High-intensity exercise significantly prolonged the time constant of oxygen uptake compared with low-intensity exercise (61.2 vs 52.3 seconds, p<0.005) in patients with prior anterior myocardial infarction.
Cross-Sectional (n=23)
No
Does high-intensity exercise compared to low-intensity exercise prolong the time constants of pulmonary gas exchange and heart rate in patients with prior anterior myocardial infarction?
In patients with prior anterior myocardial infarction, gas exchange kinetics are significantly slowed during high-intensity compared to low-intensity exercise, indicating delayed cardiopulmonary adaptation.
Absolute Event Rate: 61.2% vs 52.3%
p-value: p=<0.005
The effect of exercise intensity on gas exchange kinetics was investigated during exercise and recovery, as well as the relationship between the kinetics during exercise and recovery. Twenty-three patients with a history of anterior myocardial infarction performed low-intensity (38.7+/-8.3 W) and high-intensity (68.8+/-15.0 W) exercise for 6 min. The time constants of oxygen uptake (VO2), carbon dioxide output (VCO2) and minute ventilation (VE) were significantly prolonged during high intensity exercise compared with low-intensity exercise (61.2+/-8.6 vs 52.3+/-10.3 s, p<0.005 for the time constant of VO2). The time constant of VO2 was similar during exercise and during recovery from exercise of high (61.2+/-8.6 vs 66.2+/-12.2 s) as well as low intensity (52.3+/-10.3 vs 55.0+/-10.1 s). However, the time constants of VCO2 and heart rate were significantly shorter during recovery than during exercise. The time constants of VCO2 and VE were significantly longer than that of VO2 during both exercise and recovery. In the present study, it was found that (1) the gas exchange kinetics were influenced by the intensity of exercise; (2) the kinetics during recovery did not necessarily reflect the kinetics during exercise except for VO2; and (3) the kinetics of VCO2 and VE were delayed as compared with the VO2 kinetics. These characteristics should be taken into account when using gas exchange kinetics to estimate cardiopulmonary responses to exercise in patients with left ventricular dysfunction.
Shimizu et al. (Fri,) conducted a cross-sectional in Anterior Myocardial Infarction (n=23). High-intensity constant work-rate exercise vs. Low-intensity constant work-rate exercise (38.7±8.3 W) was evaluated on Time constant of oxygen uptake (VO2) during exercise (p=<0.005). High-intensity exercise significantly prolonged the time constant of oxygen uptake compared with low-intensity exercise (61.2 vs 52.3 seconds, p<0.005) in patients with prior anterior myocardial infarction.