Is the ventilatory threshold coincident with maximal fat oxidation during submaximal exercise in women?
BACKGROUND
The purpose of this study was to detect the fraction of peak oxygen consumption (VO2peak) that elicits maximal rates of fat oxidation during submaximal treadmill exercise. It was hypothesized that this point would appear at a work rate just below the ventilatory threshold.


METHODS



METHODS
subjects completed a protocol requiring them to exercise for 15 min on a treadmill at six different workloads, 25, 40, 55, 65, 75, and 85% VO2peak, over two separate visits.


METHODS
nine healthy, moderately-trained eumenorrheic females (age = 28.8+/-5.99 yrs, VO2peak = 47.20 +/-2.57 ml x kg(-1) x min(-1)) volunteered for the study.


METHODS
a one-way ANOVA with repeated measures was used to test for differences across exercise intensities in the metabolic variables (i.e. substrate oxidation, blood lactate concentration ([La-]), RER, and the contribution of fat to total energy expenditure). Following significant F ratios, post-hoc tests were used to detect differences between the means for various exercise intensities.


RESULTS
Exercise at 75% VO2peak elicited the greatest rate of fat oxidation (4.75+/-0.49 kcal x min(-1)), and this intensity was coincident with the ventilatory threshold (76+/-7.41% VO2peak). Moreover, a significant difference (t(8) = -3.98, p<0.01) was noted between the mean ventilatory threshold and lactate threshold.


CONCLUSIONS
The finding that a relatively heavy work rate elicits the highest rate of fat oxidation in an active, female population has application in exercise prescription and refutes the belief that low-intensity exercise is preferred for fat metabolism.
Astorino
T A
TA
Center for Exercise and Applied Human Physiology, University of New Mexico, Albuquerque 87131-1251, USA. mrtodda@unm.edu
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D000704:Analysis of Variance; D050260:Carbohydrate Metabolism; D002245:Carbon Dioxide / Q000097:blood; D004734:Energy Metabolism / Q000502:physiology; D005080:Exercise Test; D005260:Female; D006801:Humans; D007773:Lactates / Q000097:blood; D050356:Lipid Metabolism; D008066:Lipolysis / Q000502:physiology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology; D012420:Running / Q000502:physiology*
D007773:Lactates; D002245:Carbon Dioxide; D010100:Oxygen