Subject: RE: HR Zones and Cardiac Drift I agree with RPE being more important than HR once drift takes place. However, with increased fitness, cardiac drift not only takes longer to occur, but also is reduced to less of an increase than the 10-15bpm that you're experiencing. This has to do with the increased blood volume that your body has as fitness is increased coupled with larger ventricles in the heart and stronger heart. All these things combined allow the heart to pump more blood per stroke because of the larger ventricles and stronger muscles in the heart and the larger blood volume allows the heart to beat less to pump the blood required by then muscles. |