The purpose of the study was to determine how an aerobic moderate intensity (AE/mod) versus an anaerobic high intensity interval training (AnE/HIIT) intervention affected plasma volume and VO2max in sedentary individuals. METHODS: Subjects were 11 sedentary males and females (21 ± 1.3 yr) who were randomly divided into two groups. The AE/mod group consisted of five subjects and the AnE/HITT group consisted of six subjects. Each subject attended a pre- and post-intervention session where a VO2peak test was completed on a cycle ergometer and resting blood samples were collected via capillary puncture for plasma volume analysis. Between testing, the subjects completed a three week exercise intervention on stationary cycle ergometers. During each session, the AE/mod group cycled for 20 min at 60-70% of W at VO2peak. The AnE/HIIT group completed intervals of 30 s at 80-90% of W at VO2peak with rest periods of 120 s at 35-45% of W at VO2peak. Both groups had a total work time of 30 min which included a 5 min warm up and cool down at 40-50% of W at VO2peak. RESULTS: No significant differences were found between the pre- and post-testing in plasma volume or VO2peak for the AE/mod or AnE/HIIT group. CONCLUSION: The researchers suggest that a reason no significant differences were found was due to the length of the intervention. The study could set a foundation for future researchers to examine how plasma volume and VO2peak are affected by different exercise interventions in sedentary individuals utilizing a longer intervention.