Time Onset Sweat Sodium (TOSS) Study

NCT07464743 | Not Yet Recruiting

• 1 other identifier: 2509625720
• Study Type: interventional
• Target: 40
• Locations: 0 countries
• Sites: N/A

Brief Summary

Prior to each trial, you will be provided with urine jugs and food/fluid logs to record food and drink intake for 24hr. You will be asked to log food/fluid intake 24hr leading into trials. We ask that you match your diet for both trials, as much as possible. Also, we ask that you match caffeine consumption prior to trials. Lastly, we ask that you refrain from strenuous exercise and alcohol consumption for at least 12hrs leading into trials. Either of these exclude your participation in the study for safety reasons. You will be asked to provide a small urine sample upon arrival to the lab before trials. The purpose of this is to verify hydration prior to exercise in the heat. If you are not hydrated upon arrival, you will be provided and asked to drink 16oz (a bottle) of water prior to the trial. Just prior to, and following each long trial, you will be asked to provide a small saliva sample. To do this, you will be asked to actively produce saliva and guide it into a small container. This process takes \<5min. Next, you will have your nude body mass measured and you will be instrumented with a labbased sweat collection patch (large band-aid on the forearm), and the Hdrop sweat detection device on your left upper arm. The Hdrop will be synced with electronic applications (phone apps) to assure data collection. You will then self-insert a rectal thermistor \~15 cm past the anal sphincter to monitor core temperature throughout exercise (for safety purposes). You will also be fitted with a heart rate strap that goes around your chest. You will then be asked to enter the environmental chamber and exercise for 30min. This will serve as the short exercise trial aiming to assure comfort with the 120min exercise trials. Data will be collected during the short trial and comparisons will be made for the longer, 120min trials. The environmental chamber will maintain a consistent temperature (80-100 degrees F) and humidity (40 to 60 % relative humidity). You will be monitored for safety throughout exercise in all 3 trials, and you will be allowed to cycle (stationary bike) or run or walk (treadmill) at your own pace/intensity. Pace and intensity will be recorded during the first trial and attempts will be made to match exercise intensity for subsequent trials. Fluid consumption will be allowed during trials and will be matched between trials. In both trials, you will be allowed to drink for a 5min period at each 30min interval (30-35min, 60-65min and 90-95min). We will provide a sport drink of your flavor choice during exercise.

Conditions

Sweat Rate; Heat Effect; Sweat Sodium Concentration

Keywords

Sweat rate; Exercise in the heat; Sweat sodium; Validity

Outcome Measures

Primary Outcomes (2)

• Sweat rate (L/hr)

  Sweat rate is measured as body mass changes during exercise in the heat.

  0-30min; 30-60min; 60-90min; 90-120min - Every 30min during exercise in the heat

• Sweat [Na]

  Sweat \[Na\] will be assessed via sweat patches applied during exercise in the heat.

  Every 30min during trails with exercise in the heat.

Study Arms (2)

Short trial (30min exercise in the heat)

OTHER

Short trial. We will assess sweat rate and sweat-sodium losses during exercise in the heat.

Other: Exercise in the heat

Long trials (120min exercise in the heat)

OTHER

Long trial. we will assess sweat rate and sweat-sodium losses during exercise in the heat. We will also determine if 30min exercise trials accurately predict fluid and Na losses during 120min exercise in the heat.

Other: Exercise in the heat

Interventions

Exercise in the heat OTHER

Our trials will be conducted in an environmental chamber set to 80-100 degrees F and 40-60 relative humidity.

Long trials (120min exercise in the heat); Short trial (30min exercise in the heat)

Eligibility Criteria

• Age: 18 Years - 49 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Regular exercisers
• Otherwise healthy individuals
• Capable of running/jogging or cycling for 120min straight

You may not qualify if:

• Heat illness in the past 3 years
• Taking medications that alter fluid balance or Na retention
• Chronic conditions that contraindicate long duration exercise in the heat

Sponsors & Collaborators

• University of Arkansas, Fayetteville: lead

Related Publications (1)

• Bandiera D, de Bardonneche J, Margout-Jantac D, Dubois L, El Allaoui N, Rubio JSE, Aubin JC, Racinais S, Tessitore A, Pitsiladis Y. Sweat sodium composition and sweat loss estimation through wearable sensors and predictive equations in dry and humid hot conditions. Front Physiol. 2026 Jan 5;16:1717275. doi: 10.3389/fphys.2025.1717275. eCollection 2025.

  PMID: 41561158 BACKGROUND

MeSH Terms

Interventions

Exercise

Intervention Hierarchy (Ancestors)

Motor Activity; Movement; Musculoskeletal Physiological Phenomena; Musculoskeletal and Neural Physiological Phenomena

Central Study Contacts

Brendon P. McDermott, PhD

CONTACT

14795754670; brendonm@uark.edu

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: OTHER
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Model Details: Participants will complete 3 trials each. One trial is 30min in duration, while the last 2 are 120min, involving exercise in the heat. The longer trials will be matched.

Study Record Dates

• First Submitted: March 2, 2026
• First Posted: March 11, 2026
• Study Start: February 16, 2026
• Primary Completion: May 1, 2026
• Study Completion: August 1, 2026
• Last Updated: March 11, 2026

Record last verified: 2026-03

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ICF, CSR