title: Is muscle power related to running speed with changes of direction?
abstract: BACKGROUND
  The purpose of this study was to identify the relationships between leg muscle power and sprinting speed with changes of direction.
  
  
  METHODS
  
  
  
  METHODS
  the study was designed to describe relationships between physical qualities and a component of sports performance.
  
  
  METHODS
  testing was conducted in an indoor sports hall and a biomechanics laboratory.
  
  
  METHODS
  15 male participants were required to be free of injury and have recent experience competing in sports involving sprints with changes of direction.
  
  
  METHODS
  subjects were timed in 8 m sprints in a straight line and with various changes of direction. They were also tested for bilateral and unilateral leg extensor muscle concentric power output by an isokinetic squat and reactive strength by a drop jump.
  
  
  RESULTS
  The correlations between concentric power and straight sprinting speed were non-significant whereas the relationships between reactive strength and straight speed were statistically significant. Correlations between muscle power and speed while changing direction were generally low and non-significant for concentric leg power with some moderate and significant (p<0.05) coefficients found for reactive strength. The participants who turned faster to one side tended to have a reactive strength dominance in the leg responsible for the push-off action.
  
  
  CONCLUSIONS
  The relationships between leg muscle power and change-of-direction speed were not consistent. Reactive strength as measured by the drop jump appears to have some importance for lateral change-of-direction speed, possibly because of similar push-off actions. It was concluded that reactive strength of the leg extensor muscles has some importance in change-of-direction performance but the other technical and perceptual factors than influence agility performance should also be considered.
authors.affiliation: School of Human Movement and Sport Sciences, University of Ballarat, Ballarat, Victoria, Australia. w.young@ballarat.edu.au
authors.forename: W B
authors.initials: WB
authors.lastname: Young
authors.forename: R
authors.initials: R
authors.lastname: James
authors.forename: I
authors.initials: I
authors.lastname: Montgomery
mesh_terms: D000293:Adolescent; D000328:Adult; D006801:Humans; D007698:Kinesis / Q000502:physiology*; D007866:Leg / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012420:Running / Q000502:physiology*