title: Do stiffness and asymmetries predict change of direction performance?
abstract: Change of direction speed (CODS) underpins performance in a wide range of sports but little is known about how stiffness and asymmetries affect CODS. Eighteen healthy males performed unilateral drop jumps to determine vertical, ankle, knee and hip stiffness, and a CODS test to evaluate left and right leg cutting performance during which ground reaction force data were sampled. A step-wise regression analysis was performed to ascertain the determinants of CODS time. A two-variable regression model explained 63% (R2= 0.63; P = 0.001) of CODS performance. The model included the mean vertical stiffness and jump height asymmetry determined during the drop jump. Faster athletes (n = 9) exhibited greater vertical stiffness (F = 12.40; P = 0.001) and less asymmetry in drop jump height (F = 6.02; P = 0.026) than slower athletes (n  = 9); effect sizes were both "large" in magnitude. Results suggest that overall vertical stiffness and drop jump height asymmetry are the strongest predictors of CODS in a healthy, non-athletic population.
authors.affiliation: a Institute of Sports Science and Physical Activity Research , University of Bedfordshire , Bedford , UK.
authors.forename: Sean J
authors.initials: SJ
authors.lastname: Maloney
authors.affiliation: a Institute of Sports Science and Physical Activity Research , University of Bedfordshire , Bedford , UK.
authors.forename: Joanna
authors.initials: J
authors.lastname: Richards
authors.affiliation: a Institute of Sports Science and Physical Activity Research , University of Bedfordshire , Bedford , UK.
authors.forename: Daniel G D
authors.initials: DG
authors.lastname: Nixon
authors.affiliation: a Institute of Sports Science and Physical Activity Research , University of Bedfordshire , Bedford , UK.
authors.forename: Lewis J
authors.initials: LJ
authors.lastname: Harvey
authors.affiliation: a Institute of Sports Science and Physical Activity Research , University of Bedfordshire , Bedford , UK.
authors.forename: Iain M
authors.initials: IM
authors.lastname: Fletcher
mesh_terms: D000842:Ankle / Q000502:physiology; D000886:Anthropometry; D001696:Biomechanical Phenomena; D006615:Hip / Q000502:physiology; D006801:Humans; D007717:Knee / Q000502:physiology; D007866:Leg / Q000502:physiology; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D009048:Motor Skills / Q000502:physiology*; D009068:Movement; D018482:Muscle, Skeletal / Q000502:physiology*; D059385:Plyometric Exercise; D012044:Regression Analysis; D055815:Young Adult
keywords: Agility; cutting; leg-spring behaviour; spring-mass model; torsional spring model