Carbonated Water Ingestion Increases Blood Pressures And Cerebral Blood Flow Index Post- exercise In The Heat

We previously reported that carbonated water ingestion increased mean arterial pressure and middle cerebral artery mean blood velocity (an index of cerebral blood flow) in resting humans exposed to ambient heat stress (Fujii et al. 2022). However, it is unknown whether similar responses occur after exercise in the heat, which can induce post-exercise hypotension and possibly reduce cerebral blood flow. If carbonated water ingestion increases both arterial blood pressure and cerebral blood flow post-exercise, carbonated water might be a novel countermeasure to attenuate the risks of syncope associated with post-exercise hypotension. PURPOSE: Investigate the effects of carbonated water ingestion on mean arterial pressure and middle cerebral artery mean blood velocity after exercise in the heat. METHOD: Seven healthy, habitually active young adults (1 female) performed cycle exercise for 60 min at 45% of peak oxygen uptake in the heat (35 °C, 50% relative humidity). Participants ingested 150 mL of 4 °C carbonated water at 20 min and 40 min post-exercise. On a separate day, participants ingested 150 mL of 4 °C noncarbonated water as a control. Arterial blood pressure, middle cerebral artery mean blood velocity, heart rate, skin blood flow, sweat rate, rectal temperature, plasma volume and osmolality, thermal perceptions and mood states were measured. RESULT: Participants lost ~2.0% of body weight after exercise. Mean arterial pressure was reduced post-exercise relative to pre-exercise baseline (P < 0.05). Both drinks increased mean arterial pressure from pre-drink baseline; however, carbonated water induced greater increases (9.1 ± 3.6 mmHg vs 3.5 ± 2.7 mmHg at 20 min post-exercise and 5.8 ± 3.2 mmHg vs 2.9 ± 2.8 mmHg at 40 min post-exercise, both P < 0.05). Similarly, both drinks increased middle cerebral artery mean blood velocity from pre-drink baseline but changes were greater with carbonated water (5.5 ± 4.5 cm/s vs 2.0 ± 2.7 cm/s at 20 min post-exercise and 4.0 ± 2.6 cm/s vs 2.2 ± 3.9 cm/s at 40 min post-exercise, both P < 0.05). CONCLUSION: These data suggest that carbonated water ingestion increases mean arterial pressure and cerebral blood flow index after exercise in the heat. Funding: Supported by Asahi Soft Drinks Co. Ltd.