Test-retest reliability of a hip strength assessment system in varsity soccer players

Abstract

Objective: To investigate test-retest reliability of a hip strength assessment system (GroinBar).

Design: Test-retest reliability study.

Setting: Laboratory.

Participants: Twenty asymptomatic varsity soccer players.

Main outcome measures: Maximal isometric hip strength (adduction, abduction, internal and external rotation, flexion and extension) was assessed using the GroinBar. Intraclass correlation coefficient (ICC) and relative standard error of measurement (SEM) were calculated to evaluate reliability of peak (ICC_3,1) (highest peak within 3 trials) and average peak (ICC_3,3) (average of 3 trials) force and rate of force development (RFD). Hotelling's T², were also used to compare bilateral and reciprocal ratios between dominant and non-dominant leg.

Results: ICC for both peak force and RFD values revealed moderate to good reliability (0.53-0.88 and 0.61-0.84, respectively), whereas reliability was good to excellent regarding their average values (0.77-0.95 and 0.81-0.92, respectively). SEM of average peak force and RFD values (4.1-9.4% and 8.2-13.9%, respectively) were lower than that of peak force and RFD values (5.7-13.0% and 10.7-19.1%, respectively). No significant difference was found in bilateral and reciprocal force ratios between dominant and non-dominant leg.

Conclusions: The GroinBar is a reliable tool to assess hip muscle function in athletic populations and could be used for player screening and follow-up.

Keywords: Hip; Muscle function; Reliability; Soccer.