Assessing the Reliability of Handheld Dynamometry and Ultrasonography to Measure Quadriceps Strength and Muscle Thickness in Children, Adolescents, and Young Adults.
Kelly Rock, Christa Nelson, Odessa Addison and 1 others
PMID 33563044WHAT IT FOUND
Handheld dynamometry and ultrasound produced repeatable quadriceps strength and thickness readings in healthy children, adolescents, and young adults.
Using the top two of three strength trials made readings more consistent. The study did not test patients with motor impairment.
Key findings
01Knee extension torque measured with handheld dynamometry was reliable, with measurement error averaging 2.38 Nm across three trials and 1.61 Nm when using the two highest trials.
02Ultrasound thickness measurements of rectus femoris and vastus lateralis were highly repeatable, with agreement values of 0.998 to 1.000 within the same rater and 0.914 to 0.993 between raters.
03Quadriceps strength was higher at 90° knee flexion than at 35° knee flexion, and strength and muscle thickness were greater in older age groups.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The participants were healthy volunteers with no neurological or muscular disorder and no lower extremity surgery or serious injury, so the results do not show how these measures perform in children with motor impairments. 30 participants were spread across 4 age groups, so each age group was small; the adolescent subgroup had 7 participants. The methods say 30 participants, but the conclusion says 26 individuals, and the paper does not explain the difference. Age groups were based on chronological age, not puberty or maturity markers, so they may not reflect biological development. Inter-rater ultrasound reliability was checked for only the first 10 participants, and same-rater re-measurement after about one year was done for only 10 participants. Muscle thickness was measured only in supine, relaxed positions, not in the strength testing positions, so the study did not show how thickness changes with joint angle. Torque was estimated using tibial shaft length, which is an approximate moment arm rather than the exact distance from resistance to joint axis.
Declared interests
No potential conflict of interest was reported by the authors.
The easy way to misread this
Do not conclude that handheld dynamometry and ultrasound are validated for children with cerebral palsy, stroke, or other motor impairments. The study tested only healthy children, adolescents, and young adults, and the authors only suggest that these methods could be useful in future work with clinical populations.