A novel approach to improve hamstring flexibility: A single-blinded randomised clinical trial

BACKGROUND: The hamstrings play a major role in body posture. Shortening or tightness of the hamstrings affects postural alignment and results in possible musculoskeletal pain. OBJECTIVES: The aim of this study was to develop a novel approach to improve hamstring flexibility in young adults. METHOD: A single-blinded randomised clinical trial included 60 participants aged 18–24 with shortened hamstrings recruited from the Hashemite University, Zarqa, Jordan. The range of motion of knee extension was measured with the hip at 90° flexion using a simple goniometer to detect the level of hamstring flexibility. Participants received either a passive hamstring stretch (PS), followed by two sets of 10 tibial nerve neurodynamic technique (ND), or PS followed by three sets of 10 repetitions of active knee extension–quadriceps activation (QA), or PS only. RESULTS: There was a significant improvement of hamstring flexibility in the QA group compared to the PS group (13.4 ± 12.1° vs. 6.2 ± 6.4°, p = 0.05). There was a significant improvement in hamstring flexibility post-intervention compared to pre-intervention in the PS group by 6.2 ± 6.4 (30.5 ± 10.8° vs. 36.6 ± 9.5°, p = 0.001), ND group by 9.3 ± 6.2 (26.7 ± 10.9° vs. 36.0 ± 9.5°, p = 0.001) and QA group by 13.4 ± 12.1 (20.3 ± 9.0° vs. 33.4 ± 8.9°, p = 0.001). CONCLUSION: Quadriceps muscle activation following passive stretching of the hamstrings appears to be superior to the PS and ND techniques in improving hamstring muscle flexibility. CLINICAL IMPLICATIONS: Quadriceps activation following passive hamstring stretching can be used in physiotherapy settings to improve hamstring muscle flexibility.