Short Term Effects of Proprioceptive Neuromuscular Facilitation Combined With Neuromuscular Electrical Stimulation in Young Football Players: a Randomized Clinical Trial

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.

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.

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.

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.