Hamstring muscle injuries are common in basketball and result in long periods of inactivity. This study aims to compare two different stretching programs to assess their effects on hamstring flexibility and, secondarily, on jumping ability in young basketball players. One program uses a special stretching technique called proprioceptive neuromuscular facilitation (PNF), while the other uses the same stretching but adds electrical stimulation (NMES).
Hamstring strains are increasingly common in sports, particularly in football and professional basketball, where they are the fourth most frequent injury. Stretching, especially when combined with techniques like proprioceptive neuromuscular facilitation (PNF), is a key method used to reduce the risk of these injuries. PNF, which involves alternating stretches with muscle contractions, is widely regarded for improving muscle flexibility. Recently, stretching combined with neuromuscular electrical stimulation (NMES) has also shown promise for increasing flexibility. A variant of PNF called contract-relax PNF (crPNF) has been proposed, where NMES is applied during the contraction phase to further enhance flexibility gains. However, there are no studies on the short-term effects of crPNF and crPNF + NMES in young male basketball players, a group known for higher degrees of hamstring shortening. This study aims to compare the short-term effects of crPNF and crPNF + NMES on hamstring flexibility in young male basketball players and assess whether one technique is superior to the other. A secondary goal is to determine if either stretching protocol negatively impacts vertical jump ability, an important skill in basketball.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
44
Neuromuscular electrical stimulation (NMES) is applied during an isometric contraction. The NMES uses a symmetrical biphasic rectangular pulse (50Hz frequency and 300 µs phase width) delivered through an Enraf Nonius TensMed S82 electrostimulator. Two 5x9 cm electrodes are placed on the hamstrings, and participants adjust the current to a moderate-strong, yet painless, contraction level. During the intervention, one researcher maintains the stretch position while another researcher controls the current intensity and monitors the timing of both stretching and contractions.
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 20 seconds, followed by a 5-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.
University Ceu Cardenal Herrera
Alfara del Patriarca, Valencia, Spain
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.
Time frame: 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.
Time frame: Before and inmediately after the intervention
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 (Figure 2C). 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.
Time frame: Before and inmediately after the intervention
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