title: The acute effects of performing drop jumps of different intensities on concentric squat strength.
abstract: OBJECTIVE
  To investigate the acute effects of performing drop jumps of different intensities on subsequent squat 1 repetition maximum (1RM).
  
  
  METHODS
  14 participants with strength training experience completed two familiarization sessions to become accustomed with the testing procedures and 1RM-like loads. Following this, four different 1RM testing sessions were completed. In each testing session subjects performed a 5-min bicycle warm-up followed by a series of sets with increasingly heavier loads until squat 1RM was achieved. During the first of these four sessions squat 1RM was assessed without the addition of drop jumps to the 1RM warm-up routine, thus was designated the control (CTRL) condition. In the final 3 testing sessions, two drop jumps from either 30 (DJ30), 45 (DJ45), or 60 (DJ60) cm were added to the warm-up routine that preceded squat 1RM assessment. EMG activity of the vastus lateralis was also monitored during 1RM testing.
  
  
  RESULTS
  Squat 1RM without prior plyometric activity was 128.4±36.1 kg. Following DJ30, DJ45, and DJ60 squat 1RM equaled 130.4±36.4 kg, 130.9±38.3 kg, 131.0±38.9 kg, respectively. A repeated measures ANOVA uncovered a significant main effect of warm-up condition (P=0.021). Post hoc analysis revealed that differences in the 1RM values were only significant between DJ30 and CTRL (P=0.002). No significant differences in muscle activation of the vastus lateralis were noted between the conditions.
  
  
  CONCLUSIONS
  These findings indicate lower body strength in individuals familiar with resistance training can be acutely enhanced when preceded by a warm-up incorporating a low volume of low intensity drop jumps.
authors.affiliation: Department of Kinesiology and Physical Education, University of the Fraser Valley, Abbotsford, BC, Canada. jason.brandenburg@ufv.ca
authors.forename: J
authors.initials: J
authors.lastname: Brandenburg
authors.forename: A
authors.initials: A
authors.lastname: Czajka
mesh_terms: D000704:Analysis of Variance; D004576:Electromyography; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D010806:Physical Education and Training; D055070:Resistance Training; D055815:Young Adult