Occupational InjuriesNCT06442956
Effect of Rapid Heat Stress on Firefighters Musculoskeletal Injury Risk
A study testing Rapid Heat Condition and Gradual Heat Condition in people with Occupational Injuries and Heat Stress, run by Louisiana State University Health Sciences Center Shreveport at 1 site in United States.
Trial summary
This study will examine the effect of heat stress on factors that influence musculoskeletal injury risk in firefighters. Participants will attend 4 data collection sessions. 1: informed consent, screening, and familiarization. 2: pre-tests (strength, balance, and movement quality). Read more about this study
- Who is it for?
- Ages 18 to 57 yearsHealthy volunteers can take part
- Conditions the study is for
- Occupational Injuries, Heat Stress, Leg Injury
- What is being tested?
- Rapid Heat Condition and Gradual Heat Condition
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 26 participants
- Where
- 1 siteUnited States
- Study dates
- 7 Jan 2025to 7 Nov 2025
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 57 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- professional firefighter
- healthy per the Physical Activity Readiness Questionnaire+ screening
Who cannot join
- unable to swallow core temperature capsule
- unable to follow pre-testing hydration criteria
- musculoskeletal injury in the past 3 months that limits ability to perform outcome measures
- females with known pregnancy (risk of hyperthermia to fetus)
Trial locations and contacts
1 site in 1 country.
About this study
Official title: The Impact of Rapid Heat Stress on Firefighters' Strength, Dynamic Balance, and Movement Quality
This study will examine the effect of heat stress on factors that influence musculoskeletal injury risk in firefighters. Participants will attend 4 data collection sessions. 1: informed consent, screening, and familiarization. 2: pre-tests (strength, balance, and movement quality). 3: heat stress (rapid or gradual) followed by post-tests (strength, balance, and movement quality). 4: heat stress (rapid or gradual) followed by post-tests.
Read the detailed description
This study utilizes a crossover design, with participants acting as their own controls and participating in both the control (gradual uncompensable heat) and experimental (rapid heat stress (RHS)) conditions. The independent variable is the type of heat stress (uncompensable or rapid). The dependent variables are: peak concentric muscle torque (hip abductors, hip adductors, knee flexors, knee extensors), dynamic balance (Y-Balance Test, Firefighter-Specific Functional-Balance Test (FFSFBT)), and frontal plane movement quality (Forward-Step-Down Test (FSDT)). These will be measured three times, once during pre-testing and twice during post-testing as described below.
The study will consist of four visits. Visit one will be the informed consent and familiarization to the outcome measures. Participants will be educated on filling out the 24-hour food/drink diary, and asked to standardize their diet as close as possible to this record the 24 hours before visits 2, 3, and 4. Injury history and demographic data will be collected at visit 1.
Visit two will be the pre-test data collection, which will occur at approximately 22°C. Participants will complete all outcome measures (torque, balance, movement quality measures). Body composition will also be measured in the BodPod at this time.
Before visits 2, 3, and 4, participants will follow the safety guidelines outlined below to ensure proper hydration:
- 48 hours before: no heat stress (will contact participant to determine if they have been called out to a live fire. Data collection will be postponed if so)
- 24 hours before: no alcohol consumption, no energy drink consumption (normal coffee/tea is allowed)
- 24 hours before: no physical activity (exercise or vigorous play)
- 24 hours before: drink 3.7L of total water to make sure to be well-hydrated
- 2 hours before: eat last meal
Visits three and four will consist of a steady-state treadmill protocol inside the environmental chamber (37-38°C, 50% humidity) followed by post-test measures. During either session three or four, the participant will don his/her firefighting gear (jacket, pants, hood, boots, gloves) and perform the treadmill test with the gear on. This is the RHS trial and will be denoted GEAR. In the other session, the participant will wear exercise clothes (shirt and shorts) plus a weighted backpack to replicate the weight of the gear. This is the gradual uncompensable heat stress trial and will be denoted NOGEAR. The order of the GEAR and NOGEAR sessions will be randomized and counterbalanced to prevent crossover effects.
Upon arrival for the pre-testing visit (session two), participants will be measured for height using a stadiometer and weight. Body composition will be measured once with the BodPod (Cosmed, USA). They will warm up for five minutes on an exercise bike or treadmill then proceed with taking the outcome measures.
