Cardiovascular Drift (CD) is a physiological phenomenon in which heart rate and VO2 increase in order to maintain cardiac output as the exercise intensity remains the same. Current understanding of CD indicates that CD is caused by a loss of fluids in combination with a reduced ventricular filling time. Different exercise modalities, such as steady state exercise (SSE) and high intensity interval exercise (HIIE) stress the cardiovascular system differently and cause different adaptations. Currently, no research has been conducted observing components (VO2, HR, and RER) of CD in SSE and HIIE. PURPOSE: To determine if HIIE or SSE alters physiological components of CD in healthy aerobically fit individuals. METHODS: Seven aerobically fit individuals (Age 38.14±16.9 yrs.; Ht 172.21 ±10.1 cm.; Wt 72 ± 12.9 kg.; BF% 20.7 ±7.4; VO2 38.79 ± 10.6 ml/kg/min-1) completed a randomized crossover design which consisted of 45 minutes of SSE and HIIE treadmill running to observe differences in VO2, HR, and RER. Participants completed a sing VO2 max ramp protocol treadmill test, which was used to calculate 70%, 90%, and 40% of VO2 reserve (VO2R). The SSE session consisted of 45 minutes of treadmill running at 70% VO2R. The HIIE session consisted of nine 5-minute stages of 3 minutes at 90% VO2R and 2 minutes at 40% VO2R. Data was analyzed via 2 (condition) x 10 (time) repeated measures ANOVA and paired sample t-tests to determine changes in VO2, heart rate (HR), and respiratory exchange ratio (RER). All analyses were performed using SPSS (v.29.01). RESULTS: Significant differences were observed for VO2 between conditions (p=.005), time (p< .001), and condition by time (p <.001). Additionally, HR demonstrated significance between time (p<.001). RER did not have any significant differences between conditions. CONCLUSION: There are significant differences in VO2 values between exercise modalities. Subsequently, as time progressed there were significant differences in VO2 and HR between exercise conditions. Only VO2 had significant differences in time and condition. These differences indicate that different exercise modalities of equal workload elicit varying oxygen utilization, resulting in a drift in oxygen consumption.



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