CHRONIC EFFECT OF PROPRIOCEPTIVE NEUROMUSCULAR FACILITATION STRETCHING ON FLEXIBILITY AND STRENGTH
Keywords:
Contract-relax PNF stretching / Agonist/antagonist stretching / In-season training; Range of motion / Hamstring/Quadriceps ratioAbstract
Stretching is usually included in the regular training program or part of warm-up activity before exercises. However, it is not that popular during the in-season training as it could compromise the muscle strength. Contract-relax proprioceptive neuromuscular facilitation (CR-PNF) stretching is generally known as an effective method to increase the joint range of motion, implying flexibility, but the chronic effect on muscle strength was not much studied. The aim of this study was to investigate the chronic effects of 4-week CR-PNF stretching on muscle strength, i.e. the knee flexor (hamstrings) and knee extensor (quadriceps) during the in-season training of professional soccer players. Thirty-one male professional soccer players received the CR-PNF stretching of hamstring and quadriceps muscles for 4 weeks during the in-season training. Hip and knee range of motion and hamstring flexibility (sit-and-reach test) were measured before, at the end of each week and two weeks after the stretching session in order to see if the range of motion was maintained. Knee flexion and extension isokinetic strengths were tested before and two weeks after the stretching session. Isokinetic Hamstring/Quadriceps (H/Q) ratios were also assessed. The range of motion was progressively increased from the baseline measurement as can be observed since week 2 for hamstring (hip and knee extension) and week 3 for quadriceps (hip and knee flexion), similarly for both dominant and non-dominant legs. At two weeks after the intervention, the range of motion was not significantly different from week 4 (p>0.05) but significantly improved as compared to the baseline (p<0.05). Isokinetic knee flexion strength was significantly improved (p<0.05) but not the case for extension strength (p>0.05). H/Q ratios were significantly improved after the intervention (p<0.05). It was concluded that during the in-season training, CR-PNF stretching was effectively able to increase the flexibility without the detrimental chronic effect on muscle strength. Improved muscle balance (H/Q ratio) consequently from the increased isokinetic flexion strength also suggested the positive effect on injury prevention. (Journal of Sports Science and Technology 2018; 18(2): 9-20) Keywords: Contract-relax PNF stretching / Agonist/antagonist stretching / In-season training; Range of motion / Hamstring/Quadriceps ratio
*Corresponding author: Korakod PANICH
College of Sports Science and Technology Mahidol University,
Nakhon Pathom, Thailand 73170
E-mail: [email protected]
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