Intrasession and Intersession Reliability of Isometric Trunk and Hip Strength Measurements Using the Portable Tension Dynamometer.

CONTEXT

The trunk/pelvis is an important link between the upper- and lower-extremities. Therefore, assessing strength of the trunk and hip muscles that control the segments is clinically meaningful. While an isokinetic dynamometer can be used to measure trunk strength, the equipment is expensive and not portable.

OBJECTIVE

To test the reliability of simple trunk and hip strength measures that utilize a bar, straps, and a portable tension dynamometer.

DESIGN

Test-retest reliability study.

SETTING

Biomechanics research laboratory. Patients (or Other Participants): Twenty college-age individuals (10 males/10 females, age = 20.9 [3.7] y) participated.

INTERVENTION(S): The participants attended 2 testing sessions, 1 week apart. The participants' trunk-flexion, rotation, and hip abduction strength were measured at each session.

MAIN OUTCOME MEASURES

Peak trunk flexion, rotation, and hip abduction forces were normalized to the participant's body weight (BW). In addition, hip-abduction torque was calculated by multiplying the force times the leg length and normalized to BW. The trial data from both sessions were used to calculate the intrasession reliability, and the averages from the 2 sessions were used to calculate the intersession reliability. Intraclass correlation coefficients, SEM, and minimal detectable change were calculated to evaluate reliability of measures.

RESULTS

The intrasession intraclass correlation coefficients (SEM) for trunk flexion, rotation, hip abduction, and hip abduction torque were .837 (5.2% BW), .978 (1.3% BW), .955 (1.0% BW), and .969 (5.8 N·m/BW), respectively. The intersession reliability for trunk flexion, rotation, hip abduction, and hip abduction torque were .871 (4.3% BW), .801 (3.8% BW), .894 (1.5% BW), and .968 (5.9 N·m/BW), respectively.

CONCLUSIONS

The measures of trunk and hip abduction strength are highly repeatable within a session. The reliability of the measures between sessions was also good/excellent with relatively small SEM and minimal detectable change. The tests described in this study can be used to assess changes in trunk/hip strength over time.