The test-induced warm-up effect on hamstring flexibility tests.
Wootaek Lim
PMID 38510156WHAT IT FOUND
Performing six consecutive trials of hamstring flexibility tests before measurement significantly increased flexibility.
This test-induced warm-up effect persisted for at least two minutes, meaning baseline measurements taken without prior trials may underestimate muscle length and overestimate stretching benefits.
Key findings
01Six consecutive trials of the active knee extension or straight leg raise test significantly increased flexibility compared to pre-test measurements.
02The increase in flexibility remained significant after a two-minute rest period following the warm-up trials.
03There was no significant difference in flexibility gains between performing the warm-up trials with a five-second hold at the end range versus without hold.
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 collegiate students with hamstring tightness, so results may not apply to patients with pathology or different flexibility profiles. A single therapist performed all measurements, which limits generalizability to multi-therapist settings. The study did not include a control group that received no warm-up trials, so it is unclear how much of the flexibility gain is due to the test-induced warm-up versus natural variation or learning effects. The sample size was small (n=30).
Declared interests
The author declared no conflicts of interest. The research was funded by Woosong University Academic Research Funding.
The easy way to misread this
Do not assume that adding a five-second hold at the end range during warm-up trials makes the assessment more effective. The study found no significant difference between holding and not holding for the primary outcomes, and the authors suggest that holding may introduce additional stretch effects that complicate the measurement of inherent muscle length.