Ability and Reproducibility to Exert Force for Testing Muscle Strength by A Handheld Dynamometer of The Various Examiners: Sex and Body Weight Factors

Abstract

Kiatkulanusorn S, Luangpon N, Suato BP, Klarod K, Srijunto W, Wipatin P, Kinandana P, Watechagit S, Kaoien C, Werasirirat P. Ability and Reproducibility to Exert Force for Testing Muscle Strength by A Handheld Dynamometer of The Various Examiners: Sex and Body Weight Factors. JEPonline 2023;26(5):11–23. A minimum measurement error of the muscular strength test with hand held dynamometer (HHD) can be generated by a good plan if the examiner recognizes their ability to exert force for the test. The purpose of this study was to determine the true magnitude of forces that can be exerted by testers in different configurations. Reproducibility score of each test force produced by each tester was also described. Five experienced examiners from different sex and weights were challenged to test the same 14 target resistance loads (3 to 70 kg) over 2 sessions. Intra- and inter-rater reliability were explored in terms of the intraclass correlation coefficient (ICC), the standard error of measurement (SEM), and the minimal detectable change (MDC). The results showed that the maximum effort of each examiner was 60% to 70% body weight. Only male overweight examiner could complete 70 kg test load. The HHD results showed no statistically significant effect of BMI (P = 0.397) but a statistically significant effect of session (P < 0.001), sex (P = 0.039), and resistance load (P < 0.001). Excellent reliability was found in intra- examiner of all load (ICC = 0.920-0.997) and inter-examiner of a resistance load of 30 kg or less (ICC = 0.963-0.993). Intra-rater exhibited a greater measurement error at low resistance load, in particular < 10 kg (SEM, 1.9%-7.32% and MDC, 4.44%-17.07% for all examiner) and men examiners (SEM, 7.23-7.32% and MDC, 16.88%-17.07% for < 10 kg test load). Inter-rater showed greater measurement errors at low resistance load and under men examiners, in particular < 10 kg (SEM: 2.72%-4.50%, women examiner and 6.79%-7.28%, men examiner, MDC: 6.35%-10.51%, women examiner and 15.85%-16.98%, men examiner). In conclusion, the HHD test within the limit of the force generated by the examiner, the very weak muscle should be the critical concern to minimize the measurement error, especially for male examiners.