title: Child-adult differences in the kinetics of torque development.
abstract: Children have lower size-normalised maximal voluntary force, speed, and power than adults. It has been hypothesised that these and other age-related performance differences are due to lesser type-II motor-unit utilisation in children. This should be manifested as slower force kinetics in explosive muscle contractions. The purpose of this study was to investigate the nature of child-adult force-kinetics differences and whether the latter could support that hypothesis. Untrained boys (n = 20) and men (n = 20) (10.1 ± 1.3 and 22.9 ± 4.4 years, respectively), performed maximal, explosive, isometric elbow flexions and knee extensions on a Biodex dynamometer. Peak torque (MVC), times to 10-100% MVC, and other kinetics parameters were determined. The boys' body-mass-normalised knee extension MVC, peak rate of torque development, and %MVC at 100 ms were 26, 17 and 23% lower compared with the men and their times to 30% and 80% MVC were 24 and 48% longer, respectively. Elbow flexion kinetics showed similar or greater differences. The findings illuminate boys' inherent disadvantage in tasks requiring speed or explosive force. It is demonstrated that the extent of the boys-men kinetics disparity cannot be explained by muscle-composition and/or musculo-tendinous-stiffness differences. We suggest therefore that the findings indirectly support children's lower utilisation of type-II motor units.
authors: Faculty of Applied Health Sciences, Brock University, St Catharines, Ontario, Canada. rdotan@brocku.ca
authors: Raffy
authors: R
authors: Dotan
authors: Cameron
authors: C
authors: Mitchell
authors: Rotem
authors: R
authors: Cohen
authors: David
authors: D
authors: Gabriel
authors: Panagiota
authors: P
authors: Klentrou
authors: Bareket
authors: B
authors: Falk
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002648:Child; D004550:Elbow / Q000502:physiology; D004576:Electromyography; D006801:Humans; D007700:Kinetics; D007717:Knee / Q000502:physiology; D008297:Male; D009119:Muscle Contraction; D053580:Muscle Strength / Q000502:physiology; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology*; D019415:Torque; D055815:Young Adult