title: Muscle fatigue and metabolic responses following three different antagonist pre-load resistance exercises.
abstract: OBJECTIVE
  Preload of antagonist muscles can be achieved by reciprocal actions (RAs) or by opposing muscle actions. However, evidence concerning neuromuscular and fatigue responses are scarce.
  
  
  OBJECTIVE
  To compare the effects of different knee flexor (KF) preload methods on knee extension (KE) vastus medialis muscle fatigue, based on EMG-spectral index (FI), load range (LR), total work (TW), blood lactate (LAC) and biceps femoris co-activation (BFc) during resistance exercise.
  
  
  METHODS
  Twenty-four healthy men (23.5±3.6yrs) performed three antagonist pre-load isokinetic exercises (4 sets, 10 repetitions, 60°s(-1), 1min rest between sets): RA (KF contraction immediately followed by KE); Superset (SS; one KF set immediately followed by one KE set); Multiple Set (MS; four KF sets followed by four KE sets).
  
  
  RESULTS
  Total work was significantly greater in RA. There was no significant decrease in LR between sets in RA. The BFc did not differ between protocols (p=0.063). However, RA presented greater biceps femoriscoactivation. The FI was greater during SS compared to RA and MS (p<0.05). The SS had greater LAC when compared to MS and RA (p=0.005 and p=0.007, respectively).
  
  
  CONCLUSIONS
  It is suggested that the RA protocol is more neuromuscular and metabolic efficient during the performance of knee extension resistance exercise.
authors.affiliation: Universidade de Brasília (UnB), Brasília, DF, Brazil. rodrigocarregaro@unb.br
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Carregaro
authors.forename: Rafael
authors.initials: R
authors.lastname: Cunha
authors.forename: Carlos Gomes
authors.initials: CG
authors.lastname: Oliveira
authors.forename: Lee E
authors.initials: LE
authors.lastname: Brown
authors.forename: Martim
authors.initials: M
authors.lastname: Bottaro
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D055070:Resistance Training / Q000379:methods*
chemical_list: D019344:Lactic Acid
keywords: Electromyography; Isokinetic; Knee joint; Resistance exercise