Upon arrival for visits three and four, participants will be weighed again. A urine sample will be collected to assess hydration status. They will swallow the core temperature (Tc) capsule 40-45 minutes prior to the start of the session using a small amount of 20°C water, with no further water ingestion throughout the protocol to avoid artificially lowering Tc. Participants will be fit with the Equivital EQLife Monitor (Equivital, NY) system to record heartrate (HR) and Tc. They will then perform the treadmill protocol, and post-test measures will be completed immediately following the cessation of the treadmill test with removal of their gear. They will be weighed following exercise to determine changes in body weight due to sweating.
Sessions three and four will be separated by at least seven days to reduce the influence of heat acclimatization and fatigue. Continuous monitoring of Tc and HR will help ensure participant safety.
The treadmill exercise protocol begins with a graded approach to reach aerobic steady state. The treadmill protocol includes an initial five-minute stage at 3 miles per hour and a 0% grade, followed by increases in percent grade of 4% at minute 5 and 8% at minute 10 and continued throughout the test. Following the final planned incremental increase in treadmill incline, the incline will then be adjusted to ensure that the subject remains at steady-state for the duration of the protocol, defined by a respiratory exchange ratio between 0.9-0.99 using the lab's metabolic cart (Parvomedics, USA). HR, rating of perceived exertion (RPE), thermal comfort, and thermal sensation will be recorded at each 0.5°C interval. The treadmill test will be stopped when participants either reach a Tc of 39°C or a volitional maximum (participant is unable to continue exercise). The investigators will also halt the test if signs of excessive heat stress are present (unsteady gait, confusion, dizziness, slurred speech, etc.) Should the participant not meet either termination criteria, there will be a 50 minute time limit for the treadmill protocol for the GEAR condition and 2 hour limit for the NOGEAR condition. Both GEAR and NOGEAR sessions will begin with the same treadmill test.
Following the treadmill test, the participants will complete the post-test outcome measures. These consist of isokinetic torque of the hip abductors and adductors, isokinetic torque of the knee flexors and extensors, the Y-Balance Test, the FFSFBT, and FSDT. Participants will doff their gear immediately following cession of the treadmill test. For unilateral tests, the dominant leg will be recorded and used for these tests; this is the leg used to kick a ball. Outcome measure order will be standardized for each participant with testing order based on primary outcomes and difficulty of each test. The FSDT will be performed first, as this is the primary outcome and previous research showed that recovery after a maximal exertion stimulus happens quickly. The FFSFBT will be performed next, followed by the Y-Balance Test. Isokinetic testing will be last due to the fatiguing nature of this testing. Hip muscles will be tested first, followed by thigh muscles. Three minutes will be allotted for rest and instruction between each outcome measure. Five minutes of rest will be given between isokinetic tests to allow for machine set-up and instructions. One minute of rest will be given between each isokinetic speed, with three speeds tested for the hip (30°, 60°, and 120° per second) and knee (60°, 180°, and 300° per second) muscles.
Participants will be followed for 2 years, with 6-month follow-up calls to track injury status. Details on type of injury, location of injury, and time lost to work will be collected.
- Conditions
- Occupational Injuries, Heat Stress, Leg Injury, Back Injuries
- Being tested
- Rapid Heat Condition, Gradual Heat Condition
- Keywords
- firefighter, musculoskeletal, slip, trip, fall
- Medical subject headings
- Occupational Injuries, Heat Stress Disorders, Leg Injuries, Back Injuries
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Rapid Heat ConditionOther
The heat condition is the intervention. Personal protective equipment will be used to create the rapid heat stress condition, resulting in a rapid rise in core temperature. This will be in combination with the physiological heat produced by the treadmill protocol.
Gradual Heat ConditionOther
The gradual heat condition is the control. Physiological heat will be produced by exercise on a treadmill, and light exercise clothing will help moderate the rise in core temperature.
| Study group | Role | What they receive |
|---|---|---|
| Rapid Heat Stress | Experimental | Participants in the rapid heat stress arm will perform an exercise protocol on a treadmill in a hot, humid environment while wearing firefighter protective gear. This results in an uncompensable heat environment with a rapid increase in core temperature. Receives: Other: Rapid Heat Condition |
| Gradual Heat Stress | Active comparator | Participants in the rapid heat stress arm will perform an exercise protocol on a treadmill in a hot, humid environment while wearing light exercise clothing. This results in an uncompensable heat environment but with a gradual increase in core temperature. Receives: Other: Gradual Heat Condition |
What is being measured
The primary outcome is the main question the study is designed to answer.
Forward-Step-Down Test
a step-down task that is performed off a 20 cm box. Five repetitions are performed to give one score (minimum score 0, maximum score 6). A higher score is worse.
Measured: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).
