Physiological and Thermoregulatory Responses of Body Cooling During Cycling in a Hot Environment
Condition: Hyperthermia
MeSH terms: Hyperthermia
Study type: Interventional

Summary: 
      BHSAI is developing a computational system that provides early alerts of a rise in core body
      temperature to help reduce the risk of heat injury in the field and during training. The goal
      of the body temperature alerting system is to use it during rest, exercise in the heat and
      during body cooling. Using this system during cooling will allow healthcare professionals and
      military personnel monitor core temperature to ensure cooling is effective (and prevent
      hypothermia). Therefore, the primary purpose of this investigation is to validate a body
      temperature alerting system using physiological responses that occur during rest, exercise in
      the heat and during body cooling. Multiple cooling modalities will be validated. This study
      is expanding on a previous intervention IRB#H20-0010 (BHSAI Cooling Study), but will examine
      body cooling during more intense exercise and while cycling. We will also examine the
      effectiveness of each cooling modality (passive cooling, mist-fan cooling, hand/forearm
      immersion, ice towel) on physiological variables after exercise in the heat.
    

Detailed description: 
      Design

      The study will be completed in the following timeline:

      Visit 1: Baseline and VO2max Testing

      Vist 2: Metabolic Heat Production Visit

      Visit 3-6: Trial 1, 2 ,3, 4

      Visit specific information is described below, however, specific data collection protocols
      for dependent variables and procedures are included below the description of the study
      design. Participants will be asked to sign a photo/video release form (Appendix H) to be used
      in research projects, scientific publications/conferences and for educational purposes.
      Participants may be videoed or photographed while exercising or resting in the environmental
      chamber. Participants will be assigned after medical clearance is granted.

      Visit 1: Baseline and VO2max Testing

      Participants who are approved to participate will be scheduled for a baseline and VO2max
      testing day. Basal metabolic rate (BMR) will be measured upon arrival during the baseline
      visit. The participant will lay supine with a ventilated hood covering their head and torso.
      The ventilated hood will be attached to a hose connected to a metabolic cart. The metabolic
      cart will continuously measure respiratory exchange ratio, oxygen consumption, and substrate
      utilization. The participant will remain under the hood for approximately 30 minutes. Upon
      completion of BMR, participants will provide a urine sample in a clean urine cup. Urine
      specific gravity and urine color will be assessed. Nude body mass will also be recorded.
      Privacy will be afforded for each participant while obtaining body mass measures by taking
      measurements with the participant alone in a private room behind a solid, closed door, and
      the research reading the scale outside of the room. Participants will only be permitted to
      continue to the VO2max test if the euhydrated criteria of a urine specific gravity (USG)
      ≤1.025 is met. If the participant arrives with a USG between 1.020 and 1.025, the subject
      will be asked to drink 500 mL of water to ensure proper hydration status. If USG is greater
      than 1.025 the subject will be rescheduled for a different day. Height will be measured with
      a tape measure on Visit 1. Percent body fat will be measured using Air displacement
      plethysmography (BodPod®; Cosmed, Software Version 4.2+, Concord, CA, USA). This will take
      less than ~5 minutes to complete. This information will be used to describe the subject
      demographics. Participants will also be asked to complete a maximal oxygen uptake (VO2max)
      test on a treadmill and on a cycle ergometer in a thermoneutral environment with about 30
      minutes to one hour between. This test will provide aerobic fitness levels of the
      participants which will be compared between the two exercise protocols. Participants will
      also be asked about their average weekly physical activity (Appendix K). This visit will take
      approximately 1-2 hours.

      Visit 2: Metabolic Heat Production Visit

      In order to prescribe appropriate exercise intensity, heat production must be controlled.
      Heat production will be prescribed utilizing a graded exercise test (3-5 minute stages) in
      the heat (same environmental temperature as trials) that will measure metabolic data via
      collection of expired air utilizing 2-way non-rebreathing mask in order to calculate heat
      production and appropriately choose cycling intensities to compare between groups of research
      participants. This test will occur following the baseline visit. The study procedures will
      mimic those of trials (described below), with the exception of the exercise protocol. The
      exercise protocol will take approximately 20 minutes to complete. It will include 5 stages of
      exercise (graded stages). The participant will wear the ACU during this visit.

      Visit 3-6: Trials 1-4

      Participant numbers will be randomly assigned, and 4 trials (mist-fan, forearm, passive
      cooling, ice towel) will be ordered with a random number generator and assigned to a
      participant number.

      These orders will be counterbalanced between participants to ensure that there is not an
      order effect. Each participant will complete four trials as part of the study. Participants
      will be allowed to make-up trial visits if they are sick, suffer an injury or do not meet
      hydration requirements. Participants will be asked if they have a current illness or taking
      medications to determine whether they can complete the exercise trial. The participant's
      visit will be rescheduled if they have a fever, current illness or taking medications that
      influence body temperature. Participants will complete four trials on four separate days.

      Trial #

      Cooling Intervention

      1

      Passive Cooling

      2

      Mist-fan Cooling

      3

      Forearm Immersion

      4

      Ice Towel

      The exercise protocol and recovery portions of this study will be conducted in a climatic
      chamber with ambient temperature approximately 30-40°C and relative humidity at approximately
      30-70%. Participants will drink ad libitum throughout the exercise trial.

