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Heart rate and exercise intensity during training: observations from the DREW Study
  1. C R Mikus1,
  2. C P Earnest1,
  3. S N Blair2,
  4. T S Church1
  1. 1
    Preventive Medicine Laboratory, Pennington Biomedical Research Center, Baton Rouge, Louisiana, USA
  2. 2
    Arnold School of Public Health, University of South Carolina, Columbia, South Carolina, USA
  1. Correspondence to Dr Timothy S Church, Preventive Medicine Laboratory, Pennington Biomedical Research Center, 6400 Perkins Rd, Baton Rouge, LA 70808, USA; tim.church{at}pbrc.edu

Abstract

Objective: Cardiovascular drift (CVdrift) is characterised by a continuous, gradual increase in heart rate (HR) after ∼10 min of moderate-intensity aerobic exercise, despite maintenance of a constant work rate. This has important implications for trials that employ HR to monitor exercise intensity, as reducing work rate in order to keep HR constant could result in participants exercising below the intended intensity. Utilising the Dose Response to Exercise in Women (DREW) database, we sought to determine if increases in HR during exercise (CVdrift) resulted in clinically significant reductions in exercise work rate in order to keep HR within a target range.

Design: Randomised, prospective study.

Setting: DREW clinical exercise trail, The Cooper Institute, Dallas, Texas.

Participants: Overweight (body mass index 25–43 kg/m2), previously sedentary postmenopausal women (n  =  326).

Intervention: Treadmill and cycling exercise (30–90 min, three to five times per week) at a HR corresponding to 50% of peak oxygen uptake (Vo2peak).

Main outcome measure: Changes in exercise intensity (metabolic equivalents (METS)) during exercise in response to CVdrift.

Results: We observed small increases in HR (1–4 beats per minute, p<0.001) combined with small increases in intensity (0.01–0.03 METS, p<0.03) during the combined 12 963 exercise training sessions. Further, we identified only 101 (0.78%) sessions in which intensity was reduced during the course of the exercise session, potentially in response to CVdrift.

Conclusions: We conclude that CVdrift did not contribute to significant reductions in exercise intensity in the DREW study.

https://doi.org/10.1136/bjsm.2008.046342

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    Footnotes

    • Funding Grant HL66262 from the National Institutes of Health.

    • Competing interests Declared. TSC reports having received honoraria for lectures from scientific, educational and community groups; serving as a consultant for Trestle Tree; and having a book in publication from which he will receive royalties. SNB reports receiving book royalties from Human Kinetics; honoraria for service on the Medical Advisory Boards for Matria Health Care, Magellan Health Services and Jenny Craig; and honoraria for lectures from scientific, educational and community groups. SNB also reports that he is paid as an executive lecturer by the University of North Texas. He gives these fees to the University of South Carolina Educational Foundation or to other nonprofit groups, and he reports that during the past 5-year period, he has received a research grant from Jenny Craig. CPE reports having received honoraria for lectures from scientific, educational and community groups.