Clinical trial NCT04160741: Effects of Solar Radiation on Human Function and Cognition
Official title: Effects of Solar Radiation on Human Function and Cognition
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Heat Stress
Heat Strain
Keywords: heat stress
heat strain
solar radiation
responses
cognition
thermal
Lead sponsor: University of Thessaly
Sponsor class: OTHER
First posted: 2019-11-13
Enrollment: 7
Sex: MALE
Minimum age (years): 18
Maximum age (years): 75
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: PREVENTION

Brief summary: Solar radiation is a physical phenomenon which interacts with any human being throughout its life on earth. This interaction is associated with numerous physiological functions, as well as a broad spectrum of deleterious effects on human health and wellbeing. The aim of this study is to elucidate the effects of solar radiation on human function and cognition in environmental conditions characterized by the same thermal stress.

Detailed description: Volunteers were exposed to four different environmental conditions \[two hot environments: 30°C WBGT (1st: air temperature = 32.6°C; relative humidity = 30%; wind speed = 0.5 m/s; solar radiation = 800 W/m2 and 2nd. air temperature = 40.6°C; relative humidity = 30%; wind speed = 0.5 m/s; solar radiation = 0 W/m2) and two neutral environments: 20°C WBGT (1st: air temperature = 19.1°C; relative humidity = 30%; wind speed = 0.5 m/s; solar radiation = 800 W/m2 and 2nd. air temperature = 28.5°C; relative humidity = 30%; wind speed = 0.5 m/s; solar radiation = 0 W/m2\], over an equal number of days. The aforementioned environmental scenarios were randomly allocated for each volunteer. To minimize participant bias, the true purpose of the study was hidden from the volunteers. Of course, once the data collection was completed, all volunteers were informed about the true purpose of the study and gave their permission to analyze and publish these data. During this blinded randomized controlled trial, all volunteers participated four times in an experimental protocol with a total duration of 03:20:00, following an hour of preparation and baseline tests. The protocol had three main time periods \[rest (two hours), work (cycling) at 100 W (one hour), and recovery (twenty minutes)\]. Anthropometrical data \[age; body stature (Seca 213; seca GmbH \& Co. KG; Hamburg, Germany); body mass (BC1000, Tanita corporation, Tokyo, Japan); body fat (DXA scan: Lunar DPX Madison, GE Healthcare, Wisconsin, USA); and lean mass (DXA scan: Lunar DPX Madison, GE Healthcare, Wisconsin, USA)\] were collected two days prior to the experiments.

Volunteers were euhydrated prior to the experiments. Hydration status was assessed using a handheld refractometer (ATAGO Ltd, Tokyo, Japan) and determined as either euhydrated (USG \< 1.020) or dehydrated (USG ≥ 1.020) according to the current guidelines. Water consumption was restricted during the experimental protocol. The same clothing consisting of a light-blue t-shirt (100% cotton), a black exercise short pant (100% polyester), and a pair of medium-high socks (100% cotton) were used by volunteers throughout the experiments. A pair of sunglasses was mandatory to be worn throughout the experiments. Furthermore, experiments took place during the same hour of the day for each participant and an 8-hour fasting was ensured prior to the experiments. Furthermore, participants were requested to avoid caffeine and alcohol consumption for at least twelve hours before the experiments, as well as to avoid salt and sugar consumption eight hours before the experiments.

During the study, continuous heart rate, core temperature, mean skin temperature, skin blood flow, and sweat rate were measured. Specifically, heart rate was collected using wireless heart rate monitors (Polar Team2. Polar Electro Oy, Kempele, Finland). Core temperature was collected using telemetric capsules (BodyCap, Caen, France). Skin temperature from four sites was measured using wireless thermistors (iButtons type DS1921H, Maxim/Dallas Semiconductor Corp., USA) and was expressed as mean skin temperature according to Ramanathan \[mean skin temperature = 0.3(chest + arm) + 0.2(thigh + leg). Skin blood flow was measured with a laser Doppler flowmeter (PeriFlux 4000, Perimed, Stockholm, Sweden) at right forearm (brachioradialis) and leg (gastrocnemius). The probe (PROBE 413 Integrating Probe, Perimed, Stockhold, Sweden) was held in place with a plastic holder (PH 13, Perimed, Stockhold, Sweden). Sweat rate was measured at three regions \[forehead, thigh (quadricep), and arm (bicep)\] using ventilated capsule method. Thermal comfort (1 = comfortable; 5 = extremely uncomfortable), thermal sensation (-3 = cold; +3 = hot), and perceived exertion (6 = no exertion at all; 20 = maximal exertion), alongside cognitive performance (vigilance, divided attention, memory test, and reaction time) were assessed at baseline, pre work condition (01:40:00), and post work (03:00:00) conditions. Volunteers entered the chamber five minutes prior to the experiments to install data loggers and accompanied sensors on their body.

Eligibility criteria: Inclusion Criteria:

* Healthy non-smoker individuals who exercise at least three times per week

Exclusion Criteria:

* Non healthy individuals and smokers

Primary outcomes:
measure: Heart rate
timeFrame: 03 hours and 20 minutes
measure: Mean skin temperature
timeFrame: 03 hours and 20 minutes
measure: Core body temperature
timeFrame: 03 hours and 20 minutes
measure: Skin blood flow
timeFrame: 03 hours and 20 minutes
measure: Sweat rate
timeFrame: 03 hours and 20 minutes
measure: Perceived exertion
timeFrame: Participants were assessed at baseline and every half an hour up until the end of the protocol at "hour 3".
measure: Cognitive performance (Vigilance)
timeFrame: Participants were assessed at baseline, at 1 hour and 40 minutes, and at "hour 3".
measure: Thermal comfort
timeFrame: Participants were assessed at baseline and every half an hour up until the end of the protocol at "hour 3".
measure: Thermal sensation
timeFrame: Participants were assessed at baseline and every half an hour up until the end of the protocol at "hour 3".
measure: Cognitive performance (Divided Attention)
timeFrame: Participants were assessed at baseline, at 1 hour and 40 minutes, and at "hour 3".
measure: Cognitive performance (Memory Test)
timeFrame: Participants were assessed at baseline, at 1 hour and 40 minutes, and at "hour 3".
measure: Cognitive performance (Reaction Time)
timeFrame: Participants were assessed at baseline, at 1 hour and 40 minutes, and at "hour 3".
Secondary outcomes:
Other outcomes:
Locations:
city: Tríkala
country: Greece
facility: FAME Lab, Department of Exercise Science, University of Thessaly
state: Thessaly
Study officials:
affiliation: andreasflouris@gmail.com
name: Andreas Flouris
role: PRINCIPAL_INVESTIGATOR
References: