An interventional study of Heat acclimation in Heat Stress, sponsored by University of Portsmouth. Completed at 1 site in United Kingdom. Open to male participants aged 18 Years to 45 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2023-12-06.
Sponsored by University of Portsmouth · Not applicable, Interventional, and Prevention
Repeated exposure to heat in a laboratory setting (acclimation) elicits a range of adaptations, which reduce heat illness risk and increase work capacity in the heat. Traditional approaches to heat acclimation require daily heat exposures of 1 to 2 hours over \~7 to 10 consecutive days. Heat acclimation approaches which reduce the number of days to achieve acclimation may have utility. The primary purpose of the proposed research is to determine whether it is possible to achieve a similar degree of heat acclimation to that seen with a traditional longer-term heat acclimation approach by increasing the frequency of heat exposure, utilising multiple daily heat exposures over a smaller number of days. Secondary aims of the research are to examine whether heat acclimation provides cross-adaptation to a hypoxic stressor and whether heat acclimation improves aerobic fitness.
Individuals are often required to operate in adverse conditions and may be exposed to prolonged periods of high ambient heat and humidity. High environmental temperatures impair work capacity and increase heat-illness risk. Repeated exposure to heat in a laboratory setting (acclimation) elicits a range of adaptations, which reduce heat illness risk and increase work capacity in the heat. However, traditional approaches to heat acclimation are time consuming, typically requiring daily heat exposures of 1 to 2 hours over \~7 to 10 consecutive days. This can be logistically difficult to implement and impractical, particularly in situations where an individual must be rapidly deployed. Therefore, heat acclimation approaches which reduce the number of days to achieve acclimation may have utility. In addition, recent research studies have suggested that adaptation to heat may improve tolerance to hypoxia (cross-adaptation) and improve aerobic fitness; these effects may also be beneficial in a military context. Therefore, the primary purpose of the proposed research is to determine whether it is possible to achieve a similar degree of heat acclimation to that seen with a traditional longer-term heat acclimation approach by increasing the frequency of heat exposure, utilising multiple daily heat exposures over a smaller number of days. Secondary aims of the research are to examine whether heat acclimation provides cross-adaptation to a hypoxic stressor and whether heat acclimation improves aerobic fitness. Heat acclimation will be evaluated using a range of whole-body (cardiovascular, thermoregulatory, psychophysiological) and biochemical markers.
111 studies on the registry are indexed under Heat Stress Disorders; 45 are open to participants now.
This study's enrollment of 37 is above the median of 24 across 97 interventional studies indexed under Heat Stress Disorders.
Browse Heat Stress Disorders studies →University of Portsmouth is the lead sponsor of 32 studies on the registry; 6 are open to participants now.
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Exclusion Criteria:
The traditional heat acclimation programme will consist of daily 75-minute heat exposures for eight consecutive days
Other: Heat acclimation
The condensed heat acclimation programme will consist of two consecutive days with four, 75-minute heat exposures undertaken on each day
Other: Heat acclimation
Repeated heat exposures with light exercise sufficient to elevate deep body temperature to \~ 38.5C
Reduction in the peak deep body temperature
Rectal temperature measurement during a heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Reduction in the resting deep body temperature
Rectal temperature measurement during a heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Reduction in the peak mean body temperature
Weighted rectal and mean skin temperature measurement during a heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Reduction in the resting mean body temperature
Weighted rectal and mean skin temperature measurement during a heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Increased plasma volume
Change in plasma volume calculated from resting haemoglobin and haematocrit prior to a heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Increased sweating rate
Sweating rate calculated from change in nude body mass and accounting for fluid consumption during a heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Reduced sweat sodium concentration
Sweating sodium concentration assessed from sweat collected in a custom sweat patch on the back during a heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Reduced exercise heart rate
Heart rate measured using chest telemetry during a heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Increased resting intracellular heat shock protein 70 content
Assessed in peripheral blood mononuclear cells obtained before a heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Increased post heat stress intracellular heat shock protein 70 content
Assessed in peripheral blood mononuclear cells obtained after a heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Increased resting intracellular heat shock protein 90 alpha content
Assessed in peripheral blood mononuclear cells obtained before a heat stress tests
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Increased post heat stress intracellular heat shock protein 90 alpha content
Assessed in peripheral blood mononuclear cells obtained after a heat stress tests
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Maximal oxygen uptake
Highest rate of oxygen uptake during graded cycling exercise
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Lactate threshold
Power output at 4 mmol.L-1 blood lactate during graded cycling exercise
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Gross mechanical efficiency
Percentage ratio of external work achieved compared to the total energy expenditure during graded cycling exercise below the lactate threshold
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Peak power output
Highest power output achieved during exhaustive cycling exercise
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Peripheral oxygen saturation during exposure to hypoxia
Assessed using ear or finger tip pulse oximetry during a hypoxic tolerance test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Heart rate during exposure to hypoxia
Assessed using chest telemetry during a hypoxic tolerance test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Minute ventilation during exposure to hypoxia
Expire volume of air per minute during a hypoxic tolerance test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Plasma neutrophil gelatinase-associated lipocalin
Concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Urine neutrophil gelatinase-associated lipocalin
Concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Plasma kidney injury molecule-1
Concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Urine kidney injury molecule-1
Concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Tissue inhibitor of metalloproteinase 2
Urine concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Insulin-like growth factor-binding protein 7
Urine concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Intestinal fatty acid binding protein
Serum concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Soluble cluster of differentiation 14
Plasma concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Lipopolysaccharide binding protein
Plasma concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Interleukin-6
Plasma concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Cortisol
Plasma concentration change pre to post heat stress test
Time frame: Pre heat acclimation intervention (up to 1 week) to post heat acclimation intervention (up to 1 week)
Plan to share: No — Data will be published as measures of central tendency and dispersion (e.g. Mean and Standard deviation)
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University of Portsmouth