title: Hamstring flexibility increases the same with 3 or 9 repetitions of stretching held for a total time of 90 s.
abstract: OBJECTIVE
  To determine if stretching for a constant total time with differing repetition durations and number of repetitions over a 6-week period produced different changes in hamstring flexibility measured by knee extension range of motion (ROM).
  
  
  METHODS
  Randomized Control Trial.
  
  
  METHODS
  University laboratory.
  
  
  METHODS
  34 volunteers, 18-25 years old with tight hamstrings as determined by a greater than 30° loss of knee extension with hip flexed to 90° participated in the study.
  
  
  METHODS
  Change in knee extension ROM was assessed in participants who were randomly assigned to a control, or to a stretching group of either 10 s for 9 repetitions or 30 s for 3 repetitions, for a total stretch time of 90 s. Each group stretched 6 days a week for 6 weeks.
  
  
  RESULTS
  Pre to post stretch comparison indicated both stretching groups were successful in increasing joint ROM (11.6 ± 5.25°-13.4 ± 5.36°) over the control (F = 19.77, p < 0.003). However, there was no significant difference between the stretching groups (p = 0.9).
  
  
  CONCLUSIONS
  Stretching for 6 weeks for total of 90 s showed increased joint ROM regardless of the number of repetitions or the duration of each individual stretch.
authors.affiliation: Brigham Young University, Dept. of Exercise Sciences, Provo, UT 84602, USA. Electronic address: wayne_johnson@byu.edu.
authors.forename: A Wayne
authors.initials: AW
authors.lastname: Johnson
authors.affiliation: Brigham Young University, Dept. of Exercise Sciences, Provo, UT 84602, USA. Electronic address: rike_mitchell@byu.edu.
authors.forename: Ulrike H
authors.initials: UH
authors.lastname: Mitchell
authors.affiliation: Brigham Young University, Dept. of Exercise Sciences, Provo, UT 84602, USA. Electronic address: katohead@gmail.com.
authors.forename: Katie
authors.initials: K
authors.lastname: Meek
authors.affiliation: Brigham Young University, Dept. of Exercise Sciences, Provo, UT 84602, USA. Electronic address: brent_feland@byu.edu.
authors.forename: J Brent
authors.initials: JB
authors.lastname: Feland
mesh_terms: D000293:Adolescent; D000328:Adult; D005080:Exercise Test; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D055815:Young Adult
keywords: Knee range of motion; Stretch duration; Stretch repetition; Stretch tolerance