Excellent reliability of toe strength measurements in children aged ten to twelve years achieved with a novel fixed dynamometer

BackgroundStronger toe flexor muscles improve performance outcomes in children, including balance, sprinting, jumping and side stepping. Toe flexor strength (TFS) is recommended as part of the clinical assessment of foot function in children. Fixed dynamometry, rather than handheld, is the gold standard of measurement; however, it can be prohibitively costly. No fixed dynamometer reliability studies on toe flexion have been conducted in children to date.Research questionsDoes the novel fixed hand-held dynamometer (HHD) protocol provide reliable intra-rater and test-retest measurements of toe flexor strength in children aged 10 to 12?MethodsTwo trials were recorded from 14 healthy children (10–12 years), 7–14 days apart by the same rater. A Lafayette HHD (model 01163) measured peak force. The HHD was secured in a mobile custom mould below a step with a strap, which secured the foot of the participant. The receptor pads of the HHD were level with the upper surface of the step, maintaining neutral toe joints at rest. The participant was seated on an adjustable stool to ensure the hip, knee and ankle were each at 90° flexion, with the testing foot flat on the upper surface of the step. The averages of three maximal five second efforts were used for data analysis using a two-way mixed effects model with repeated measures ANOVA (intraclass correlation coefficient ICC 3,3). Standard error of measurement (SEM) was calculated to determine the absolute between trial variability.ResultsThe novel fixed HHD protocol provided excellent test-retest reliability with small measurement error for hallux (ICC 3,3 = 0.93, 95 % CI 0.78−0.98, SEM = 4.31 N) and lesser toe flexor strength testing (ICC 3,3 = 0.96, 95 % CI 0.87−0.99, SEM = 1.86 N).SignificanceThe fixed HHD protocol described in this study has excellent reliability for the test-retest evaluation of children’s toe flexor strength.