Background: Yoga is a popular exercise, but the heart rate (HR) response to specific styles of yoga is unknown. Primary Study Objective: To determine if vinyasa yoga is an aerobic physical activity based on the HR response of participants. Methods/Design: Observational study using a convenience sample Setting: Exercise room on a university campus Participants: Forty-two adults aged 21-54 years with prior yoga experience completed the yoga session with no adverse events. Equipment malfunction precluded data analysis for 4 participants. Intervention: A 50-minute vinyasa yoga class that included 10 minutes of pre-activity rest, 35 minutes of asanas, and 5 minutes of meditation. Participant HR was recorded continuously during the class. Primary Outcome Measures: Mean HR response and time spent at each intensity level during asanas. Results: The data of 38 participants were analyzed. Mean (SD) HR for all participants during asanas was 107 (23) beats per minute (bpm), and 44% of the asana time was considered light-intensity aerobic physical activity. The mean response (expressed as a percent of maximal HR or %HRmax) was considered very light intensity (<50% of HRmax) for 6 participants, light intensity (50-63% of HRmax) for 21 participants, moderate intensity (64-76% of HRmax) for 10 participants, and vigorous intensity (77-93% of HRmax) for 1 participant. Conclusions: In the current study, vinyasa yoga was primarily a light-intensity aerobic physical activity, but individual responses varied. This information adds to the body of literature regarding the physiological response to yoga and specifically addresses the aerobic response to vinyasa yoga.