Effectiveness of hamstring stretching using a pressure biofeedback unit for 4 weeks: A randomized controlled trial.
Jin-Oh Ahn, Jong-Hyuck Weon, Eun-Kyung Koh and 1 others
PMID 33005074WHAT IT FOUND
Four-week hamstring stretching while using a pressure unit to keep the pelvis tilted forward gave a 21.0° larger gain in knee-extension angle measured in that position than stretching without it; measured without the unit, the groups did not differ.
Key findings
01After stretching, the group using the pressure unit gained 27.4° on the knee-extension test done with the unit, compared with 6.4° in the group stretching without it.
02The improvement in the knee-extension test done with the unit was 21.0° greater in the pressure-unit stretching group than in the control group.
03When the knee-extension test was done without holding the pelvis with the unit, the two groups did not differ significantly.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
People with current or recent low back pain were excluded, and the study did not measure pain or function, so it cannot show that stretching with the unit helps patients with low back pain. Only 40 of the 48 participants who began were analysed; 8 stopped because of pain or discomfort, and the analysis was not intention-to-treat. The investigator knew which group each participant was in, so measurement could be biased despite participant blinding. Participants were young adults with short hamstrings, so results may not apply to older adults or people without short hamstrings. The pressure unit was used both to guide stretching and to control position during testing; the study did not show that gains measured with the unit carry over to everyday movement.
The easy way to misread this
Do not read the 21.0° difference as proof that pressure-unit stretching reduces low back pain. The participants had no current or recent low back pain, and the outcome was a laboratory knee-extension angle, not pain or function.