The anaerobic threshold during exercise-based cardiac rehabilitation

Abstract

Summary The purposes of this study were (a) to examine the concept of an anaerobic threshold (AT) based upon a change in the slope of blood lactate (BL) and the volume of expired air (E) during incremental exercise, (b) to examine the relationship between BL and E, and (c) to establish the level of AT in terms of the percentage of peak oxygen uptake (%O 2pk ) for post myocardial infarction patients (PMIP). Thirty-two male recent non-blockade PMIP, aged 60.2±6.2 years, performed a graded exercise test on a motorized treadmill until volitional cessation or reaching any of the American College of Sports Medicine (ACSM) criteria. Oxygen uptake and E were recorded every 30 seconds during the exercise. Blood lactate was measured before, during exercise (at the end of each stage) and in recovery for the third and the sixth minute. The results showed that the inflection point for both BL and E in relation to %O 2pk was easily determined and corresponded to 72% and 70% respectively. A correlation of 0.93 ( P 2pk . The results provided evidence that 70%O 2pk represents the mean onset of metabolic acidosis, an undesirable intensity of exercise for cardiac rehabilitation. Health professionals, unable to measure oxygen uptake, can monitor respiratory changes and use these as a valuable indicator of aerobic limits during exercise. This will assist in setting a programme that maximizes the training benefits whilst minimizing the risk.