Effect of backpack shoulder straps length on cervical posture and upper trapezius pressure pain threshold.
Osama Ragaa Abdelraouf, Hamada Ahmed Hamada, Ali Selim and 2 others
PMID 27799665WHAT IT FOUND
Backpack strap length affected neck angle and upper trapezius pain sensitivity, but the paper's text and table disagree about whether long straps made them worse.
Key findings
01Twenty-five healthy young men were measured without a backpack and after 15 minutes of treadmill walking with short straps and long straps.
02The paper reported that upper trapezius pain threshold and craniovertebral angle differed across the three backpack conditions.
03The written results and Table 1 disagree about direction: the text says long straps reduced both measures, while the table lists higher values for long straps.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The sample was 25 healthy young men with no upper-extremity musculoskeletal disorder or pain in the prior 6 months, so it does not show what happens in patients with neck or shoulder pain. The measurements were taken immediately after 15 minutes of treadmill walking at 2 km/h, not during normal school or work backpack carrying, and no pain, injury, or long-term outcome was tested. The written results and Table 1 disagree about the direction of change, so the paper does not clearly show whether long straps worsened or improved the measures. The study used surrogate outcomes, pressure pain threshold and craniovertebral angle, rather than symptoms, function, or injury.
The easy way to misread this
Do not conclude that long straps definitely worsened posture and trapezius sensitivity, because the paper's text says reductions while Table 1 lists higher values. Also, this was a short-term lab study in healthy young men, so it does not establish that backpacks cause pain or prescribe a safe strap length.