title: Does aerobic exercise improve or impair cardiorespiratory fitness and health among cleaners? A cluster randomized controlled trial.
abstract: OBJECTIVE
  It is unknown if aerobic exercise overloads or improves the cardiovascular system among workers with high occupational physical activity. This was investigated in a worksite randomized controlled trial (RCT) of aerobic exercise among cleaners.
  
  
  METHODS
  We randomized 116 cleaners between 18-65 years. The aerobic exercise group (N=57) performed worksite aerobic exercise (30 minutes twice a week) and the reference group (N=59) received lectures. Cardiorespiratory fitness, blood pressure (BP) and diurnal heart rate (HR) for measuring aerobic workload [% HR reserve (% HRR)] were collected at baseline and after four months. A repeated measure 2×2 multi-adjusted mixed-model design was applied to compare the between-group differences in an intention-to-treat analysis.
  
  
  RESULTS
  Between-group differences (P<0.01) were found: cardiorespiratory fitness 2.2 [standard error (SE) 0.8] ml O 2 × min -1 × kg -1 [95% confidence interval (95% CI) 0.6-3.8], aerobic workload - 3.5 (SE 1.2) % HRR (95% CI - 5.9- -1.0), resting HR -3.8 (SE 1.2) bpm (95 % CI -6.1- - 1.4), sleeping HR -3.8 (SE 1.1) bpm (95% CI - 5.9- - 1.7), and systolic BP 3.6 (SE 1.3) mmHg (95% CI 1.1-6.0).
  
  
  CONCLUSIONS
  Worksite aerobic exercise seems to improve cardiorespiratory fitness, aerobic workload, and resting and sleeping HR, but increase systolic BP among cleaners. Beneficial physiological cardiovascular effects are seen from aerobic exercise, but also a harmful effect is evident. Therefore, recommendations should take into consideration the potential cardiovascular overload from additional aerobic exercise on workers with high levels of occupational physical activity.
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen Ø, Denmark. mkl@nrcwe.dk.
authors.forename: Mette
authors.initials: M
authors.lastname: Korshøj
authors.forename: Mark
authors.initials: M
authors.lastname: Lidegaard
authors.forename: Jørgen H
authors.initials: JH
authors.lastname: Skotte
authors.forename: Peter
authors.initials: P
authors.lastname: Krustrup
authors.forename: Niklas
authors.initials: N
authors.lastname: Krause
authors.forename: Karen
authors.initials: K
authors.lastname: Søgaard
authors.forename: Andreas
authors.initials: A
authors.lastname: Holtermann
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006796:Household Work; D006801:Humans; D008875:Middle Aged; D016272:Occupational Health; D012143:Respiratory Physiological Phenomena; D055815:Young Adult