milliamperage is recorded for each leg. Elastic straps over the pelvis and distal thigh maintain pelvic anteversion and full knee extension. During each session, one researcher secures limb positioning while a second adjusts and logs the NMES intensity and cues the 10 s contraction timing.

contract-relax proprioceptive neuromuscular facilitation with sham NMES (crPNF + sham NMES)

Contract-Relax PNF (crPNF) OTHER

The crPNF Group engages in an isolated contract-relax proprioceptive neuromuscular facilitation (crPNF) stretching protocol. Participants are positioned in a long sitting posture with maximum knee extension until they feel a moderate-strong stretch sensation, without pain. Each stretch lasts for 30 seconds, followed by a 10-second maximal voluntary isometric contraction of the hamstrings. Participants complete three cycles of stretch and contraction. One researcher maintains the stretch position while a second researcher controls the timing of the stretching and contractions.

Neuromuscular Electrical Stimulation (NMES + crPNF); contract-relax proprioceptive neuromuscular facilitation with sham NMES (crPNF + sham NMES)

Eligibility Criteria

• Age: 10 Years - 18 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Child (0-17), Adult (18-64)

You may qualify if:

• Active football players who train at least 3 days a week.
• Ages between 10 and 18 years.

You may not qualify if:

• Are currently engaged in a structured hamstring-stretching programme.
• Present with acute low back pain.
• Have sustained a hamstring injury within the past 6 months.
• Have undergone spinal or abdominal surgery within the past 6 months.

Sponsors & Collaborators

• Cardenal Herrera University: lead

Study Sites (1)

University Ceu Cardenal Herrera

Alfara del Patriarca, Valencia, 46113, Spain

Location

Study Officials

• Juan Francisco Lisón Párraga, Dr

  Cardenal Herrera University

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: OUTCOMES ASSESSOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Study Record Dates

• First Submitted: July 11, 2025
• First Posted: July 20, 2025
• Study Start: July 11, 2025
• Primary Completion: July 24, 2025
• Study Completion: July 27, 2025
• Last Updated: November 17, 2025

Record last verified: 2025-11

Locations

ES (1)