Relationship between oxygen pulse and arteriovenous oxygen difference in healthy subjects: Effect of exercise intensity

Aims: Aims were to assess: (1) the relationships between oxygen pulse and areteriovenous oxygen difference; and (2) the reproducibility of cardiac output and stroke volume values during submaximal and maximal exercises. Methods: Twelve healthy male participated in the study. They were tested on five occasions, separated by periods of 3 days. After tests familiarization, they performed a duplicate progressive maximal exercise on a cycle ergometer to measure maximal oxygen uptake, maximal aerobic power, maximal cardiac output, maximal Stroke Volume and maximal Heart rate. At the fourth and fifth visits, subjects performed two graded submaximal physical exercises. Values collected during duplicated submaximal and maximal exercises were used for the assessment of the reliability of cardiovascular measurements. Results: We found no significant differences between cardiac output and stroke volume values in both first and second trial. All coefficients of variation were under 10% and intra class correlation coefficients values were high than 0.90 during submaximal and maximal exercises. The linear regression analyses indicated high r-squared between oxygen pulse and areteriovenous oxygen difference until 50% of maximal aerobic power. However, at 60% and 100% of maximal aerobic power, this relationship was not found. We found significant increases of stroke volume (P < 0.05) between each two successive bouts from rest until 40% of maximal aerobic power, after that, stroke volume values were stabilized. In contrast, we found a progressive increase of oxygen pulse (P < 0.05) and areteriovenous oxygen difference (P < 0.05) from rest until maximal exercise. Conclusion: Using the impedance device, cardiac output and stroke volume values were reproducible during submaximal and maximal exercises. Oxygen pulse could be a predictor of arteriovenous oxygen difference during submaximal exercise (until 50% of the maximal aerobic power) in healthy subjects.