Abstract
The reproducibility of day-to-day testing of isokinetic concentric and eccentric muscular actions among adolescent basketball players aged 14 to 16 years and relationships of mean within-subject variation in two isokinetic testing sessions with chronological age, biological maturation (estimated age at peak height velocity), training experience, body size, lower-body morphology, and initial strength performance were evaluated. The sample included 27 basketball players who completed replicate test sessions of 5 repetitions of reciprocal concentric and eccentric knee extensions and flexions at 60º s(-1). A randomly selected subsample of 8 players completed a third testing session to confirm reliability estimates. Coefficients of variation (CV) between sessions 1 and 2 ranged from 8.1% to 17.4%, and intraclass coefficients (ICCs) ranged from 0.72 to 0.89. For sessions 1 and 3, CVs ranged from 3.9% to 6.0%, and ICCs ranged from 0.95 to 0.99. The initial level of strength of eccentric knee flexion (r=-0.43) and eccentric knee extension (r=-0.42) were correlated (P<0.05) with eccentric knee extension within-variation between two sessions. Training experience (r=-0.37, P<0.05) and initial values of concentric knee flexion (r=-0.62, P<0.01) were correlated with concentric knee flexion within-subject differences. Within-subject variation of eccentric knee extension was correlated (P<0.05) with chronologic age (r=0.41), estimated age at peak height velocity (r=-0.38), body size (r=0.41 to 0.47), and leg volume (r=0.39). Familiarization sessions may improve the reliability of concentric and eccentric knee isokinetic strength testing at 60º s(-1) in adolescent basketball players. Age, maturity status, and training experience of young athletes should be considered when testing knee isokinetic strength at 60º s(-1).
Highlights
Isokinetic dynamometry is generally considered the best protocol of dynamic strength measurements [1]
It is suggested that coefficients of variation (CV) should not be greater than ±6.1%, and intraclass correlations (ICC) should be greater than 0.88 [3]
Reliability of the protocols is important as it provides an indication of the biological and technical variation associated with assessment procedures and conditions [13]
Summary
Isokinetic dynamometry is generally considered the best protocol of dynamic strength measurements [1]. The literature suggests inconsistency in the application of isokinetic measurement protocols, which may hinder data interpretation [2]. Valid isokinetic data require reliable assessment techniques for the peak moment of force, mean peak moment of force, and angle at peak moment of force. The magnitude of measurement error in isokinetic testing in general and in particular with young athletes has not been systematically addressed. Young athletes are a highly select group with regard to skill, performance, size, and physique; variation in maturity status is an additional factor affecting growth in size and function especially during adolescence [6, 7]
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