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Concurrent adaptations in maximal aerobic capacity, heat tolerance, microvascular blood flow and oxygen extraction following heat acclimation and ischemic preconditioning

Lookup NU author(s): Dr Owen JeffriesORCiD

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Abstract

We investigated the effects of: 1) Ischemic pre-conditioning (IPC) plus a concurrent five-day heat acclimation + IPC (IPC+HA), 2) five-day HA with sham IPC (HA), or 3) control (CON) on thermoneutral measurements of endurance performance, resting measures of skeletal muscle oxygenation and blood flow. Twenty-nine participants were randomly allocated to three groups, which included: 1) five-days of repeated leg occlusion (4 x 5-min) IPC at limb occlusive pressure, plus fixed-intensity (55% O_2max) cycling HA at ~36°C/40% humidity; 2) HA plus sham IPC (20 mmHg) or 3) or CON (thermoneutral 55% O_2max plus sham IPC). In IPC+HA and HA, there were increases in maximal oxygen consumption ( O_2max) (7.8% and 5.4%, respectively; P < 0.05), ventilatory threshold (V_T) (5.6% and 2.4%, respectively, P < 0.05), delta efficiency (DE) (2.0% and 1.4%, respectively; P < 0.05) and maximum oxygen pulse (O₂pulse-Max) (7.0% and 6.9%, respectively; P < 0.05) during an exhaustive incremental test. There were no changes for CON (P > 0.05). Changes (P < 0.05) in resting core temperature (T_C), muscle oxygen consumption (mO₂), and limb blood flow (LBF) were also found pre-to-post intervention among the HA and IPC+HA groups, but not in CON (P > 0.05). Five-days of either HA or IPC+HA can enhance markers of endurance performance in cooler environments, alongside improved muscle oxygen extraction, blood flow, exercising muscle efficiency and O₂ pulse at higher intensities, thus suggesting the occurrence of peripheral adaptation. Both HA and IPC+HA enhance the adaptation of endurance capacity, which might partly relate to peripheral changes.

Publication metadata

Author(s): Waldron M, Papavasileiou G, Jeffries O, Nevola V, Heffernan SM, Kilduff L, Tallent J

Publication type: Article

Publication status: Published

Journal: Journal of Thermal Biology

Year: 2020

Volume: 93

Print publication date: 01/10/2020

Online publication date: 08/09/2020

Acceptance date: 28/08/2020

Date deposited: 23/10/2020

ISSN (print): 0306-4565

ISSN (electronic): 1879-0992

Publisher: Elsevier Ltd

URL: https://doi.org/10.1016/j.jtherbio.2020.102724

DOI: 10.1016/j.jtherbio.2020.102724

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