title: Effect of exercise intensity on post-exercise oxygen consumption and heart rate recovery.
abstract: OBJECTIVE
  There is some evidence that measures of acute post-exercise recovery are sensitive to the homeostatic stress of the preceding exercise and these measurements warrant further investigation as possible markers of training load. The current study investigated which of four different measures of metabolic and autonomic recovery was most sensitive to changes in exercise intensity.
  
  
  METHODS
  Thirty-eight moderately trained runners completed 20-min bouts of treadmill exercise at 60, 70 and 80% of maximal oxygen uptake (VO2max) and four different recovery measurements were determined: the magnitude of excess post-exercise oxygen consumption (EPOCMAG), the time constant of the oxygen consumption recovery curve (EPOCτ), heart rate recovery within 1 min (HRR60s) and the time constant of the heart rate recovery curve (HRRτ) .
  
  
  RESULTS
  Despite significant differences in exercise parameters at each exercise intensity, only EPOCMAG showed significantly slower recovery with each increase in exercise intensity at the group level and in the majority of individuals. EPOCτ was significantly slower at 70 and 80% of VO₂max vs. 60% VO₂max and HRRτ was only significantly slower when comparing the 80 vs. 60% VO₂max exercise bouts. In contrast, HRR60s reflected faster recovery at 70 and 80% of VO₂max than at 60% VO₂max.
  
  
  CONCLUSIONS
  Of the four recovery measurements investigated, EPOCMAG was the most sensitive to changes in exercise intensity and shows potential to reflect changes in the homeostatic stress of exercise at the group and individual level. Determining EPOCMAG may help to interpret the homeostatic stress of laboratory-based research trials or training sessions.
authors.affiliation: UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Newlands, PO BOX 115, Cape Town, 7725, South Africa, theresa.mann@gmail.com.
authors.forename: Theresa N
authors.initials: TN
authors.lastname: Mann
authors.forename: Christopher
authors.initials: C
authors.lastname: Webster
authors.forename: Robert P
authors.initials: RP
authors.lastname: Lamberts
authors.forename: Michael I
authors.initials: MI
authors.lastname: Lambert
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D020127:Recovery of Function