Performance Nutrition & Thermoregulation
HUMAN PERFORMANCE & THE ENVIRONMENT
Overview
We conduct and are involved in a broad range of research and community outreach projects that encompass nutritional support for endurance exercise, metabolic buffering and supplementation, recovery strategies to support exercise performance, and strategies to mitigate heat stress. A number of our projects in this area are also in close collaboration with the ASU Athleat Field Lab directed by Dr Floris Wardennar and the Hydration Science Lab directed by Dr Stavros Kavouras, as well as Dr Jenni Vanos in the School of Sustainability.
Current Projects
Sodium bicarbonate supplementation & heat stress mitigation
Sodium bicarbonate supplementation, often used to offset the deleterious metabolic effects of intense exercise, has been widely researched in various capacities since the early 1900’s. Briefly, the kidneys produce the molecule bicarbonate (HCO3-), which in turn tightly regulates acid-base balance in the body and ultimately provides a “first line of defense” during high rates of metabolic flux (e.g., exertional, high intensity work or exercise). Although more commonly used in athletic scenarios to improve exercise performance, we’ve begun a series of investigations focused alternate uses of the supplement that are focused on potential thermoregulatory and renal benefits during prolonged physical activity in the heat.
Anthocyanins & exercise in hot environments
Anthocyanin, a type of polyphenol, is found abundantly in berries (e.g., New Zealand blackcurrant) and is the pigment responsible for coloring those that are blue and purple. In recent years, research has focused on anthocyanin’s efficacy as antioxidants and potential to promote health outcomes by reducing systemic inflammation. We have begun a line of research focused on exploring optimal dosing strategies, as well as investigating the effects anthocyanins may have on gut permeability during exercise in the heat.
Alkalosis and perception of effort
During prolonged, high-intensity exercise, muscles can produce an excess of hydrogen ions (H+), which results in metabolic disturbances and may ultimately contribute to fatigue. Blood bicarbonate facilitates the removal of these H+ ions, and to a certain extent, supports the body’s ability to meet the high rates of energy demand required to maintain muscle contractile function during such activity. The afferent III/IV group fibers are sensitive to the level of acidosis in the blood and signal the brain to up- or downregulate the motor neural input (cycling power output) to the active muscles. This project investigates whether supplementing sodium bicarbonate affects the afferent feedback (represented by the perception of effort) across the full spectrum of exercise intensity (from light to hard) using a clamped-RPE approach by altering blood acidosis. Additionally, we are examining the mechanisms in the afferent feedback loop (EMG, muscle and brain oxygenation, lactate, gas exchange, and pain levels) to understand the possible effect on the perception of effort.
Relevant Publications, Conferences & Media
Publications
Freire, R, Neimanas, N, Wardenaar, F, Guardaro, M and Vanos, J. et al. Heat stress symptoms & cooling center efficacy among older adults experiencing homelessness in Phoenix, Arizona. Environ. Res.: Health 3 035009 (2025). https://doi.org/10.1088/2752-5309/ae050f
Freire, R., Schott, K.D., Butterick, B. et al. A 3D color model reports urine color similarly to a printed color chart with similar accuracy to determine a low vs. high urine concentration. Perform. Nutr. 1, 8 (2025). https://doi.org/10.1186/s44410-025-00009-3.
Gray, E., Cavaleri, R. Siegler, J. Mouth rinsing and ingesting unpleasant salty or bitter solutions, after heavy intensity cycling, does not influence sprint performance or knee extensor force in trained cyclists. Int J Sports Physiol Perform. 20(2): 232-237, 2025 (doi: 10.1123/ijspp.2023-0314).
Gurton, W.H., King, D.G., Ranchoras, M.K., Siegler, J.C., Gough, L.A. Oral but not topical sodium bicarbonate improves repeated sprint performance during simulated soccer match play exercise in collegiate athletes. Int J Sport Nutr Exerc Metab. 34(6): 362-371, 2024 (doi: 10.1123/ijsnem.2024-0059).
