title: Voluntary activation of the triceps surae in prepubertal children.
abstract: The activation capacities and neuromuscular efficiency (NME) of the triceps surae (TS) of prepubescent children (7-11 years) and adults were evaluated during submaximal and maximal (MVC) isometric plantarflexion to determine whether they varied with age. TS-EMG were obtained by summing-up the rectified electromyograms of the soleus and gastrocnemii muscles; these data were quantified using a sliding average method and normalized with reference to the TS maximal compound action potential (TS-M-wave). The maximal EMG increased significantly with age in the children, but less than MVC, what led to a significant increase in NME(Max) (MVC/TS-EMG(max) ratio). The EMG-torque relationship indicated an age-related overactivation of TS at low torque, what led to a lower NME(Sub-max) (inverse of the slope of the EMG-torque relationship) for the youngest children. The overactivation of TS was accompanied by contraction of the TA, which decreased with age. The youngest children were also less able to maintain a target torque and muscle activation. Finally, the twitch interpolated method revealed an age-dependant activation deficit. We conclude that central mechanisms are the main cause of the lower torques developed by children and they appear to vary with age in prepubertal children.
authors.affiliation: Département de Génie Biologique, UMR CNRS - 6600, Université de Technologie, F-60205, Compiègne cedex, France.
authors.forename: Jean François
authors.initials: JF
authors.lastname: Grosset
authors.forename: Isabelle
authors.initials: I
authors.lastname: Mora
authors.forename: Daniel
authors.initials: D
authors.lastname: Lambertz
authors.forename: Chantal
authors.initials: C
authors.lastname: Pérot
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000367:Age Factors; D000843:Ankle Joint / Q000502:physiology; D001827:Body Height; D001835:Body Weight; D002648:Child; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D016552:Ergometry / Q000379:methods; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011627:Puberty / Q000502:physiology; D012016:Reference Values; D019415:Torque