Dehydration, Hot Weather; Adverse Effect, Hyperthermia, Kidney Dysfunction, Kidney Injury
Conditions
Brief summary
An epidemic of chronic kidney disease is occurring in laborers who undertake physical work outdoors in hot conditions. The reason for this is unknown, but may be related to kidney dysfunction caused by increases in body temperature and dehydration. The current heat stress recommendations for workers were not developed with regards for kidney health. The purpose of this study is to determine if the current recommendations protect against kidney dysfunction.
Interventions
OTHER23.0°C WBGT - Fixed Work Rate
For four hours, participants will walk on a treadmill to elicit 430 W of metabolic heat production in the following conditions: 23.0°C WBGT (29°C, 46% relative humidity) @ 60 min exercise per hour
OTHER25.5°C WBGT - Fixed Work Rate
For four hours, participants will walk on a treadmill to elicit 430 W of metabolic heat production in the following conditions: 25.5°C WBGT (31°C, 52% relative humidity) @ 45 min exercise per hour
OTHER27.5°C WBGT - Fixed Work Rate
For four hours, participants will walk on a treadmill to elicit 430 W of metabolic heat production in the following conditions: 27.5°C WBGT (33°C, 53% relative humidity) @ 30 min exercise per hour
OTHER28.5°C WBGT - Fixed Work Rate
For four hours, participants will walk on a treadmill to elicit 430 W of metabolic heat production in the following conditions: 28.5°C WBGT (34°C, 54% relative humidity) @ 15 min exercise per hour
OTHER35.5°C WBGT - Fixed Work Rate
For four hours, participants will walk on a treadmill to elicit 430 W of metabolic heat production in the following conditions: 35.5°C WBGT (40°C, 65% relative humidity) @ 15 min exercise per hour
OTHER26.0°C WBGT - Fixed work-to-rest ratio
For four hours, participants will walk on a treadmill at differing levels of metabolic heat production and environmental conditions (noted below), but at a fixed work-rest ratio of 30 minutes per hour. 26.0°C WBGT (31°C, 55% relative humidity) @ 530 W metabolic heat production
OTHER30.5°C WBGT - Fixed work-to-rest ratio
For four hours, participants will walk on a treadmill at differing levels of metabolic heat production and environmental conditions (noted below), but at a fixed work-rest ratio of 30 minutes per hour. 30.5°C WBGT (36°C, 55% relative humidity) @ 230 W metabolic heat production
OTHER30.5°C WBGT - Fixed work-to-rest ratio (high intensity)
For four hours, participants will walk on a treadmill at differing levels of metabolic heat production and environmental conditions (noted below), but at a fixed work-rest ratio of 30 minutes per hour. 30.5°C WBGT (36°C, 55% relative humidity) @ 530 W metabolic heat production
Sponsors
State University of New York at Buffalo
Indiana University
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Outcomes Assessor)
Masking description
The participant will not be directly informed of the experimental conditions and will be blinded to the hypotheses. The outcomes assessor will be blinded to the experimental conditions when analyzing the data.
Intervention model description
This study will systematically examine the NIOSH recommendations for prescribing work-to-rest ratios during occupational heat stress on kidney function.
Eligibility
Sex/Gender
ALL
Age
18 Years to 44 Years
Healthy volunteers
Yes
Inclusion criteria
* Men and women * 18-44 y old * Body mass index ≤35.0 kg/m2 * Self-reported to be healthy.
Exclusion criteria
* Not within defined age range * Estimated glomerular filtration rate (eGFR) \< 60 mL/min/1.73m2 * Deemed highly active according to the physical activity questionnaire (i.e., \>3500 MET\*min/wk) * Body mass index \>35.0 kg/m2 * Current or history of any renal disease, heart disease, stroke, immune or autoimmune disease, and/or gastrointestinal disease/surgery * Hypertension during screening (systolic blood pressure \>139 or diastolic blood pressure \>89) * Using medications that blunt the physiological response to exercise (e.g., beta blockers) * Prescription medication with a known side effect of impaired temperature regulation or fluid balance (e.g., diuretics) * Positive pregnancy test at any time during the study or breast feeding * Current tobacco or electronic cigarette use or consistent use within the last 2 years * Inability to safely complete the peak oxygen uptake test
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Peak urinary [IGFBP7•TIMP-2] | through study completion, up to 20 weeks | Kidney injury marker |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Urinary IGFBP7 | through study completion, up to 20 weeks | Kidney injury marker |
| Urinary TIMP-2 | through study completion, up to 20 weeks | Kidney injury marker |
| Urinary IL-18 | through study completion, up to 20 weeks | Kidney injury marker |
| Urinary NGAL | through study completion, up to 20 weeks | Kidney injury marker |
| Renal artery blood velocity | through study completion, up to 20 weeks | Index of kidney blood flow |
| Segmental artery blood velocity | through study completion, up to 20 weeks | Index of kidney blood flow |
| Urinary L-FABP | through study completion, up to 20 weeks | Kidney injury marker |
Other
| Measure | Time frame | Description |
|---|---|---|
| Urine osmolality | through study completion, up to 20 weeks | Hydration status variable |
| Blood and plasma volume | through study completion, up to 20 weeks | Hydration status variable |
| Urine specific gravity | through study completion, up to 20 weeks | Hydration status variable |
| Plasma copeptin | through study completion, up to 20 weeks | Hydration status variable |
| Whole-body sweat rate | through study completion, up to 20 weeks | Hydration and heat strain variable |
| Fractional excretion of electrolytes | through study completion, up to 20 weeks | Kidney function variable |
| Free water clearance | through study completion, up to 20 weeks | Kidney function variable |
| Serum uric acid | through study completion, up to 20 weeks | Kidney function variable |
| Urinary uric acid | through study completion, up to 20 weeks | Kidney function variable |
| Creatinine clearance | through study completion, up to 20 weeks | Kidney function variable |
| Core body temperature | through study completion, up to 20 weeks | Heat strain variable |
| Mean skin temperature | through study completion, up to 20 weeks | Heat strain variable |
| Oxygen uptake | through study completion, up to 20 weeks | Heat strain variable |
| Heart rate | through study completion, up to 20 weeks | Heat strain variable |
| Blood pressure | through study completion, up to 20 weeks | Heat strain variable |
| Percentage change in body weight | through study completion, up to 20 weeks | Hydration status variable |
| Plasma osmolality | through study completion, up to 20 weeks | Hydration status variable |
Countries
United States
Outcome results
None listed