Effects of trunk stability on isometric knee extension muscle strength measurement while sitting.
Masahiro Hirano, Masahiro Gomi, Munenori Katoh
PMID 27799673WHAT IT FOUND
When sitting is fully stabilized with straps, handheld dynamometer readings for knee extension strength match those from a gold-standard machine.
Without this stability, handheld readings are likely underestimated due to body compensation. Ensure patients are strapped in securely to get accurate strength measures.
Key findings
01Handheld dynamometer and isokinetic dynamometer measurements showed no significant difference when the trunk and pelvis were stabilized by straps.
02Measurements taken in a sitting position without straps are presumed to be underestimated because of compensatory movement from the hips and trunk.
03The two instruments showed a high correlation (r ≥ 0.96) for knee extension torque values.
STILL TO COME
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What it does not show
The study was conducted on healthy young adults (19–22 years), so results may not apply to older adults, children, or patients with neurological conditions who cannot follow instructions or maintain posture. The measurement condition was highly controlled and different from typical clinical setups, as the HHD was physically linked to the dynamometer chair's support pillar. The study did not test patients with very high muscle strength, such as athletes, where the handheld device's upper limit might be reached.
Declared interests
No specific funding sources or conflicts of interest are declared in the provided text.
The easy way to misread this
Do not assume a handheld dynamometer is inaccurate. The issue is not the device, but the lack of stabilization. Without straps securing the trunk and pelvis, the patient compensates, leading to a falsely low strength reading rather than a device error.