Objective: Cardiovascular drift (CVdrift) is characterized by a continuous, gradual increase in heart rate (HR), following ~10 minutes of moderate-intensity aerobic exercise, despite maintenance of a constant work rate. This has important implications for trials which 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. Utilizing 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: Randomized, prospective study.
Setting: Dose-Response to Exercise in Women clinical exercise trail, The Cooper Institute, Dallas, TX.
Participants: Overweight (BMI 25-43 kg/m2), previously sedentary post-menopausal women (N=326).
Intervention: Treadmill and cycling exercise (30-90 minutes, 3-5 times/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 saw small increases in HR (1-4 bpm; 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.