Mechanisms Underlying Hypoxic, Heat and Cross-tolerance Adaptation in Women
NCT Number: NCT06575985
Acronym: FemAdapt_HOT
Status: NOT_YET_RECRUITING
Study Type: INTERVENTIONAL
Phases: NA
Conditions: Heat Exposure|Exercise Training
Interventions: OTHER: Heat acclimation and exercise training|OTHER: Thermo-neutral exercise training group
Sponsor: Jozef Stefan Institute
Collaborators: University of Ljubljana|University of Ljubljana, Faculty of Medicine
Sex: FEMALE
Age: ADULT
Enrollment: 30
Study Design: Allocation: RANDOMIZED|Intervention Model: PARALLEL|Masking: SINGLE (OUTCOMES_ASSESSOR)|Primary Purpose: BASIC_SCIENCE
Start Date: 2024-10
Completion Date: 2024-12
Locations: Jozef Stefan Institute, Ljubljana, SI, 1000, Slovenia|University of Ljubljana, Ljubljana, 1000, Slovenia

Summary:
This study will consist of a parallel-groups design, with 30 healthy active female participants randomly assigned to either an experimental heat acclimation and exercise intervention, or a thermo-neutral exercise intervention control group. Interventions will be 10 days in duration, and consist of daily 60-minute exercise bouts under the appropriate environmental condition. Before and after each intervention, various tests will be conducted to establish exercise capacity under various environmental conditions, as well as underlying mechanisms of physiological adaptation induced by each intervention.

Primary Outcome Measures: Exercise capacity under thermo-neutral normoxic conditions, Results of an incremental exercise test to exhaustion conducted at 23°C and an FiO2 of 0.209, quantified using maximal oxygen uptake, Measured once before (pre) and once up to 1 week after (post) the intervention period|Exercise capacity under hot normoxic conditions, Results of an incremental exercise test to exhaustion conducted at 35°C and an FiO2 of 0.209, quantified using maximal oxygen uptake, Measured once before (pre) and once up to 1 week after (post) the intervention period|Exercise capacity under thermo-neutral hypoxic conditions, Results of an incremental exercise test to exhaustion conducted at 23°C and an FiO2 of 0.135, quantified using maximal oxygen uptake, Measured once before (pre) and once up to 1 week after (post) the intervention period
Secondary Outcome Measures: Core body temperature regulation during exercise, Core body temperature measured throughout the incremental exercise tests using a rectal temperature probe., Measured once before (pre) and once up to 1 week after (post) the intervention period|Skin temperature regulation during exercise, Skin temperature measured throughout the incremental exercise tests using temperature probes attached to the calf, thigh, chest and arm, from which weighted averages are calculated., Measured once before (pre) and once up to 1 week after (post) the intervention period|Sweat rates during exercise, Sweat rate measured throughout the incremental exercise tests using a sensor attached to the forehead., Measured once before (pre) and once up to 1 week after (post) the intervention period|Hemo-dynamic activity during exercise, Cardiac output measured throughout the incremental exercise tests by bio-electrical impedance cardiography., Measured once before (pre) and once up to 1 week after (post) the intervention period|Pulmonary ventilation during exercise, Pulmonary ventilation measured throughout the incremental exercise tests using flow measurements as recorded by metabolic cart., Measured once before (pre) and once up to 1 week after (post) the intervention period|Gas exchange during exercise, Balance of oxygen uptake and carbon dioxide production measured throughout the incremental exercise tests using gas composition sensors recorded by metabolic cart., Measured once before (pre) and once up to 1 week after (post) the intervention period|Muscle oxygenation during exercise, Vastus lateralis oxygenation measured throughout the incremental exercise tests using near-infrared spectroscopy., Measured once before (pre) and once up to 1 week after (post) the intervention period|Brain oxygenation during exercise, Cerebral oxygenation measured at the left pre-frontal cortex throughout the incremental exercise tests using near-infrared spectroscopy., Measured once before (pre) and once up to 1 week after (post) the intervention period|Pulse oxygen saturation during exercise, Capillary oxygen saturation measured on the right earlobe throughout the incremental exercise tests using pulse oximetry., Measured once before (pre) and once up to 1 week after (post) the intervention period|Body composition, Body mass measured using standard weighing scales, with body fat percentage estimated using a standardized eight-site skinfold measurement protocol with associated equation., Measured once before (pre) and once up to 1 week after (post) the intervention period|Lung function, Standard spirometry procedure to assess lung function using forced expiratory volume, Measured once before (pre) and once up to 1 week after (post) the intervention period|Hemoglobin mass, Hemoglobin mass estimation using the carbon monoxide re-breathing method, Measured once before (pre) and once up to 1 week after (post) the intervention period|Blood/plasma volume, Blood/plasma volume estimation using the carbon monoxide re-breathing method, Measured once before (pre) and once up to 1 week after (post) the intervention period|Skeletal muscle mitochondrial function, Skeletal muscle mitochondrial function quantified using a peripheral vascular occlusion test, with the rate of decrease in muscle oxygenation used to estimate mitochondrial function., Measured once before (pre) and once up to 1 week after (post) the intervention period|Skeletal muscle vascular responsiveness, Skeletal muscle vascular responsiveness quantified using a peripheral vascular occlusion test, with the rate of increase in muscle oxygenation during re-perfusion, and the oxygenation overshoot relative to pre-occlusion baseline, used to estimate vascular responsiveness., Measured once before (pre) and once up to 1 week after (post) the intervention period|Blood viscosity, Blood viscosity will be measured by obtaining venous blood samples from the participants, extracting plasma, and using a cone/plate viscometer to quantify viscosity and varying shear rates., Measured once before (pre) and once up to 1 week after (post) the intervention period|Oxidative stress marker, Venous blood samples will be obtained to quantify redox balance from the extracted plasma., Measured once before (pre) and once up to 1 week after (post) the intervention period|Hematopoiesis, Venous blood samples will be obtained to measure various markers of hematopoiesis from the extracted plasma, serum and/or whole blood., Measured once before (pre) and once up to 1 week after (post) the intervention period|Heat shock proteins, Venous blood samples will be obtained to measure heat shock proteins in the extracted plasma and serum., Measured once before (pre) and once up to 1 week after (post) the intervention period|Hypoxia-inducible factor 1α, Venous blood samples will be obtained to measure hypoxia-inducible factor 1α in the extracted plasma and serum., Measured once before (pre) and once up to 1 week after (post) the intervention period
Other Outcome Measures: Oestrogen, Oestrogen will be quantified in the plasma extracted from venous blood samples, to identify the menstrual cycle phases of the participants., Measured once before (pre) and once up to 1 week after (post) the intervention period|Progesterone, Progesterone will be quantified in the plasma extracted from venous blood samples, to identify the menstrual cycle phases of the participants., Measured once before (pre) and once up to 1 week after (post) the intervention period|Single nucleotide polymorphisms, Venous blood samples will be processed and analysed to identify single nucleotide polymorphisms, Measured once before (pre) and once up to 1 week after (post) the intervention period