title: Circuit weight training in cardiac patients: determining optimal workloads for safety and energy expenditure.
abstract: BACKGROUND
  While most studies suggest circuit weight training (CWT) to be safe in cardiac rehabilitation populations, few investigators have controlled variables known to impact CWT intensity. Therefore, the purposes of this study were to determine the energy cost and evaluate safety of cardiac patients while varying rest interval duration and lifting load in a CWT format.
  
  
  METHODS
  Nine male subjects with documented coronary artery disease had maximal oxygen uptake (VO2max), one-repetition maximum (1-RM), and body composition tested. In random order and on separate days, 4 CWT sessions using either 40% or 60% of the 1-RM, and either 30 or 60 seconds of rest between stations were completed. Energy cost, heart rate (HR), blood pressure (BP), and rate-pressure product (RPP) were measured. Data were analyzed with a repeated measures analysis of variance, and Tukey's post-hoc test was performed when significant results were found. The alpha level was set at < .05.
  
  
  RESULTS
  Subjects exercised at 25% to 32% of VO2max (58%-67% of HRmax) during CWT. The HR and RPP responses were lower during all CWT protocols than at 85% of the treadmill VO2max. No subject displayed any ST-segment depression or angina during CWT. The 40%-60-second protocol had an energy cost (2.98 kcal/min) that was lower (P < .05) than the other protocols (3.48-3.81 kcal/min). Increasing the lifting load resulted in increases (P < .05) in energy cost, and decreasing the rest interval increased energy cost only during the 40% 1-RM protocols.
  
  
  CONCLUSIONS
  Results indicate that CWT protocols of varied intensity are safe for cardiac patients when compared to treadmill exercise, and changes in rest interval duration and load can impact the energy cost.
authors.affiliation: University of New Hampshire, Department of Kinesiology, Exercise Physiology Laboratory, Durham 03824, USA.
authors.forename: D W
authors.initials: DW
authors.lastname: DeGroot
authors.forename: T J
authors.initials: TJ
authors.lastname: Quinn
authors.forename: R
authors.initials: R
authors.lastname: Kertzer
authors.forename: N B
authors.initials: NB
authors.lastname: Vroman
authors.forename: W B
authors.initials: WB
authors.lastname: Olney
mesh_terms: D000368:Aged; D003327:Coronary Disease / Q000378:metabolism / Q000503:physiopathology / Q000534:rehabilitation*; D004562:Electrocardiography; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000592:standards; D005500:Follow-Up Studies; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D012449:Safety; D016896:Treatment Outcome; D014891:Weight Lifting / Q000592:standards*; D016526:Workload / Q000592:standards*