Abstract:

Objectives: During an incremental exercise test, increased metabolic demands of exercising muscle should be compensated with increased O2 uptake and heart rate until to their maximal levels. Anaerobic threshold (AT) describes the point of metabolic transition from aerobic to anaerobic metabolism and reflect moderate exercise intensity. The aim of this study was to evaluate O2 uptake to heart beat ratio (O2 pulse) and heat rate to work rate ratio (HR/WR) in response to constant load exercise at work load corresponded to AT. Method: Twelve healthy young male subjects initially performed an incremental exercise test (15 W/min) until exhaustion. Then, each subject performed a 30 min of constant load exercise test that work load at their AT on separate days. Pulmonary gas exchange parameters were measured breath-by breath using a metabolic gas analyser. Cardiac parameters were followed continuously beat-by beat using a 12 lead ECG. AT estimated non-invasively using V-slope method. Results: The heart rate for each watt of work production (HR/WR) was ranged between 0.97 beat/min/W to 1.76 beat/min/W and averaged 1.25±0.2 beat/min/W. The O2 pulse was ranged between 10.56 mL/min/beat to 16.15 mL/min/beat and averaged 13.38±1.5 mL/min/beat at the end of the test. A negative statistically significant correlation (R = - 0.90316, p<0.0001) between HR/WR and O2 pulse values were observed. In addition, a negative statistically significant correlation (R = - 0.67621, p<0.01) were observed between O2 uptake for each kg of body weight reflecting fitness status of subjects and O2 pulse values. Conclusion: Increased heartbeat for each watt of work production is conversely related with the fitness status of subjects. Measurements of O2 pulse and HR/WR during aerobic exercise can provide valuable information with regarding subject’s fitness status. Investigators should be considering moderate intensity aerobic exercise instead of using incremental exercise that contains aerobic and anaerobic work production.

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