Design This laboratory study is a randomized, counterbalanced, crossover design involving 20 participants (20 males) from the local community and university. This project will be conducted within the thermal physiology laboratory, complete with a climatic chamber (Cantrol, CES +13/+44) located within the Human Performance Laboratory (HPL) at the University of Connecticut. The investigators expect each interested individual will complete both phases included within the study design within a randomized, counterbalanced order.
Participant grouping orders will be randomly assigned by the project's lead student investigator (Jeb Struder). Each phase will be fairly similar in procedures completed; however, one phase will be completed with a trial that introduces a biomedical intervention (sodium bicarbonate topical lotion; PR group), while the other phase will be completed with a trial that introduces a placebo (PLA group) product similar to the biomedical intervention. Approximately 24 hours should pass between the completion of each session within a phase of the study. Additionally, approximately 3 days should pass between the completion of a phase and the initiation of the next phase (5th session completed).
Environmental Conditions Sessions I, II, and III of both counterbalanced groups (PR and PLA) will all be completed within thermoneutral conditions. Session IV of both counterbalanced groups (PR and PLA) will be conducted within the climatic chamber set to a climate with ambient temperature at approximately 33C (91.4F) and relative humidity at approximately 25%.
Baseline Assessments (PR/PLAI, PR/PLAII, PR/PLA III) Baseline visits should be completed over 3 consecutive days for the establishment of baseline measurements regarding the participant's body weight, dietary behaviors, and hydration status. Each assessment will be performed at the relatively same time of day (early to late morning) and will involve approximately 30 minutes spent within the laboratory space of the Human Performance Laboratory (HPL). All Baseline Assessment sessions will consist of fairly similar data collection procedures and will begin with the participant providing the completed 24-h dietary recall log, thirst perception scale, and filled urine jug to the administrating researcher. Additionally, the participant will be asked to provide a morning urine sample and nude body weight for the assessment of session-specific hydration status and Fluid Retention Index (FRI). Furthermore, once these tasks are completed, an HPL trained researcher will conduct a blood draw for the collection of approximately ½ teaspoon of blood. Each session will deviate slightly in additional tasks required for completion.
Day 1 (PR/PLAI): After the collection of a morning urine sample and nude body weight measurement, the participant's height (for additional anthropometrics) and resting blood pressure (for safety precautions) will be measured. Additionally, after the completion of the blood draw, the final task for this session will be the participant's familiarization to the Cognitive/Perceptual Battery tasks that you will be tested during Session 4 (PR/PLAIV).
Day 2 (PR/PLAII): After the collection of a morning urine sample and nude body weight measurement, the participant will be asked to rest within a comfortable position for approximately 10-15 minutes for the measurement of their resting heart rate.
Day 3 (PR/PLAIII): After the collection of a morning urine sample and nude body weight measurement, the participant will have their body fat percentage measured via handheld Lange Skinfold Calipers.
Intervention Trial (PR/PLAIV) Pre-Testing Procedures Prior to completing all Intervention Trial visits, participants will be asked to drink 500 mL of water before going to bed and an additional 500 mL of water upon waking to ensure proper hydration. If morning sample urine USG is ≤1.020, participants will be cleared to participate. If the participant arrives with a urine USG between 1.020 and 1.025, the subject will be asked to drink an additional 500 mL of water prior to entering the chamber to ensure proper hydration status. If participants arrive at the lab with a urine USG \>1.025, the visit will be rescheduled for the following day. In addition to completing a morning urine spot sample, participants will be asked to complete a nude body mass measurement as well as provide their completed thirst perception scale, dietary recall log, and urine jug. Furthermore, using the urine and nude body weight measurements collected, the session-specific FRI will be assessed. Afterwards, the participant will be provided a standardized breakfast. Once the participant has indicated they are finished with their meal, resting blood pressure measurements will be conducted. Once all measurements have been completed, participants will have a venous cannula inserted by an HPL trained research team member. Finally, prior to entering the environmental chamber, participants will be instructed to privately insert the rectal thermometer 10-15 cm beyond the anal sphincter in addition to completing an additional nude body mass measurement and being fitted with a heart rate strap by the administrating research team.
