Hamstring FlexibilityPNF+NMESNCT07075497
Effects of Combining PNF With NMES in Young Football Players
A study testing Neuromuscular electrical stimulation (NMES) and Contract-Relax PNF (crPNF) in people with Hamstring Flexibility and Hamstring Muscle Tightness, run by Cardenal Herrera University at 1 site in Spain.
Trial 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. Read more about this study
- Who is it for?
- Ages 10 to 18 yearsHealthy volunteers can take part
- Conditions the study is for
- Hamstring Flexibility, Hamstring Muscle Tightness
- What is being tested?
- Neuromuscular electrical stimulation (NMES) and Contract-Relax PNF (crPNF)
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 47 participants
- Where
- 1 siteSpain
- Study dates
- 11 Jul 2025to 27 Jul 2025
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 10 to 18 years
- All sexes
- Healthy volunteers accepted
- Child, Adult
Who may be able to join
- Active football players who train at least 3 days a week.
- Ages between 10 and 18 years.
Who cannot join
- 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.
Trial locations and contacts
1 site in 1 country.
Spain1 site
University Ceu Cardenal Herrera
Alfara del Patriarca, Valencia, 46113
About this study
Official title: Short Term Effects of Proprioceptive Neuromuscular Facilitation Combined With Neuromuscular Electrical Stimulation in Young Football Players: a Randomized Clinical Trial
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.
Read the detailed description
Hamstring strains are increasingly common in sports, particularly in football, where they are among the most frequent injuries. Stretching techniques such as proprioceptive neuromuscular facilitation (PNF) are commonly used to improve muscle flexibility and reduce injury risk. A specific variant, contract-relax PNF (crPNF), involves alternating passive stretching with voluntary muscle contractions. Recent approaches suggest that applying neuromuscular electrical stimulation (NMES) during the contraction phase of crPNF may further enhance its effectiveness.
This study aims to compare the short-term effects of two active stretching protocols on hamstring flexibility in young male football players. One group will perform crPNF with sham NMES, while the other will perform crPNF with NMES during the contraction phase. A secondary objective is to assess whether either protocol affects vertical jump performance, a key ability in football.
- Conditions
- Hamstring Flexibility, Hamstring Muscle Tightness
- Being tested
- Neuromuscular electrical stimulation (NMES), Sham Neuromuscular electrical stimulation (NMES), Contract-Relax PNF (crPNF)
- Keywords
- hamstring flexibility, football, Propioceptive Neuromuscular Facilitation, Neuromuscular Electrical Stimulation, Sports Injury Prevention, Athletic Performance, Muscle Stretching, Hamstring Muscle Function
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
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.
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 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.
| Study group | Role | What they receive |
|---|---|---|
| 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. Receives: 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. Receives: Other: Neuromuscular electrical stimulation (NMES); Other: Contract-Relax PNF (crPNF) |
What is being measured
The primary outcome is the main question the study is designed to answer.
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.
Measured: 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.
Measured: Before and inmediately after the intervention
Secondary outcomes (1)
The Counter Movement Jump
The Counter Movement Jump is validated and standardized in adolescents for measuring jumping ability. The instructions by Petrigna et al. are followed to perform the jump. The My Jump App is used, which has high reliability and validity for measuring vertical jump height in centimeters. A greater height indicates a greater jumping ability.
Measured: Before and inmediately after the intervention
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted20 Jul 2025
- Study start11 Jul 2025
- Primary completion24 Jul 2025
- Study completion27 Jul 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Hamstring FlexibilityStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind
- Who is masked
- Outcomes assessor
- Enrolment
- 47 participants (actual)
Sponsor and investigators
- Lead sponsor
- Cardenal Herrera University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Juan F. Lisón Párraga, Dr, Cardenal Herrera University
- Investigators
- Juan Francisco Lisón Párraga, Dr, Principal investigator, Cardenal Herrera University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07075497
- Sponsor's protocol ID
- UNIVERSITY CARDENAL HERRERA-97
- Acronym
- PNF+NMES
- Status last verified
- Nov 2025
- First submitted
- 11 Jul 2025
- Last updated
- 17 Nov 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 17 Nov 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Short Term Effects of Proprioceptive Neuromuscular Facilitation Combined With Neuromuscular Electrical Stimulation in Young Football Players: a Randomized Clinical Trial
- ClinicalTrials.gov ID
- NCT07075497
- Acronym / sponsor ID
- PNF+NMES / UNIVERSITY CARDENAL HERRERA-97
- 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
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 47 participants (actual)
- Lead sponsor
- Cardenal Herrera UniversityUniversity, hospital or other
- Study start
- 11 Jul 2025 (actual)
- Primary completion
- 24 Jul 2025 (actual)
- Study completion
- 27 Jul 2025 (actual)
- First posted
- 20 Jul 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
Hamstring strains are increasingly common in sports, particularly in football, where they are among the most frequent injuries. Stretching techniques such as proprioceptive neuromuscular facilitation (PNF) are commonly used to improve muscle flexibility and reduce injury risk. A specific variant, contract-relax PNF (crPNF), involves alternating passive stretching with voluntary muscle contractions. Recent approaches suggest that applying neuromuscular electrical stimulation (NMES) during the contraction phase of crPNF may further enhance its effectiveness.
This study aims to compare the short-term effects of two active stretching protocols on hamstring flexibility in young male football players. One group will perform crPNF with sham NMES, while the other will perform crPNF with NMES during the contraction phase. A secondary objective is to assess whether either protocol affects vertical jump performance, a key ability in football.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| contract-relax proprioceptive neuromuscular facilitation with sham NMES (crPNF + sham NMES) | Placebo comparator | Other: Sham Neuromuscular electrical stimulation (NMES), Other: Contract-Relax PNF (crPNF)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. |
| Neuromuscular Electrical Stimulation (NMES + crPNF) | Experimental | Other: Neuromuscular electrical stimulation (NMES), Other: Contract-Relax PNF (crPNF)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. |
Who may qualify
- Ages
- 10 to 18 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Child, Adult
Key inclusion criteria (2 listed)
- Active football players who train at least 3 days a week.
- Ages between 10 and 18 years.
Key exclusion criteria (4 listed)
- 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.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Neuromuscular electrical stimulation (NMES)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. | Other | Neuromuscular Electrical Stimulation (NMES + crPNF) |
| Sham Neuromuscular electrical stimulation (NMES)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. | Other | contract-relax proprioceptive neuromuscular facilitation with sham NMES (crPNF + sham NMES) |
| Contract-Relax PNF (crPNF)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. | Other | Neuromuscular Electrical Stimulation (NMES + crPNF), contract-relax proprioceptive neuromuscular facilitation with sham NMES (crPNF + sham NMES) |
Primary outcome
The Popliteal Angle Test
Time frame: Before and inmediately after the intervention
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.
The Sit & Reach Test
Time frame: Before and inmediately after the intervention
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.
1 secondary outcome
The Counter Movement Jump
Time frame: Before and inmediately after the intervention
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 17 Nov 2025.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Juan Francisco Lisón Párraga, Dr principal investigator
Cardenal Herrera University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Neuromuscular electrical stimulation (NMES) and Contract-Relax PNF (crPNF) in people with Hamstring Flexibility and Hamstring Muscle Tightness, run by Cardenal Herrera University at 1 site in Spain.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 17 Nov 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Spain. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
The Popliteal Angle Test (time frame: Before and inmediately after the intervention). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 17 Nov 2025.