Examination of reliability and validity in measuring isometric ankle plantar flexion strength using a handheld dynamometer with a belt and metal plate

[Purpose] This study aimed to investigate the reliability and validity of measuring isometric ankle plantar flexion strength using a handheld dynamometer (HHD) with a belt and metal plate. [Participants and Methods] This study enrolled 35 young healthy participants (22 men and 13 women, mean age; 21.2 years). To evaluate reliability, two examiners measured ankle plantar flexor strength twice for all participants using an HHD. To evaluate validity, an examiner measured ankle plantar flexor strength twice in men using an isokinetic dynamometer (IKD). [Results] Intra-rater reliability was almost perfect for examiners A and B, whereas their interrater reliability was substantial. Pearson’s correlation coefficients for the HHD and IKD in men were not significantly correlated. [Conclusion] The intra- and interrater reliabilities of HHD measurements, as evaluated by the data for all participants, were high. However, the validity of HHD measurements evaluated by men was low if IKD-measured values were used as a reference.