Preserved Exercising Muscle Oxygen Delivery: Demand Matching After High Altitude Acclimatization: Because of or In Spite of Elevated Sympathetic Activation?

Preserved Exercising Muscle Oxygen Delivery: Demand Matching After High Altitude Acclimatization: Because of or In Spite of Elevated Sympathetic Activation? Tschakovsky, Michael; Drouin, Patrick; Forbes, Stacey We read with interest the work by Hansen and colleagues (2022) investigating mechanisms responsible for reduced exercising muscle vasodilatation and blood flow after high altitude acclimatization (HA). In this letter we raise a number of points for the author’s and reader’s consideration, arguing against the conclusion that this study has “found” the purpose of chronic hypoxic induced elevations in sympathetic activity. We offer an alternate explanation consistent with the data, and more consistent with the nature of elevated sympathetic activation in chronic hypoxia. In summary, a different experimental approach is required to tease out whether hypoxia-induced chronic elevation in systemic sympathetic activity is responding to or causing elevated vasodilator activation in exercising muscle. Therefore, whether preserved ΔO2del:Δ ̇O2 in HA is because of or in spite of chronic hypoxia-induced elevations in sympathetic activity remains to be determined. This is the peer reviewed version of the following article: Tschakovsky, M.E., Drouin, P.J. and Forbes, S.P.A. (2022), Preserved exercising muscle oxygen delivery:demand matching after high altitude acclimatization: Because of or in spite of elevated sympathetic activation?. J Physiol. Accepted Author Manuscript. https://doi.org/10.1113/JP283898, which has been published in final form at https://doi.org/10.1113/JP283898. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.