Data Collection - Initial 120-minutes Upon the completion of participant arrival procedures, participants will then be permitted to enter the environmental chamber (\~33C \[91.4F\], \~25% relative humidity) where they will be instructed to sit down and begin a 30-minute period of environmental equilibration. Once this period has been initiated the participant will be asked to complete their baseline measurements in regard to the Cognitive/Perceptual Battery. After the equilibration period has been completed, the participant will have their resting blood pressure measured, provide a baseline blood sample (\~11 mL), and then provide both a urine sample and nude body weight measurement. Once all of these tasks have been completed, the participant will be provided approximately 50 g of the topical lotion (i.e. PR Lotion or Placebo) to apply to their upper body. Afterwards, blood samples (\~3 mL) will be collected approximately 15- and 30-minutes post-lotion application. Furthermore, the hyperhydration protocol will be initiated at the 30-minute post-lotion application time point. During this time period, the first of 4 fluid boluses will be provided to the participant for consumption with instructions to consume all fluids provided within the allotted 15-minute time period before the provision of their next fluid bolus. Additionally, before the 3rd fluid bolus has been provided for consumption (identified as time point -30 min in Figure 4), another blood sample (\~11 mL) will be completed before completing the rest of the hyperhydration protocol.
Hyperhydration Protocol To induce hyperhydration, participants will drink a total fluid volume of approximately 25 mL/kg of fat free mass (FFM) of water. These solutions will be pre-measured and provided within four enclosed water bottles for consumption at a rate of approximately 6.5 mL/kg FFM about every 15 minutes within a duration of approximately 60 minutes.
Topical Solution Procedures Approximately 50 grams of the topical solution will be pre-measured into 2 separate plastic bags and provided to the participant for application. Participants will be instructed to apply the solution primarily to areas of their upper extremities which will include an identified area from the wrist up to the clavicular area of the shoulder in addition to their chest, neck, upper back, midsection, and lower back if enough solution is available. Application will be considered complete when the solution has been transmitted to the skin in a fashion to where no residue from the lotion is visible by researchers from the skin of the participant.
Data Collection - 3-hour Protocol Collection of Blood Samples Aside from the baseline blood sample collected around the -90-minute time point, an initial blood sample will occur at time point 0 min, where approximately 11 mL of blood will be collected via the inserted cannula. Similar blood samples will be collected at time intervals of approximately 60-minutes up to the completion of the data collection protocol, occurring around the 180-minute mark (approximately 3-hours). In total, approximately 72 mL of blood will be collected during the Intervention Trial, which is less than ¼ of the amount of blood collected during a blood donation.
Collection of Urine Samples and Body Weight Measurements For the collection of all urine spot samples, researchers will provide a clean cup and top to seal the capsule. Participants will be asked to provide a sample regardless of urgency to urinate at specific time points during the trial. If the participant is unable to provide a sample at the time point requested, no protocol deviation will be considered as the lack in sample provided will still be used towards the completion of data analysis. Furthermore, if the participant must provide a urine sample without being requested by a research team member, any urine expelled will be added to the amount collected (if any) during the next urine sample collection time point. Additionally, participants will be instructed to complete a measurement of nude body weight completed before the provision of a urine sample. Both the collection of urine samples and measurement of body weight will be completed within the privacy of a bathroom. Aside from the baseline measurement completed around the -90-minute time point, the initial urine sample collection and body weight measurement for the intervention (i.e. PR Lotion or Placebo) will approximately occur at time point 0-minutes and supplementary urine collection and body weight measurement will be completed in 30-minute intervals up to the end of the data collection period, occurring around the 180-minute mark (approximately 3-hours).
Completion of Cognitive/Perceptual Battery Aside from the baseline Cognitive/Perceptual Battery completed around the -115-minute time point, the initial Cognitive/Perceptual Battery will be completed at time point 0-minutes. Completion of supplemental Cognitive/Perceptual Batteries will be continually measured within a 60-minute time interval from time point 0-minutes until the completion of data collection which will coincide with the 180-minute time point (approximately 3-hours).
