STRETCHING RESEARCH METHODOLOGY HAS BEEN POOR
Decoster, L. C., Cleland, J., Altieri, C., & Russell, P. (2005). The effects of hamstring stretching on range of motion: a systematic literature review. Journal of Orthopaedic and Sports Physical Therapy, 35(6), 377-387.
The literature regarding the most effective positions, techniques, and durations of stretching to improve hamstring muscle flexibility were reviewed. Data-based studies that included randomized and clinical trials were reviewed according to specific inclusion/exclusion criteria (Physiotherapy Evidence Database (PEDro) 10-point scale and descriptive information about the stretching parameters employed in the research). Healthy Ss (N = 1338) were included in the reviewed studies. Methodological quality scores ranged from 2 to 8 (mean ± SD, 4.3 ± 1.6). Several methodological flaws were frequently recognized, including failure to conceal group allocation or perform blinded assessment. All studies reported improvements in range of motion after stretching.
Overall, methodological quality was poor, with only 6 of the 28 studies achieving a score between 6 and 8. It was difficult to identify confidently the most effective hamstring stretching method. Hamstring stretching increased range of motion with a variety of stretching techniques, positions, and durations.
Implication. Any form of hamstring stretching increases range of motion. The literature is not clear if any method is dangerous or produces side-effects. Since research methodology is very poor in the area of flexibility/stretching, one should read articles critically and conservatively before adopting opinions.
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