بررسي مقايسه اي اثر كشش به روشهاي هارمونيك و پي ان اف بر شاخصهاي انعطاف پذيري عضله چهارسر ران

Effects of Stretching by P.N.F and Harmonic Techniques on Hamstring Flexibility

Objective: There are many methods for increasing muscle length and decreasing muscle stiffness. In research findings, PNF method has been found to be better than static and ballistic methods. There is another method named Harmonic Technique (introduced by E. Lederman 1947) that has been claimed to be more effective, but there is not enough documentation about this claim. Aim of this study was to compare effects of stretching by PNF and harmonic techniques on hamstring flexibility. Materials & Methods: This research is a Random Clinical Test (R.C.T) study in that 45 colledge students aged 18-35 years were arranged in three groups (Harmonic, P.N.F, and Control). Subjects havenʹt had any painful pathology in low-back and lower extremities for the past six months. Subjects had limited hamstring length (20 degrees deficiency in Active-Knee-Extension test) and hadnʹt professional sport activities. Dependent variablies were muscle stiffness and hamstring length which popliteal angle in Active Knee Extension (AKE) test was its indirect index. In pilot study, reliability of measurement of these variables were approved. Then hamstring muscle of subjects in harmonic and PNF groups were stretched by harmonic and PNF methods for six weeks, 5 minute per day and 3dlwks, whereas control groups were not having any exercise. Results: Findings of this study showed in both used techniques, changes of hamstring length were significant (P=0.000), but in control groups were not significantly change. There wasnʹt significant differences between changes of hamstring length in PNF and Harmonic groups. Only in harmonic group, muscle stiffness had significant changes with. (P<0.03). Conclusion: According to findings of this research, both Harmonic and P.N.F methods equally increased length of hamstring, but harmonic technique can be used as an alternative stretching method in other techniques. May Concelude that Harmonic Technique is better than P.N.F, because the significant changes of stiffness observed only in harmonic group; ie. not only length of muscle increased in this group, but also stiffness decreased significantly which can be an indicator of considerable hiomechanical changes in such muscles and possibly of increase muscle length in P.N.F group found to be not in real improvement flexibility, and tolerance of subjects to stretching in such group has been increased.