Comparison of effects of joint flexibility on the lumbo-pelvic rhythm in healthy university students while bending the trunk forward.
Yuko Takahashi, Takehiko Yamaji
PMID 32184539WHAT IT FOUND
Healthy university students with poor flexibility bent forward using more lumbar spine motion and less hip motion than students with normal flexibility, and lower back and hamstring muscle activity stopped at different points in hip flexion.
Key findings
01Poor flexibility participants used a larger proportion of lumbar spine motion (49.7 ± 10.4%) and a smaller proportion of hip motion (47.9 ± 13.6%) during total forward bending than normal flexibility participants (41.7 ± 7.1% and 58.1 ± 11.5%).
02In the final 76-100% phase of forward bending, hip motion contributed 60.9 ± 24.7% in poor flexibility and 87.1 ± 28.9% in normal flexibility.
03Biceps femoris muscle activity stopped earlier in normal flexibility (50.0 ± 7.3% of maximal range of motion) than in poor flexibility (58.9 ± 13.8% of maximal range of motion).
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only healthy university students with no injury history and an Oswestry Disability Index score of 0, so it cannot be applied to people with low back pain or disability. It was cross-sectional and did not follow participants over time, so it cannot show that poor flexibility causes low back pain. The sample was small (47 participants) and may not generalise beyond healthy university students. The flexibility grouping was based on whether the palms could touch the floor while bending forward with straight knees, rather than on pain or clinical outcomes. The authors state they were unable to clarify enough the effects of poor flexibility and that future work is needed on joint location and ground reaction forces.
Declared interests
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors, and the authors declared no conflicts of interest.
The easy way to misread this
Do not conclude that poor flexibility causes low back pain. The study was cross-sectional, included healthy university students without low back pain, and measured movement and muscle activity, not pain outcomes.