Substrate utilization during submaximal exercise in obese and normal-weight women

  • Hilary Granat Steffan
  • Wynne Elliott
  • Wayne C. Miller
  • Bo Fernhall
ORIGINAL ARTICLE

Abstract

In this study we compared substrate use at submaximal intensities of a maximal graded exercise test (GXT) with that derived from equivalent intensities during continuous submaximal steady-state exercise in obese and normal-weight women. Sedentary obese (n = 20, body fat >30%) and normal-weight (n = 15, body fat ≤30%) women performed three treadmill tests with concurrent metabolic measurements. Maximal oxygen consumption (O2max) was determined using the Bruce protocol, followed by two, randomly assigned, continuous 15-min, steady-state exercise bouts, on different days; one bout at 50% and one bout at 75% O2max. Analysis of variance revealed no significant differences between groups for blood lactate or respiratory exchange ratio (R) values at any point during exercise. Therefore, obese and normal-weight group data were combined for subsequent analyses. The R at 50% O2max from the GXT [0.83 (0.01)] was significantly (P < 0.05) lower than at 8 min [0.90 (0.01)] and 15 min [0.89 (0.01)] of steady-state exercise, whereas at 75% O2max, the GXT R [0.96 (0.01)] was similar to that seen at 8 min [0.96 (0.01)] and at 15 min of steady-state exercise [0.93 (0.01)]. Blood lactate values at 50% O2max were similar between the GXT [1.66 (0.10) mM] and steady-state exercise [1.65 (0.09) mM], but at 75% O2max the GXT blood lactate values [2.58 (0.21) mM] were lower than after 15 min of steady-state exercise [4.65 (0.46) mM]. Total exercise fat oxidation was greater at 50% compared to 75% O2max. There was no difference in substrate use between sedentary obese and normal-weight women either at rest or during steady-state exercise at the same relative intensity. Total fat oxidation was greater during low- (50% O2max) compared to high-intensity (75% O2max) exercise. Data from a GXT cannot be used to predict R or substrate utilization values for the purpose of exercise prescription.

Key words Energy expenditure Obesity Carbohydrate and fat oxidation Blood lactate 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Hilary Granat Steffan
    • 1
  • Wynne Elliott
    • 1
  • Wayne C. Miller
    • 1
  • Bo Fernhall
    • 1
  1. 1.Exercise Science Programs, The George Washington University Medical Center, 817 23rd Street N.W., Washington, DC 20052, USAUS

Personalised recommendations