title: A PHYSICAL EDUCATION-BASED STRETCHING PROGRAM PERFORMED ONCE A WEEK ALSO IMPROVES HAMSTRING EXTENSIBILITY IN SCHOOLCHILDREN: A CLUSTER-RANDOMIZED CONTROLLED TRIAL.
abstract: BACKGROUND
  physical education teachers are required to carry out intervention programs for students to achieve health-enhancing flexibility levels. Unfortunately, to our knowledge, there are no studies examining the effect of a stretching program carried out only once a week on schoolchildren.
  
  
  OBJECTIVE
  the purpose of the present study was to compare the effects of a short-term stretching intervention program performed once and twice a week on hamstring extensibility among schoolchildren in the physical education setting.
  
  
  METHODS
  a sample of 180 high school students aged 12-14 years old was randomly assigned (by natural groups) to a control group, experimental group 1 and experimental group 2. During physical education classes, experimental group students performed a stretching program for eight weeks. The experimental group 1 and 2 performed the stretching program once and twice a week, respectively.
  
  
  RESULTS
  the analysis of variance results showed that the students of both experimental groups improved statistically significantly their hamstring extensibility when compared with the control group students (p < 0.01). Nevertheless, no statistically significant differences between the two experimental groups were found (p > 0.05).
  
  
  CONCLUSIONS
  a short-term stretching program performed only once a week improves hamstring extensibility in schoolchildren. When the stretching program is performed twice a week, the improvement in students'hamstring extensibility is not statistically higher.
authors.affiliation: Department of Physical Education and Sport, University of Granada.. dmayorgavega@gmail.com.
authors.forename: Daniel
authors.initials: D
authors.lastname: Mayorga-Vega
authors.affiliation: Facultad de Ciencias de la Educación, Universidad de Málaga (UMA).. rmerino@uma.es.
authors.forename: Rafael
authors.initials: R
authors.lastname: Merino-Marban
authors.affiliation: Servicio de Deportes, Universidad Pablo de Olavide. Spain.. javi_rh_1903@hotmail.com.
authors.forename: Javier
authors.initials: J
authors.lastname: Real
authors.affiliation: Department of Physical Education and Sport, University of Granada.. jviciana@ugr.es.
authors.forename: Jesús
authors.initials: J
authors.lastname: Viciana
mesh_terms: D000293:Adolescent; D002648:Child; D016000:Cluster Analysis; D005260:Female; D000070633:Hamstring Muscles / Q000502:physiology*; D006801:Humans; D008297:Male; D052580:Muscle Stretching Exercises / Q000379:methods*; D010806:Physical Education and Training / Q000379:methods*; D016059:Range of Motion, Articular; D013334:Students; D016896:Treatment Outcome