Influence of Testing Position on the Reliability of Hip Extensor Strength Measured by a Handheld Dynamometer

Abstract

Hip extensors belong to an important muscle group that controls standing, walking and other functional activities. The prone position (PP) is commonly used to measure the strength of the hip extensors; however, the reliability of such measurements is poor. The aim of this study was to determine the effect of different testing positions, that is, the PP and the prone standing position (PSP), on the reliability of measurements of hip extensor strength. Intrasession reliability and interrater reliability studies were performed on 47 and 16 normal subjects, respectively. The muscle strength of the hip extensors was tested in both the PP and PSP. A handheld dynamometer and break test were used to measure the strength. Relative reliability and absolute reliability were assessed in both PP and PSP. For relative reliability, the intraclass correlation coefficient (ICC) was used to examine the level of reproducibility among measurements. Absolute reliability, the smallest real difference (SRD), was used to provide information on measurement error. The results showed that the reliability was better in PSP than in PP. For relative reliability, the values of ICCs were excellent in the intrasession reliability study, in both PP (ICC1,3 = 0.92) and PSP (ICC1,3 = 0.94). However, the interrater reliability was only excellent in PSP; the ICC2,3 were 0.92 in PSP and 0.65 in PP. For absolute reliability, the values of the SRD were much lower in PSP (29.8) than in PP (71.8), indicating that the measurement of muscle strength in PSP was more stable and had smaller measurement error than in PP. Changing the testing position from the traditional "prone" to "prone-standing" effectively improved both the relative reliability and the absolute reliability.

Retest reliability of measuring hip extensor muscle strength in different testing positions in young people with cerebral palsy

“…The need for participants to exert more effort in lifting the weight of their leg before exerting force on the dynamometer may have contributed to reduced reliability compared to the supine position. The standing position has not been evaluated before in the measurement of hip extensor strength in young people with cerebral palsy although high levels of retest reliability (ICC = .92) have been reported in using a modified standing position to assess hip extensor muscle strength in adults without impairment [26]. This position was thought to be advantageous because it is a more functional position to assess the strength of the hip extensors.…”

Hip extension strength: Description and validity of a new procedure applied to older women

“…Yet in older individuals and patients with various pathologies, hip extension strength can be re-duced. Studies in which HHD has been used to measure hip extension strength describe procedures where the tested individual is prone and no compensation is made for gravity [2,10,16]. To this end previous research has employed manual muscle testing [9,13], fixed force gauges [13,14], isokinetic dynamometry [4,5], or hand-held dynamometry (HHD) [2,10,16].…”

Validity of the Handheld Dynamometer Compared with an Isokinetic Dynamometer in Measuring Peak Hip Extension Strength

“…The intertester, intratester, and intrasession reliability of hip extension measurement using an HHD has been well documented in healthy participants in the prone position (intertester intra-class correlation [ICC]=0.65–0.93; intratester ICC=0.77–0.96) 4 , 19 , 20 and in the standing position (intertester ICC=0.82–0.84; intratester ICC=0.91–0.94). 21 Higher intertester (ICC=0.92) and intrasession (ICC=0.94–0.99) reliability values have been reported using a prone standing position 6 , 22 in which the participant is standing but the upper body is supported on a plinth ( Figure 1 ). Studies have suggested that the prone position does not allow as great a muscle contraction as the prone standing position.…”

“… 1 – 5 Hip extension strength is an important measurement in orthopaedic pathologies because it plays a key role in functional mobility such as ambulation and negotiating stairs. 6 – 8 Research has suggested that weak hip extensors are linked to several orthopaedic pathologies, including low back pain 9 , 10 and hip osteoarthritis. 11 – 13 A valid and objective measure to quantify hip extension strength is needed to explore these relationships.…”

“…Studies have suggested that the prone position does not allow as great a muscle contraction as the prone standing position. 6 , 22 In the prone standing position, the hip is flexed and hip extensor muscle fibres and lever arm are lengthened, allowing a favourable length–tension relationship and thus optimizing hip extension torque production. 23 Waters and colleagues 24 found that in standing, when increasing hip flexion from 0° to 90°, hip extension force production more than doubled.…”