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Sodium bicarbonate reduces ventilation without altering core temperature threshold or sensitivity of hyperthermia-induced hyperventilation in exercising humans.

Authors :
Katagiri A
Fujii N
Dobashi K
Lai YF
Tsuji B
Nishiyasu T
Source :
American journal of physiology. Regulatory, integrative and comparative physiology [Am J Physiol Regul Integr Comp Physiol] 2023 Jul 01; Vol. 325 (1), pp. R69-R80. Date of Electronic Publication: 2023 May 15.
Publication Year :
2023

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 <subscript>3</subscript> 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 <subscript>es</subscript> : an index of core temperature) threshold for hyperthermia-induced hyperventilation. The T <subscript>es</subscript> thresholds for increases in V̇e were similar between the two trials ( P = 0.514). The slopes relating V̇ <subscript>E</subscript> to T <subscript>es</subscript> also did not differ between trials ( P = 0.131). However, V̇e was lower in the NaHCO <subscript>3</subscript> than in the NaCl trial in the range of T <subscript>es</subscript> = 36.8-38.4°C ( P = 0.007, main effect of trial). These results suggest that sodium bicarbonate ingestion does not alter the core temperature threshold or sensitivity of hyperthermia-induced hyperventilation during prolonged exercise in the heat; instead, it downshifts the exercise hyperpnea.

Details

Language :
English
ISSN :
1522-1490
Volume :
325
Issue :
1
Database :
MEDLINE
Journal :
American journal of physiology. Regulatory, integrative and comparative physiology
Publication Type :
Academic Journal
Accession number :
37184224
Full Text :
https://doi.org/10.1152/ajpregu.00282.2022