VO₂ Reserve vs. Heart Rate Reserve During Moderate Intensity Treadmill Exercise

VO₂ and heart rate (HR) are widely used when determining appropriate training intensities for clinical, healthy, and athletic populations. It has been shown that if the % reserve (%R) is used, rather than % of max, HR and VO₂ can be used interchangeably to accurately prescribe exercise intensities. Thus, heart rate reserve (HRR) can be prescribed if VO₂ reserve (VO₂R) is known. Therefore, the purpose of this study was to compare VO₂ R and HRR during moderate intensity exercise (50%R). Physically active college students performed a maximal treadmill test to exhaustion. During which VO₂ and HR were monitored to determine max values. Upon completion of the maximal test, calculations were made to determine the % grade expected to yield approximately 50% of the subjects VO₂R. Subjects then returned to complete the submaximal test (50%R) at least two days later. The %VO₂R and %HRR were calculated and compared to the predicted value as well as to each other. Statistical analysis revealed that VO₂ at 50%R was significantly greater than the actual VO₂ achieved, p < .001. Conversely, the mean predicted HR at 50%R was significantly less than the actual HR achieved, p < .001. In conclusion, this study indicated that VO₂ could be more accurately predicted than HR during moderate intensity exercise. The weak correlation between VO₂R and HRR indicates that caution should be used when relying on a HR to determine VO₂.