Y-Balance Test
A dynamic balance test that is performed on the dominant leg, reaching in the anterior, posteromedial, and posterolateral directions. The length of reach is standardized to participants' leg length. A higher score is better, with 0 being the minimum distance and the maximum distance in anterior reach being 126cm, and the maximum posteromedial and posterolateral directions being 149cm.
Measured: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).
Firefighter Specific Functional Balance Test
A dynamic balance test performed by stepping down from a 15cm box, walking across a low beam (4cm high), and stepping up onto a 10cm box, turning around, and returning to the original box. 8 Trials are performed. In 4 trials, a bar is placed at 75% of the participant's height for them to negotiate while on the beam. A faster time with fewer errors is better.
Measured: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).
Knee Flexor/Extensor Isokinetic Test
Knee flexor/extensor isokinetic strength will be tested at 60°, 180°, and 300° per second from the seated position with 5, 10, and 10 concentric contractions for each speed. A higher reading of strength is better.
Measured: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).
Hip Abductor/Adductor Isokinetic Test
Hip abductor/adductor strength will be tested at 30°, 60°, and 120° per second from the standing position. A higher reading of strength is better.
Measured: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).
Secondary outcomes (1)
Injury Occurrence
Participants will be contacted after sessions 1-4 to follow up on occurrence of musculoskeletal injuries, with 0 representing no injury and numerical values indicating presence of injury.
Measured: 6 months, 12 months, 18 months, 24 months after session 4.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted5 Jun 2024
- Study start7 Jan 2025
- Primary completion7 Nov 2025
- Study completion7 Nov 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (27)Papers the sponsor has linked to this study.
- Other trials for Occupational InjuriesStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- randomized crossover
- Masking
- None (open label)
- Enrolment
- 26 participants (actual)
Sponsor and investigators
- Lead sponsor
- Louisiana State University Health Sciences Center Shreveport
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Erin McCallister, DPT, Principal investigator, LSUHSC-Shreveport
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06442956
- Sponsor's protocol ID
- STUDY00002549
- Status last verified
- Mar 2026
- First submitted
- 29 May 2024
- Last updated
- 30 Mar 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Ainsworth BE, Haskell WL, Whitt MC, Irwin ML, Swartz AM, Strath SJ, O'Brien WL, Bassett DR Jr, Schmitz KH, Emplaincourt PO, Jacobs DR Jr, Leon AS. Compendium of physical activities: an update of activity codes and MET intensities. Med Sci Sports Exerc. 2000 Sep;32(9 Suppl):S498-504. doi: 10.1097/00005768-200009001-00009.
PubMed 10993420Brown MN, Char RMML, Henry SO, Tanigawa J, Yasui S. The effect of firefighter personal protective equipment on static and dynamic balance. Ergonomics. 2019 Sep;62(9):1193-1201. doi: 10.1080/00140139.2019.1623422. Epub 2019 Jun 17.
PubMed 31204598Cheung SS, McLellan TM. Influence of hydration status and fluid replacement on heat tolerance while wearing NBC protective clothing. Eur J Appl Physiol Occup Physiol. 1998;77(1-2):139-48. doi: 10.1007/s004210050312.
PubMed 9459534Cheung SS, McLellan TM. Comparison of short-term aerobic training and high aerobic power on tolerance to uncompensable heat stress. Aviat Space Environ Med. 1999 Jul;70(7):637-43.
PubMed 10416998Cheung SS, McLellan TM, Tenaglia S. The thermophysiology of uncompensable heat stress. Physiological manipulations and individual characteristics. Sports Med. 2000 May;29(5):329-59. doi: 10.2165/00007256-200029050-00004.
PubMed 10840867Coehoorn CJ, Neary JP, Krigolson OE, Service TW, Stuart-Hill LA. Firefighter salivary cortisol responses following rapid heat stress. J Therm Biol. 2022 Aug;108:103305. doi: 10.1016/j.jtherbio.2022.103305. Epub 2022 Aug 7.
PubMed 36031202Coehoorn CJ, Patrick Neary J, Krigolson OE, Stuart-Hill LA. Firefighter pre-frontal cortex oxygenation and hemodynamics during rapid heat stress. Brain Res. 2023 Jan 1;1798:148156. doi: 10.1016/j.brainres.2022.148156. Epub 2022 Nov 4.
PubMed 36343724Colburn D, Russo L, Burkard R, Hostler D. Firefighter protective clothing and self contained breathing apparatus does not alter balance testing using a standard sensory organization test or motor control test in healthy, rested individuals. Appl Ergon. 2019 Oct;80:187-192. doi: 10.1016/j.apergo.2019.05.010. Epub 2019 Jun 18.
