title: Effects of dynamic stretching on strength, muscle imbalance, and muscle activation.
abstract: OBJECTIVE
  This study aimed to examine the acute effects of dynamic stretching on concentric leg extensor and flexor peak torque, eccentric leg flexor peak torque, and the conventional and functional hamstring-quadriceps (H:Q) ratios.
  
  
  METHODS
  Twenty-one women (mean ± SD age = 20.6 ± 2.0 yr, body mass = 64.5 ± 9.3 kg, height = 164.7 ± 6.5 cm) performed maximal voluntary isokinetic leg extension, flexion, and eccentric hamstring muscle actions at the angular velocities of 60°·s and 180°·s before and after a bout of dynamic hamstring and quadriceps stretching as well as a control condition.
  
  
  RESULTS
  Leg flexion peak torque decreased under both control (mean ± SE for 60°s = 75.8 ± 4.0 to 72.4 ± 3.7 N·m, 180°·s = 62.1 ± 3.2 to 59.1 ± 3.1 N·m) and stretching (60°·s = 73.1 ± 3.9 to 65.8 ± 3.3 N·m, 180°·s = 61.2 ± 3.3 to 54.7 ± 2.6 N·m) conditions, whereas eccentric hamstring peak torque decreased only after the stretching (60°·s = 87.3 ± 5.1 to 73.3 ± 3.6 N·m, 180°·s = 89.2 ± 4.4 to 77.0 ± 3.4 N·m) intervention (P ≤ 0.05). Stretching also caused a decrease in conventional H:Q (60°·s = 0.58 ± 0.02 to 0.54 ± 0.02, 180°·s = 0.67 ± 0.02 to 0.61 ± 0.03) and functional H:Q ratios (60°·s = 0.69 ± 0.03 to 0.60 ± 0.03, 180°·s = 1.00 ± 0.06 to 0.60 ± 0.03) (P ≤ 0.05).
  
  
  CONCLUSIONS
  Because dynamic stretching reduced concentric and eccentric hamstring strength as well as the conventional and functional H:Q ratios, fitness and allied-health professionals may need to be cautious when recommending dynamic rather than static stretching to maintain muscle force.
authors.affiliation: 1Human Performance Laboratory, Department of Kinesiology, California State University-San Bernardino, San Bernardino, CA; 2Biomechanics Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, KS; 3Department of Ophthalmology, University of Kansas School of Medicine, Prairie Village, KS; and 4Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE.
authors.forename: Pablo B
authors.initials: PB
authors.lastname: Costa
authors.forename: Trent J
authors.initials: TJ
authors.lastname: Herda
authors.forename: Ashley A
authors.initials: AA
authors.lastname: Herda
authors.forename: Joel T
authors.initials: JT
authors.lastname: Cramer
mesh_terms: D000293:Adolescent; D001265:Athletic Injuries / Q000517:prevention & control; D005260:Female; D006801:Humans; D053580:Muscle Strength / Q000502:physiology*; D052580:Muscle Stretching Exercises / Q000379:methods*; D018482:Muscle, Skeletal / Q000293:injuries / Q000502:physiology; D052097:Quadriceps Muscle / Q000502:physiology; D013848:Thigh / Q000502:physiology; D019415:Torque; D055815:Young Adult