title: The association of intensity and overall level of physical activity energy expenditure with a marker of insulin resistance.
abstract: OBJECTIVE
  Physical activity is important in preventing insulin resistance, but it is unclear which dimension of activity confers this benefit. We examined the association of overall level and intensity of physical activity with fasting insulin level, a marker of insulin resistance.
  
  
  METHODS
  This was a cross-sectional analysis of the Medical Research Council Ely population-based cohort study (2000--2002). Physical activity energy expenditure (PAEE) in kJ kg(-1) min(-1) was measured by heart rate monitoring with individual calibration over a period of 4 days. The percentage of time spent above 1.5, 1.75 and 2 times resting heart rate (RHR) represented all light-to-vigorous, moderate-to-vigorous and vigorous activity, respectively.
  
  
  RESULTS
  Data from a total of 643 non-diabetic individuals (319 men, 324 women) aged 50 to 75 years were analysed. In multivariate linear regression analyses, adjusting for age, sex and body fat percentage, PAEE was significantly associated with fasting insulin (pmol/l) (beta = -0.875, p = 0.006). Time (% of total) spent above 1.75 x RHR and also time spent above 2 x RHR were both significantly associated with fasting insulin (beta = -0.0109, p = 0.007 and beta = -0.0365, p = 0.001 respectively), after adjusting for PAEE, age, sex and body fat percentage. Time spent above 1.5 x RHR was not significantly associated with fasting insulin in a similar model (beta = -0.0026, p = 0.137).
  
  
  CONCLUSIONS
  The association between PAEE and fasting insulin level, a marker of insulin resistance, may be attributable to the time spent in moderate-to-vigorous and vigorous activity, but not to time spent in light-intensity physical activity.
authors.affiliation: MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Box 285, Hills Road, Cambridge, CB2 0QQ, UK.
authors.forename: F K
authors.initials: FK
authors.lastname: Assah
authors.forename: S
authors.initials: S
authors.lastname: Brage
authors.forename: U
authors.initials: U
authors.lastname: Ekelund
authors.forename: N J
authors.initials: NJ
authors.lastname: Wareham
mesh_terms: D000368:Aged; D015415:Biomarkers; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology / Q000209:etiology; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D006339:Heart Rate; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011446:Prospective Studies
chemical_list: D015415:Biomarkers