Abstract
Purpose: The present study evaluated the use of bathroom scales for measuring isometric strength.
Methods: We compared maximal isometric strength measured using bathroom scales and a hand-held dynamometer in 23 healthy individuals without a history of musculoskeletal or neurological disorders. An examiner stood on the bathroom scale and conducted the manual muscle test for each participant. Strength was calculated as the change in the value on the bathroom scale. Maximal isometric strength was measured in the shoulder flexors, knee extensors and hip abductors on the right side.
Results: The mean strengths measured using the bathroom scale were 149.2 ± 33.5 N, 221.1 ± 47.4 N and 172.1 ± 31.7 N for the shoulder flexor, knee extensor and hip abductor, respectively. Similarly, the mean strengths measured using the hand-held dynamometer were 141.7 ± 28.8 N, 212.5 ± 43.8 N and 167.0 ± 28.4 N, respectively. The mean errors of strength measured using the two methods were 5.2 ± 2.6% (CV 86.6%) in the shoulder flexor, 4.5 ± 3.1% (CV 92.6%) in the knee extensor, and 3.1 ± 2.7% (CV 125.9%) in the hip abductor, and the interclass correlation coefficients were 0.98 (p < 0.001) for all three results.
Conclusion: These results indicate that measurements of isometric strength using a bathroom scale and a hand-held dynamometer are in agreement. Thus, bathroom scales can be used to measure isometric strength. This method of measuring isometric strength would be useful for clinically evaluating patients whose activities are restricted because of reduced muscle strength.
