Sodium bicarbonate reduces ventilation without altering core temperature threshold or sensitivity of hyperthermia-induced hyperventilation in exercising humans
Abstract
Hyperthermia stimulates ventilation (hyperthermia-induced hyperventilation). In exercising humans, once the core temperature reaches ∼37°C, minute ventilation (V̇e) increases linearly with rising core temperature, and the slope of the relation between V̇e and core temperature reflects the sensitivity of the response. We previously reported that sodium bicarbonate ingestion reduces V̇e during prolonged exercise in the heat without affecting the sensitivity of hyperthermia-induced hyperventilation. Here, we hypothesized that reductions in V̇e associated with sodium bicarbonate ingestion reflect elevation of the core temperature threshold for hyperthermia-induced hyperventilation. Thirteen healthy young males ingested sodium bicarbonate (0.3 g/kg body wt) (NaHCO 3 trial) or sodium chloride (0.208 g/kg body wt) (NaCl trial), after which they performed a cycle exercise at 50% of peak oxygen uptake in the heat (35°C and 50% relative humidity) following a pre-cooling. The pre-cooling enabled detection of an esophageal temperature (T es : an index of core temperature) threshold for hyperthermia-induced hyperventilation. The T es thresholds for increases in V̇e were similar between the two trials ( P = 0.514). The slopes relating V̇ E to T es also did not differ between trials ( P = 0.131). However, V̇e was lower in the NaHCO 3 than in the NaCl trial in the range of T es = 36.8-38.4°C ( P = 0.007, main effect of trial). These results suggest that sodium bicarbonate ingestion does not…
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Six of 35 studies stated there were no apparent or significant differences in GIS between conditions.
“Alternatively, six of 35 studies stated there were no apparent or significant differences in GIS between conditions”
From Gastrointestinal Symptoms Associated With Sodium Bicarbonate Supplementation Protocols: A Systematic Review (2026) · cites this paper as Katagiri et al. 2023
Remaining delivery modes included sachets, oblates, and edible film wrap.
“Remaining delivery modes included sachets (Guimarães et al. 2020), oblates (Katagiri et al. 2023), and edible film wrap (Katagiri et al. 2024).”
From Gastrointestinal Symptoms Associated With Sodium Bicarbonate Supplementation Protocols: A Systematic Review (2026) · cites this paper as Katagiri et al. 2023
The greater GIS with placebo may be related to the composition of the placebo, which has in other studies shown non-zero presence of GIS.
“possibly related to the composition of the placebo, which has in other studies shown non‐zero presence of GIS”
From Gastrointestinal Symptoms Associated With Sodium Bicarbonate Supplementation Protocols: A Systematic Review (2026) · cites this paper as Katagiri et al. 2023
In one of the six studies reporting no differences, only three participants had GIS assessed.
“in one of these six studies, only three participants had GIS assessed”
From Gastrointestinal Symptoms Associated With Sodium Bicarbonate Supplementation Protocols: A Systematic Review (2026) · cites this paper as Katagiri et al. 2023
In that study, statistical power was extremely low.
“meaning statistical power was extremely low”
From Gastrointestinal Symptoms Associated With Sodium Bicarbonate Supplementation Protocols: A Systematic Review (2026) · cites this paper as Katagiri et al. 2023
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Prolonged exercise shifts ventilatory parameters at the moderate-to-heavy intensity transition
Stevenson, J. D., Kilding, A. E., Plews, D. J., & Maunder, E. (2023) · European Journal of Applied Physiology · doi:10.1007/s00421-023-05285-2 · Cited by 13 · see citing works
Peel, J., McNarry, M. A., Heffernan, S. M., Nevola, V. R., Kilduff, L. P., & Waldron, M. (2025) · American Journal of Physiology-Regulatory, Integrative and Comparative Physiology · doi:10.1152/ajpregu.00186.2024 · Cited by 6 · see citing works
Masoud, A. A., Li, Z., Deyhle, M. R., Siegler, J., Specht, J., McKenna, Z. J., Mermier, C., & Amorim, F. (2025) · European Journal of Applied Physiology · doi:10.1007/s00421-025-05850-x · Cited by 6 · see citing works
Katagiri, A., Fujii, N., Dobashi, K., Lai, Y.-F., Tsuji, B., & Nishiyasu, T. (2024) · American Journal of Physiology-Regulatory, Integrative and Comparative Physiology · doi:10.1152/ajpregu.00161.2024 · Cited by 4 · see citing works
Self-citationWinter, I. P., Sarac, P., & Wilson, P. B. (2026) · European Journal of Sport Science · doi:10.1002/ejsc.70225
- Authors
- Katagiri, A., Fujii, N., Dobashi, K., Lai, Y.-F., Tsuji, B., & Nishiyasu, T.
- Affiliations
- University of Tsukuba (JP)
- Hokkaido University of Education (JP)
- Prefectural University of Hiroshima (JP)
- Venue
- American Journal of Physiology-Regulatory, Integrative and Comparative Physiology
- Publisher
- American Physiological Society
- Published
- 2023-05-15
- Volume
- 325
- Issue
- 1
- Pages
- R69-R80
- ISSN
- 0363-6119 (ISSN-L)
- 1522-1490
- OpenAlex
- W4376612059
- Cited by
- 6
- References
- 0
- Citations by year
- 2026: 1 · 2025: 2 · 2024: 2 · 2023: 1
- FWCI
- 1.07
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- American Journal of Physiology-Regulatory, Integrative and Comparative Physiology (publishedVersion)
- PubMed (publishedVersion)
- Funders
- Ministry of Education, Culture, Sports, Science and Technology (22H00499)
- MEXT | Japan Science and Technology Agency (JPMJSP2124)
- Topics
- Health Sciences › Medicine › Physiology › Thermoregulation and physiological responses
- Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
- Health Sciences › Medicine › Orthopedics and Sports Medicine › Sports Performance and Training
- Keywords
- sodium bicarbonate ingestion, exercise hyperpnea, esophageal temperature, precooling, heat stress
- MeSH terms
- Hyperthermia, Body Temperature, Body Temperature Regulation, Humans, Hyperthermia, Induced, Hyperventilation, Male, Respiration, Sodium Chloride, Temperature, Sodium Bicarbonate
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