Wardenaar, F.C., Whitenack, L., Vento, K.A., Seltzer, R.G.N., Siegler, J., Kavouras, S.A. Validity of combined hydration self-assessment measurements to estimate a low vs. high urine concentration in a small sample of (tactical) athletes. Eur J Nutr. 63(1): 185-193, 2024. 2023 (doi: 10.1007/s00394-023-03254-1).
Rose, C., McGuire, H., Graham, K., Siegler, J., Fazekas de St Groth, B., Caillaud, C., Edwards, K. Partial body cryotherapy exposure drives acute redistribution of circulating lymphocytes: preliminary findings. Eur J Appl Phyisol. 123(2), 407-415, 2023 (doi: 10.1007/s00421-022-05058-3)
Siegler, J.C., Carr, A., Jardine, W., Convit, L., Cross, R., Chapman, D., Burke, L.M., Ross, M. The hyperhydration potential of sodium bicarbonate and sodium citrate. Int J Sport Nutr Exerc Metab. 32(2): 74-81, 2022 (doi: 10.1123/ijsnem.2021-0179).
Wardenaar, F., Armistead, S., Boeckman, K., Butterick, B., Youssefi, D., Thompsett, D., & Vento, K. Validity of Urine Color Scoring Using Different Light Conditions and Scoring Techniques to Assess Urine Concentration. J Athl Train, 57(2), 191– 198, 2022 (doi: 10.4085/1062-6050-0389.21.).
Conference Presentations
2025 Exploring the efficacy of sodium bicarbonate supplementation on reducing markers of acute injury (AKI) during physical work in the heat; European College of Sports Science Annual Congress - Rimini, IT
2025 Exploring the efficacy of sodium bicarbonate supplementation on reducing markers of acute injury (AKI) during physical work in the heat; Arizona State University Digital Health Summit - Phoenix, AZ
2024 Exploring the efficacy of sodium bicarbonate supplementation on reducing markers of acute injury (AKI) during physical work in the heat; Southwest American College of Sports Medicine Annual Conference - Irvine, CA
2024 Facilitating remote assessment: verbal guidence enhances precision in self-measured body circumference; American Sport and Performance Dietitians Association Annual Conference - Kansas City, MO
2024 Validation of a new standard for the assessment of body composition and metabolic function: a pilot study; European College of Sport Science Annual Meeting - Glasgow, UK
2024 Beating the heat with sodium bicarbonate supplementation: a thermoregulatory strategy to improve physical performance; Southwest American College of Sports Medicine (SACSM) Annual Meeting – Irvine, CA
2024 Myth Busters in Sports Nutrition; American College of Sports Medicine (ACSM) Annual Meeting – PINES Special Interest Group, Boston, MA
2023 Exploring the use of ischemic preconditioning prior to exercise after spinal cord injury: a pilot - American College of Sports Medicine Annual Meeting - Denver, CO
2023 Timing of nordic hamstring exercise in youth soccer players to reduce injury; Southwest American College of Sports Medicine Annual Meeting - Costa Mesa, CA
2023 Timing of nordic hamstring exercise in youth soccer players to reduce injury; Institute for Social Science Research Student Symposium at Arizona State University - Phoenix, AZ
2023 Myth Busters in Sports Nutrition; American College of Sports Medicine (ACSM) Annual Meeting – PINES Special Interest Group, Denver, CO
2022 Integration of buffering agents into hyperhydration strategies prior to competing in the heat; European College of Sport Science (ECSS) Annual Meeting – Sports Nutrition Special Interest Group, Sevilla, ESP
2021 The efficacy of combining sodium bicarbonate and glycerol ingestion for the purposes of hyperhydration; American College of Sports Medicine Annual Meeting, Online (Thematic poster)
Media
This common kitchen ingredient is giving elite athletes a boost - August 2024 The Show KJZZ NPR
Baking soda and other tips for Olympians - or everyday athletes - July 2024 ASU News
Pat’s Run - April 2024 ASU News
The pill that over half the distance medallists used at the 2023 Worlds (Letsrun.com)