Measurement of Isokinetic Strength in Prepubertal Males

Abstract

* Supported in part by a grant from Hydra-Fitness Industries, Belton, TX. Twenty-nine prepubertal males ( age = 8.2 +/- 1.3 years) were evaluated for concentric isokinetic strength at the knee, shoulder, and elbow joints, [at the dominant (D) and nondominant (ND) sides]. At each joint, flexion (F) was compared with extension (E) at two speeds of 30 degrees /sec (30) versus 90 degrees /sec (90) over each 10% of the range of motion (ROM). Reliability was estimated between identical motions at the D versus ND side. Results for work at the knee joint indicated slightly higher work output at the ND side (23.5 versus 25.0 joules for D versus ND), significantly higher work output for extension compared to flexion (19.0 versus 29.2 joules for F versus E) and for the slower compared to the faster speed (26.2 versus 21.9 joules for 30 versus 90). At the shoulder joint, extension resulted in significantly greater work compared to flexion (14.2 versus 22.0 joules for F versus E) and the slower speed was associated with significantly greater work (1 9.7 versus 16.7 joules for 30 versus 90). At the elbow joint, the only significant difference observed for work occurred for speed, with the faster speed resulting in greater work (10.8 versus 9.5 joules for 30 versus 90). Analysis for torque scores at each of the three joints revealed that extension resulted in greater torque than flexion, 30 degrees /sec resulted in greater torque than 90 O/sec and that peak torque scores occurred during the first 50% of ROM. Correlations to estimate reliability exceeded r = 0.70 for comparisons of torque and work scores for D versus ND. Age, height, and weight correlated r = 0.50 < r < 0.90 with peak torque during each of the motions. It was concluded that prepubertal males have similar patterns of concentric isokinetic strength measured at the knee, shoulder, and elbow joints compared to adults, because strength was greater during E versus F, for slower versus faster speeds, and during the initial phase of ROM.J Ortho Sports Phys Ther 1988;9(10):345-351.