title: Strength training and physical activity in boys: a randomized trial.
abstract: BACKGROUND
  In developed societies levels of daily physical activity (PA) among school-age children are decreasing. This implies risk factors for cardiovascular and metabolic diseases. Specific strategies to improve levels of PA are needed. In prepubertal boys there is evidence that strength training increases spontaneous PA outside of training.
  
  
  METHODS
  A total of 102 schoolchildren (age 10-14 years) in Switzerland were randomly assigned to physical education classes or to participate twice weekly at a guided strength training program for 19 weeks. Spontaneous PA energy expenditure (PAEE; 3axial accelerometry for 7 days), leg and arm strength, and body composition (dual energy radiograph absorptiometry) were measured at baseline, after 19 weeks of training intervention, and after 3 months of washout.
  
  
  RESULTS
  There were no significant differences between the groups at baseline. In the intervention group, PAEE increased by 10% from baseline to end of training in boys (P = .02), but not in girls. Leg and arm strength were increased owing to training intervention in both boys and girls. All other variables were unchanged. Baseline PAEE was significantly negatively correlated with changes of PAEE.
  
  
  CONCLUSIONS
  Targeted strength training significantly increases daily spontaneous PA behavior in boys. The less active children showed the greatest increase in spontaneous PAEE. Girls showed a similar increase in strength, but not in spontaneous PAEE. This may be explained by their earlier pubertal development. Strength training may be a promising strategy in schools to counteract decreasing levels of PA.
authors.affiliation: Head of the Center for Pediatric Endocrinology Zurich, Moehrlistrasse 69, CH-8006 Zurich, Switzerland. urs.eiholzer@pezz.ch.
authors.forename: Udo
authors.initials: U
authors.lastname: Meinhardt
authors.forename: Fabienne
authors.initials: F
authors.lastname: Witassek
authors.forename: Renato
authors.initials: R
authors.lastname: Petrò
authors.forename: Chris
authors.initials: C
authors.lastname: Fritz
authors.forename: Urs
authors.initials: U
authors.lastname: Eiholzer
mesh_terms: D015502:Absorptiometry, Photon; D061725:Accelerometry; D000293:Adolescent; D001823:Body Composition; D002648:Child; D002652:Child Behavior / Q000502:physiology*; D004734:Energy Metabolism; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007899:Leisure Activities; D008297:Male; D009043:Motor Activity / Q000502:physiology; D053580:Muscle Strength; D010806:Physical Education and Training; D012044:Regression Analysis; D055070:Resistance Training / Q000379:methods*; D012574:Schools; D012737:Sex Factors; D013557:Switzerland
keywords: children; puberty; spontaneous physical activity; strength training