Reliability and Validity of Hip Extensor Strength Measurement in Sitting Position by a Handheld Dynamometer in the Older Adults.

BACKGROUND AND PURPOSE: Muscle strength measurements with the handheld dynamometer are sometimes performed according to manual muscle testing. However, measuring hip extensor muscle strength in the prone position is difficult, since the some older adults had kyphosis or flexion contracture of the lower limbs. On the contrary, there is the standing position method of manual muscle testing, which alternated to those malalignments; however, it is known that the muscle strength of the lower limb that is not measured affects the measurement result. Hence, we devised the hip extensor strength measurement in a sitting position for healthy male in previous studies. This study examined the reliability and validity of the sitting measurement by a handheld dynamometer in older adults.

METHODS: Participants were 40 older adults (age [SD] = 82.4 [4.3] years). Measurements of the isometric muscle strength of the hip extensor using handheld dynamometer in 3 postures (sitting, standing, and prone positions) were conducted twice. Furthermore, a surface electromyogram was used to measure the activity of the gluteus maximus and the semitendinosus muscle. The reliability of muscle strength in each posture was examined with Cronbach α coefficient, intraclass correlation coefficients (ICCs1,1), and Bland-Altman analysis. The concurrent validity of muscle strength for the sitting and standing positions with reference to the prone position was examined with Spearman rank correlation and Bland-Altman analysis. Furthermore, muscle strength and muscle activity were compared between each posture.

RESULTS: The Cronbach α coefficient was 0.75. For each posture, the ICC1,1 was 0.86 to 0.87, with no systematic error in the sitting and prone positions. The sitting and standing positions were significantly associated with the prone position (rs = 0.72 and 0.42), with no systematic error between the sitting and prone positions. Proportional error was showed between the standing and prone positions (P < .01). There was no significant difference in muscle strength between any posture. The muscle activity of gluteus maximus in sitting position was significantly higher than that in standing position (P < .05).

CONCLUSION: The measurement of hip extensor muscle strength in the sitting position is a reliable and valid method in older adults, which can be effective even when the prone position is not possible.