Reliability of unfamiliar, multijoint, uni- and bilateral strength tests: effects of load and laterality

To better understand the reliability of unfamiliar multijoint strength tests, 16 resistance-trained men performed maximum velocity uni- (1 leg [1L]) and bilateral (2 legs [2L]) lifts on an unfamiliar semiprone leg squat machine with loads equivalent to 40 and 70% of maximum isometric force on 2 separate occasions. Peak force was highly reproducible between testing occasions at the heavy load under both uni- and bilateral conditions (intraclass correlation coefficient [ICC](1L70%) = 0.91, ICC(2L70%) = 0.92), was slightly reduced in the light load bilateral condition (ICC(2L40%) = 0.85), and was significantly (p < 0.05) reduced in the light load unilateral condition (ICC(1L40%) = 0.57). Test reliability was not related to total load lifted (2L 70% > 1L 70% > 2L 40% > 1L 40%) or to the peak force developed during the tests (2L 70% > 1L 70% = 2L 40% > 1L 40%), but it was somewhat related to the time taken to attain peak force (2L 70% = 1L 70% > 2L 40% > 1L 40%). To obtain reliable strength data from athletes, more familiarization seems to be needed when they perform modified versions of common multijoint strength tests, or unfamiliar strength tests, under light load, unilateral conditions. The marked differences in reliability resulting from variation in loading conditions suggests that the reliability of a test needs to be reestablished when it is modified, before it is used to assess athlete/subject strength performance.