PubMed 31280804Ftaiti F, Grelot L, Coudreuse JM, Nicol C. Combined effect of heat stress, dehydration and exercise on neuromuscular function in humans. Eur J Appl Physiol. 2001 Jan-Feb;84(1-2):87-94. doi: 10.1007/s004210000339.
PubMed 11394259Gagge AP, Stolwijk JA, Hardy JD. Comfort and thermal sensations and associated physiological responses at various ambient temperatures. Environ Res. 1967 Jun;1(1):1-20. doi: 10.1016/0013-9351(67)90002-3. No abstract available.
PubMed 5614624Games KE, Winkelmann ZK, McGinnis KD, McAdam JS, Pascoe DD, Sefton JM. Functional Performance of Firefighters After Exposure to Environmental Conditions and Exercise. J Athl Train. 2020 Jan;55(1):71-79. doi: 10.4085/1062-6050-75-18. Epub 2019 Dec 26.
PubMed 31876454Hewett TE, Ford KR, Hoogenboom BJ, Myer GD. Understanding and preventing acl injuries: current biomechanical and epidemiologic considerations - update 2010. N Am J Sports Phys Ther. 2010 Dec;5(4):234-51.
PubMed 21655382Lopes TJA, Simic M, Myer GD, Ford KR, Hewett TE, Pappas E. The Effects of Injury Prevention Programs on the Biomechanics of Landing Tasks: A Systematic Review With Meta-analysis. Am J Sports Med. 2018 May;46(6):1492-1499. doi: 10.1177/0363546517716930. Epub 2017 Jul 31.
PubMed 28759729Nascimento LR, Teixeira-Salmela LF, Souza RB, Resende RA. Hip and Knee Strengthening Is More Effective Than Knee Strengthening Alone for Reducing Pain and Improving Activity in Individuals With Patellofemoral Pain: A Systematic Review With Meta-analysis. J Orthop Sports Phys Ther. 2018 Jan;48(1):19-31. doi: 10.2519/jospt.2018.7365. Epub 2017 Oct 15.
PubMed 29034800McCallister E, Flower D. Can the forward-step-down test be used reliably in the clinical setting to assess movement changes resulting from maximal exertion? A pilot study. Internet Journal of Allied Health Sciences and Practice. 2020; 18(4).
Study at a glance
From the registry record, last updated by the sponsor on 30 Mar 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Impact of Rapid Heat Stress on Firefighters' Strength, Dynamic Balance, and Movement Quality
- ClinicalTrials.gov ID
- NCT06442956
- Acronym / sponsor ID
- STUDY00002549
- Conditions
- Occupational Injuries, Heat Stress, Leg Injury, Back Injuries
- Keywords
- firefighter, musculoskeletal, slip, trip, fall
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 26 participants (actual)
- Lead sponsor
- Louisiana State University Health Sciences Center ShreveportUniversity, hospital or other
- Study start
- 7 Jan 2025 (actual)
- Primary completion
- 7 Nov 2025 (actual)
- Study completion
- 7 Nov 2025 (actual)
- First posted
- 5 Jun 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study will examine the effect of heat stress on factors that influence musculoskeletal injury risk in firefighters. Participants will attend 4 data collection sessions. 1: informed consent, screening, and familiarization. 2: pre-tests (strength, balance, and movement quality). 3: heat stress (rapid or gradual) followed by post-tests (strength, balance, and movement quality). 4: heat stress (rapid or gradual) followed by post-tests.
Detailed description
This study utilizes a crossover design, with participants acting as their own controls and participating in both the control (gradual uncompensable heat) and experimental (rapid heat stress (RHS)) conditions. The independent variable is the type of heat stress (uncompensable or rapid). The dependent variables are: peak concentric muscle torque (hip abductors, hip adductors, knee flexors, knee extensors), dynamic balance (Y-Balance Test, Firefighter-Specific Functional-Balance Test (FFSFBT)), and frontal plane movement quality (Forward-Step-Down Test (FSDT)). These will be measured three times, once during pre-testing and twice during post-testing as described below.
The study will consist of four visits. Visit one will be the informed consent and familiarization to the outcome measures. Participants will be educated on filling out the 24-hour food/drink diary, and asked to standardize their diet as close as possible to this record the 24 hours before visits 2, 3, and 4. Injury history and demographic data will be collected at visit 1.
Visit two will be the pre-test data collection, which will occur at approximately 22°C. Participants will complete all outcome measures (torque, balance, movement quality measures). Body composition will also be measured in the BodPod at this time.
