Endurance Training Attenuates Heart Rate Drift When Exercising At The Same Relative Intensity: 1266: Board #29 May 30 11:00 AM - 12:30 PM

Cardiovascular drift is the progressive increase in heart rate (HR) and decrease in stroke volume and arterial blood pressure during prolonged exercise. Animal studies report decreases in HR drift at the same absolute work rate after endurance training. Effects of endurance training on cardiovascular drift at the same relative work rate have not been investigated.

PURPOSE: We tested the hypothesis that endurance training would attenuate cardiovascular drift when exercising at the same relative work intensity.

METHODS: HR, mean arterial pressure (MAP), forearm cutaneous blood flow (CBF; laser-Doppler flowmetry), oxygen uptake (VO2), tympanic temperature, and body weight were recorded in thirteen healthy, young subjects (25±1 yr) at rest and during 40 minutes of cycling at the same relative VO2 (50% VO2peak) before and after 8 weeks of endurance training. Standard deviation of the R-R interval (SDNN) and high frequency power (HF) were calculated from the ECG.

RESULTS: VO2peak increased 17±3% after training (p < 0.01). Training elicited a lower HR at rest and during exercise (p = 0.03). The increase in HR during exercise (i.e., HR drift) was also significantly less after training (p = 0.01). Training had no effect on SDNN and HF during exercise (p = 0.66 and 0.37 respectively). MAP at rest (cuff) and changes during exercise (fnometer) were not significantly different after training (p = 0.25). CBF was not significantly different at rest or during exercise after training (p = 0.902). The loss in body weight during exercise was the same for both trials (δ-0.36 kg before vs. δ-0.45 kg after; p = 0.1).

CONCLUSIONS: HR drift is diminished after 8 weeks of endurance training despite no apparent changes in cardiovagal activity while exercising at the same relative work intensity.