title: Muscle group specific changes in the electromechanical delay following short-term resistance training.
abstract: OBJECTIVE
  The time delay between the onset of a muscle's electrical activity and force is believed to have important functional implications, and has been shown to decrease following resistance training in males. The purpose of this investigation was to examine changes in the voluntary electromechanical delay (EMD) for the leg extensors and flexors following a short-term resistance training intervention in females.
  
  
  METHODS
  Pretest/posttest control group experiment.
  
  
  METHODS
  Twenty-two previously untrained females (mean±SD age=21±2 years; mass=65.4±13.3kg) were randomly assigned to training (n=10) and control (n=12) groups. The training group performed barbell back squats and deadlifts twice per week for four weeks. EMD for the vastus lateralis (extensors) and biceps femoris (flexors) was examined during maximal voluntary contractions at pre- and posttesting. Data were examined using analyses of covariance (ANCOVAs) with the pretest and posttest scores serving as the covariate and dependent variable, respectively, and by evaluating the number of participants that exceeded the minimal difference statistic.
  
  
  RESULTS
  For the leg extensors, the adjusted EMD posttest mean for the training group was significantly lower than that for the control group (74.3 vs. 91.8ms; p=0.015; ή(2)=0.275), and five training participants displayed decreases that exceeded the minimal difference. The ANCOVA for the leg flexors was not significant (adjusted means=98.0 vs. 90.0ms; p=0.487; ή(2)=.026).
  
  
  CONCLUSIONS
  Four weeks of multi-joint resistance training resulted in decreased EMD for the leg extensors, but not the flexors.
authors.affiliation: Human Performance Laboratory, Department of Kinesiology and Sport Management, Texas Tech University, USA. Electronic address: matt.stock@ttu.edu.
authors.forename: Matt S
authors.initials: MS
authors.lastname: Stock
authors.affiliation: Human Performance Laboratory, Department of Kinesiology and Sport Management, Texas Tech University, USA.
authors.forename: Kendra D
authors.initials: KD
authors.lastname: Olinghouse
authors.affiliation: Human Performance Laboratory, Department of Kinesiology and Sport Management, Texas Tech University, USA.
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Mota
authors.affiliation: Human Performance Laboratory, Department of Kinesiology and Sport Management, Texas Tech University, USA.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Drusch
authors.affiliation: Neuromuscular Research Laboratory, Health, Physical Education, and Recreation, Utah State University, USA.
authors.forename: Brennan J
authors.initials: BJ
authors.lastname: Thompson
mesh_terms: D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D005260:Female; D000070633:Hamstring Muscles / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D011897:Random Allocation; D015203:Reproducibility of Results; D055070:Resistance Training / Q000379:methods*; D019415:Torque; D055815:Young Adult
keywords: Biceps femoris; Force; Motor unit; Torque; Vastus lateralis