Evaluation of heart rate as a method for assessing moderate intensity physical activity.
To further develop our understanding of the relationship between habitual physical activity and health, research studies require a method of assessment that is objective, accurate, and noninvasive. Heart rate (HR) monitoring represents a promising tool for measurement because it is a physiological parameter that correlates well with energy expenditure (EE). However, one of the limitations of HR monitoring is that training state and individual HR characteristics can affect the HR-VO2 relationship.


OBJECTIVE
The primary purpose of this study was to examine the relationship between HR (beats x min(-1)) and VO2 (mL x kg(-1 x -1) min(-1)) during field- and laboratory-based moderate-intensity activities. In addition, we examined the validity of estimating EE from HR after adjusting for age and fitness. This was done by expressing the data as a percent of heart rate reserve (%HRR) and percent of VO2 reserve (%VO2R).


METHODS
Sixty-one adults (18-74 yr) performed physical tasks in both a laboratory and field setting. HR and VO2 were measured continuously during the 15-min tasks. Mean values over min 5-15 were used to perform linear regression analysis on HR versus VO2. HR data were then used to predict EE (METs), using age-predicted HRmax and estimated VO2max.


RESULTS
The correlation between HR and VO2 was r = 0.68, with HR accounting for 47% of the variability in VO2. After adjusting for age and fitness level, HR was an accurate predictor of EE (r = 0.87, SEE = 0.76 METs).


CONCLUSIONS
This method of analyzing HR data could allow researchers to more accurately quantify physical activity in free-living individuals.
Strath
S J
SJ
Department of Exercise Science and Sport Management, University of Tennessee, Knoxville 37996, USA. sstrath@utk.edu
Swartz
A M
AM
Bassett
D R
DR
O'Brien
W L
WL
King
G A
GA
Ainsworth
B E
BE
D000328:Adult; D000368:Aged; D004734:Energy Metabolism; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D018670:Monitoring, Ambulatory; D010101:Oxygen Consumption; D010809:Physical Fitness; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity