title: Electromechanical delay of the knee extensor muscles: comparison among young, middle-age and older individuals.
abstract: The aim of this study was to investigate the effects of the ageing process in the electromechanical delay (EMD), rate of torque development (RTD) and peak torque (PT) of the knee extensor muscles. The volunteers were assigned to three groups: young group (YG - 23·44 ± 4·74 years, 78·14 ± 15·11 kg, 1·72 ± 0·05 m), middle-aged group (MAG - 49·56 ± 6·06 years, 72·01 ± 14·07 kg, 1·67 ± 0·06 m) and elderly group (EG - 68·67 ± 9·06 years, 67·96 ± 7·60 kg, 1·64 ± 0·07 m). The PT and RTD were assessed during maximal voluntary ballistic isometric contractions (MVBIC) in the isokinetic dynamometer. Muscle electrical activity was recorded (EMG) during MVBIC in the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles. The EMD was calculated during the MVBIC, through the time interval between the EMG onset and torque onset. The PT and RTD were higher in the YG than in the MAG (P = 0·02; P = 0·01, respectively) and in the EG (P = 0·002; P = 0·0004, respectively). There were no significant differences in EMD among the three age groups for the VL, VM and RF (P>0·05) muscles. We conclude that age affects the PT and RTD, but not EMD of the VL, VM and RF muscles.
authors.affiliation: Department of Physical Education (DEFMH), Center of Biological and Health Sciences (CCBS), Federal University of São Carlos (UFSCar), São Carlos, Brazil.|Group of Study and Research in Neuromuscular Adaptations to Resistance Training, School of Physical Education and Sports, University of São Paulo-SP, São Paulo, Brazil.|Laboratory of Exercise Physiology, School of Physical Education, State University of Campinas-SP, Campinas, Brazil.
authors.forename: Cleiton A
authors.initials: CA
authors.lastname: Libardi
authors.affiliation: Laboratory of Exercise Physiology, School of Physical Education, State University of Campinas-SP, Campinas, Brazil.
authors.forename: Thiago M F
authors.initials: TM
authors.lastname: Souza
authors.affiliation: Laboratory of Exercise Physiology, School of Physical Education, State University of Campinas-SP, Campinas, Brazil.
authors.forename: Miguel S
authors.initials: MS
authors.lastname: Conceição
authors.affiliation: Laboratory of Exercise Physiology, School of Physical Education, State University of Campinas-SP, Campinas, Brazil.
authors.forename: Valéria
authors.initials: V
authors.lastname: Bonganha
authors.affiliation: Laboratory of Exercise Physiology, School of Physical Education, State University of Campinas-SP, Campinas, Brazil.
authors.forename: Mara Patricia T
authors.initials: MP
authors.lastname: Chacon-Mikahil
authors.affiliation: Laboratory of Exercise Physiology, School of Physical Education, State University of Campinas-SP, Campinas, Brazil.
authors.forename: Cláudia R
authors.initials: CR
authors.lastname: Cavaglieri
authors.affiliation: Laboratory of Electromyographic Studies, School of Physical Education, State University of Campinas-SP, Campinas, Brazil.
authors.forename: Antonio C
authors.initials: AC
authors.lastname: de Moraes
authors.affiliation: Group of Study and Research in Neuromuscular Adaptations to Resistance Training, School of Physical Education and Sports, University of São Paulo-SP, São Paulo, Brazil.
authors.forename: Carlos
authors.initials: C
authors.lastname: Ugrinowitsch
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D004576:Electromyography; D056966:Excitation Contraction Coupling / Q000502:physiology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019415:Torque; D055815:Young Adult
keywords: ballistic; elderly; electromechanical delay; peak torque; rate of torque development