Purpose: Biomechanical measures quantified during dynamic tasks with coupled epidemiological data in longitudinal experimental designs may be useful to determine which mechanisms underlie injury risk in young athletes. A key component is the ability to reliably measure biomechanical variables between testing sessions. The purpose was to determine the reliability of three-dimensional (3D) lower-extremity kinematic and kinetic variables during landing in young athletes measured within a session and between two sessions 7 wk apart.
Methods: Lower-extremity kinetics and kinematics were quantified during a drop vertical jump. Coefficient of multiple correlations (CMC), intraclass correlation coefficients (ICC (3, k), ICC (3, 1)), and typical error (TE) analyses were used to examine within- and between-session reliability.
Results: There were no differences in within-session reliability for peak angular rotations between planes with all discrete variables combined (sagittal ICC ≥ 0.933, frontal ICC ≥ 0.955, transverse ICC ≥ 0.934). Similarly, the between-session reliability of kinematic measures were not different between the three planes of motion but were lower than the within-session ICC. The within- and between-session reliability of discrete joint moment variables were excellent for all sagittal (within ICC ≥ 0.925, between ICC ≥ 0.800) and frontal plane moment measures (within ICC ≥ 0.778, between ICC ≥ 0.748). CMC analysis revealed similar averaged within-session (CMC = 0.830 ± 0.119) and between-session (CMC = 0.823 ± 0.124) waveform comparisons.
Conclusion: The majority of the kinematic and kinetic variables in young athletes during landing have excellent to good reliability. The ability to reliably quantify lower-extremity biomechanical variables of young athletes during dynamic tasks over extended intervals may aid in identifying potential mechanisms related to injury risk factors.
1Cincinnati Children's Hospital Medical Center, Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, OH; 2University of Kentucky, Department of Kinesiology and Health Promotion and Biodynamics Laboratory, Lexington, KY; 3University of Cincinnati, College of Medicine, Departments of Pediatrics and Orthopaedic Surgery and Biomedical Engineering, Cincinnati, OH; and 4Rocky Mountain University of Health Professions, Graduate Program in Athletic Training, Provo, UT
Address for correspondence: Kevin R. Ford, M.S., Cincinnati Children's Hospital, 3333 Burnet Avenue; MLC 10001, Cincinnati, OH 45229;E-mail: firstname.lastname@example.org.
Submitted for publication September 2006.
Accepted for publication June 2007.