Isometric muscle strength in youth assessed by hand-held dynamometry: a feasibility, reliability, and validity study.

Purpose: To determine, with respect to measurement of maximal isometric torque (MIT) using a specific hand-held dynamometer (HHD) protocol, (1) protocol feasibility over a wide age range, (2) intra- and interrater reliability, (3) standard error of measurement, and (4) concurrent validity.

Methods: The MIT of selected upper and lower limb muscle groups was assessed (n = 74; age = 4-17.5 years) using a standardized, HHD protocol. Testing was repeated in 20 adolescents (n = 10 for each muscle group), who were also assessed with a Cybex dynamometer.

Results: The protocol was feasible for all participants. Mean intra- and interrater reliability [intraclass correlation coefficient (ICC)] varied from 0.75 to 0.98, except for ankle dorsiflexor interrater reliability (mean ICC = 0.67). The standard error of measurement varied from 0.5 to 4.9 Nm and was highest for hip extensors. Mean concurrent validity (ICC) varied from 0.78 to 0.93, except for ankle plantar flexors (mean ICC = 0.48).

Conclusions: Our HHD protocol was feasible over a wide age range and most MIT values were valid and reliable.