      Upon arrival to the lab, participants will be asked to indicate if they have consumed alcohol
      or caffeine in the last 24 hours and 12 hours, respectively. They will not be asked to
      specify exactly what they have consumed, but if they provide a positive indication, their
      trial will be rescheduled for another day. Participants will provide a small urine sample in
      a clean urine cup, and a nude body mass will be measured. Upon arrival to the lab, hydration
      status will be assessed by urine specific gravity, nude body mass and urine color.
      Participants will only be permitted to continue to the exercise trial if the euhydrated
      criteria of a urine specific gravity (USG) ≤1.025 is met. If the participant arrives with a
      USG between 1.020 and 1.025, the subject will be asked to drink 500 mL of water to ensure
      proper hydration status. If USG is greater than 1.025 then the subject will be rescheduled
      for a different day. Participants will be given instructions at the prior visit about how to
      obtain desired hydration status for the upcoming trial. Researchers will insert an esophageal
      probe. Only trained personnel are permitted to insert the esophageal probe (no undergraduates
      will be allowed). Participants will insert a rectal probe and wear a heart rate monitor
      strap. Additionally, participants will wear 9-site Biopac skin temperature sensors.
      Researchers will apply the skin temperature sensors with medical tape to the participants'
      chest, upper arm, forearm, thigh, neck, abdomen, thigh, back, and calf (anterior and
      posterior). Participants will also wear iButtons (wireless skin temperature sensors) on their
      chest, upper arm, forearm, thigh, and calf (anterior and posterior). The participants will
      also be asked to complete a subjective sleep questionnaire upon arriving to the lab.
      Participants will wear an active combat uniform (ACU) during the exercise trials. Three ADU
      sizes for the blouse and pants (small, medium, large) will be available for the participants.
      A belt will be used to ensure the ACU fits appropriately. Participants will not be able to
      keep the ACU- ADUs will be washed (according to manufacturer's instructions) and re-used for
      participants. ADU manufacturer's instructions is identical to standard washing cycle
      (detergent and washing machine dry). The ACU will be weighed before and after use to measure
      sweat captured in the clothing. Participants will wear the wrist-based devices (provided by
      BHSAI) on their non-dominant arm throughout the testing. The wrist device must be placed
      approximately 1-inch proximal to the wrist and be fitted snugly for accurate heart-rate
      measurements. The wrist device is used to estimate heart rate using infrared technology. The
      wrist device estimates of heart rate will be compared to the polar heart rate monitor (gold
      standard). The body alerting system uses heart rate from the wrist device and the
      environmental conditions to estimate body temperature. The sponsor of the study will use
      rectal temperature and the 7-site skin temperature sensors to alter the algorithm (not in
      real time- from the collected data) to better estimate body temperature. The future goal is
      to have the body alerting system imbedded in the watch. Participants will wear another
      wrist-based device (WHOOP) on the arm that does not have the BHSAI device. The WHOOP device
      will monitor heart rate variability and sleep. Participants will be asked to wear this device
      daily for the duration of the study.

      Participants will enter the environmental chamber and sit for 30 minutes to become
      equilibrated. The environmental chamber will be set to 30-40°C ambient temperature, 30-70%
      relative humidity After baseline measures of heart rate, rectal temperature, participants
      will complete the perceptual indices. Participants will also complete an environmental
      symptoms questionnaire (ESQ).

      The trial will consist of two 40-minute intervals of cycling from 7W/kg to 15 W/kg. Each
      40-minute exercise block will be followed by a rest break where cooling will occur.
      Participants will be allowed to drink ad libitum throughout the exercise trial. The
      participant will be cooled for approximately 30 minutes with their assigned cooling modality.
      Rectal and esophageal temperature, skin temperature, heart rate, perceptual measures, and
      mood (POMS, described below) will be collected at various time points before, during, and
      after exercise and cooling. Metabolic heat production will be measured using indirect
      calorimetry (mask connected to metabolic cart) during all four trials.

      Passive Cooling: Participants will be asked to sit in a chair in the climate chamber for
      passive cooling.

      Mist-fan cooling: A mist-fan will be placed next to the participant and will mist-fan only
      their hands and forearms during mist-fan cooling. Participants will be asked to roll up their
      ADU sleeves to increase skin surface area. The temperature of the mist and wind speed of the
      fan will be recorded.

      Forearm immersion: The participant will place their forearm in approximately 20°C water
      during forearm immersion.

      Ice Towel: a towel that can hold water for extended periods will be used and submerged in an
      ice-water mixture (~2 C). Researchers will gently squeeze the towel to remove excess water
      (but remain saturated with water) and then apply to both forearms and hands snuggly so that
      there is no air gap between the towel and the extremity. Apply for 1-5 minutes and then
      replace it with another fresh, cold towel. This step would ensure that the forearms and hands
      have near about constant application temperature as the towel would get warm over the
      application period. The process will be repeated for the entire cooling duration.

      Data collection will be divided into two separate phases. A pilot study will be first
      conducted in which the first two participants will complete all study laboratory visits. Data
      from those trials will be shared with the sponsor for review before continuation of data
      collection. Participants will undergo the same procedures for the pilot testing as regular
      testing. Pilot testing data will be included in the dataset. Following approval from the
      sponsor, data collection will resume. Each trial will be approximately 4 hours.

      All devices will be properly cleaned according to manufacturer's instruction prior to use by
      other participants.
    

Intervention name(s): Forearm coolng; Wet-towel cooling; mist-fan; passive cooling
Intervention type(s): Other; Other; Other; Other
Intervention description(s): forearm immersion will be performed for active cooling assessment; Wet towels will be wrapped around the participant's arms for active cooling; a mist-fan will be placed in front of the participant for active cooling; participants will sit in a chair and "passively cool" (no active intervention)
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Participants received four cooling treatments on separate study visits: 1) passive cooling 2) forearm cooling 3) mist-fan cooling, 4) ice towel coolng
Masking: None (Open Label)
Primary purpose: Treatment