Acute Effects of Contract-Relax PNF With and Without Neuromuscular Electrical Stimulation on Hamstring Flexibility and Jump Performance in Adolescent Soccer Players: A Randomized Controlled Trial.

International journal of sports physical therapy · 2026 · RCT · PT
Carlos Salvador-Huerta, Pedro Azanon-Nogueira, Eloi Suárez-Pazos, Valeria Betancourt-Cabeza, Irene Lazcano-Nogueira, Andrea Porcu, Ángel Manuel de la Hera-Sastre, Juan J Amer-Cuenca, Juan Francisco Lisón

Adding motor-level electrical stimulation to a PNF stretching routine gave adolescent soccer players no more flexibility than the same routine with a placebo tingle. Neither protocol changed jump height. The evidence here does not support adding NMES for an extra flexibility boost.

Key findings

1

Adding motor-threshold NMES to a PNF-CR stretching protocol did not produce greater hamstring flexibility gains than the same protocol with sensory-threshold (placebo) stimulation; no significant between-group difference was found for either the Sit-and-Reach or the Popliteal Angle.

2

Both groups showed statistically significant within-group improvements in hamstring flexibility after the single session, but the authors note the magnitude of change was modest and should be read as acute shifts in extensibility measures rather than clinically meaningful individual changes.

3

Neither protocol produced a significant change in vertical jump height, indicating no acute impairment of explosive lower-limb performance in either group.

MethodologyResultsClinical Relevance

Single-blind randomized controlled trial. Sixty-four participants were randomized across two intervention arms and assessed at twelve weeks for the primary outcome…

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