Voluntary activation of the triceps surae in prepubertal children.
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.
Grosset
Jean François
JF
Département de Génie Biologique, UMR CNRS - 6600, Université de Technologie, F-60205, Compiègne cedex, France.
Mora
Isabelle
I
Lambertz
Daniel
D
Pérot
Chantal
C
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