Before visits 2, 3, and 4, participants will follow the safety guidelines outlined below to ensure proper hydration:
- 48 hours before: no heat stress (will contact participant to determine if they have been called out to a live fire. Data collection will be postponed if so)
- 24 hours before: no alcohol consumption, no energy drink consumption (normal coffee/tea is allowed)
- 24 hours before: no physical activity (exercise or vigorous play)
- 24 hours before: drink 3.7L of total water to make sure to be well-hydrated
- 2 hours before: eat last meal
Visits three and four will consist of a steady-state treadmill protocol inside the environmental chamber (37-38°C, 50% humidity) followed by post-test measures. During either session three or four, the participant will don his/her firefighting gear (jacket, pants, hood, boots, gloves) and perform the treadmill test with the gear on. This is the RHS trial and will be denoted GEAR. In the other session, the participant will wear exercise clothes (shirt and shorts) plus a weighted backpack to replicate the weight of the gear. This is the gradual uncompensable heat stress trial and will be denoted NOGEAR. The order of the GEAR and NOGEAR sessions will be randomized and counterbalanced to prevent crossover effects.
Upon arrival for the pre-testing visit (session two), participants will be measured for height using a stadiometer and weight. Body composition will be measured once with the BodPod (Cosmed, USA). They will warm up for five minutes on an exercise bike or treadmill then proceed with taking the outcome measures.
Upon arrival for visits three and four, participants will be weighed again. A urine sample will be collected to assess hydration status. They will swallow the core temperature (Tc) capsule 40-45 minutes prior to the start of the session using a small amount of 20°C water, with no further water ingestion throughout the protocol to avoid artificially lowering Tc. Participants will be fit with the Equivital EQLife Monitor (Equivital, NY) system to record heartrate (HR) and Tc. They will then perform the treadmill protocol, and post-test measures will be completed immediately following the cessation of the treadmill test with removal of their gear. They will be weighed following exercise to determine changes in body weight due to sweating.
Sessions three and four will be separated by at least seven days to reduce the influence of heat acclimatization and fatigue. Continuous monitoring of Tc and HR will help ensure participant safety.
The treadmill exercise protocol begins with a graded approach to reach aerobic steady state. The treadmill protocol includes an initial five-minute stage at 3 miles per hour and a 0% grade, followed by increases in percent grade of 4% at minute 5 and 8% at minute 10 and continued throughout the test. Following the final planned incremental increase in treadmill incline, the incline will then be adjusted to ensure that the subject remains at steady-state for the duration of the protocol, defined by a respiratory exchange ratio between 0.9-0.99 using the lab's metabolic cart (Parvomedics, USA). HR, rating of perceived exertion (RPE), thermal comfort, and thermal sensation will be recorded at each 0.5°C interval. The treadmill test will be stopped when participants either reach a Tc of 39°C or a volitional maximum (participant is unable to continue exercise). The investigators will also halt the test if signs of excessive heat stress are present (unsteady gait, confusion, dizziness, slurred speech, etc.) Should the participant not meet either termination criteria, there will be a 50 minute time limit for the treadmill protocol for the GEAR condition and 2 hour limit for the NOGEAR condition. Both GEAR and NOGEAR sessions will begin with the same treadmill test.
Following the treadmill test, the participants will complete the post-test outcome measures. These consist of isokinetic torque of the hip abductors and adductors, isokinetic torque of the knee flexors and extensors, the Y-Balance Test, the FFSFBT, and FSDT. Participants will doff their gear immediately following cession of the treadmill test. For unilateral tests, the dominant leg will be recorded and used for these tests; this is the leg used to kick a ball. Outcome measure order will be standardized for each participant with testing order based on primary outcomes and difficulty of each test. The FSDT will be performed first, as this is the primary outcome and previous research showed that recovery after a maximal exertion stimulus happens quickly. The FFSFBT will be performed next, followed by the Y-Balance Test. Isokinetic testing will be last due to the fatiguing nature of this testing. Hip muscles will be tested first, followed by thigh muscles. Three minutes will be allotted for rest and instruction between each outcome measure. Five minutes of rest will be given between isokinetic tests to allow for machine set-up and instructions. One minute of rest will be given between each isokinetic speed, with three speeds tested for the hip (30°, 60°, and 120° per second) and knee (60°, 180°, and 300° per second) muscles.
Participants will be followed for 2 years, with 6-month follow-up calls to track injury status. Details on type of injury, location of injury, and time lost to work will be collected.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- randomized crossover
| Arm | Type | Receives |
|---|---|---|
| Rapid Heat Stress | Experimental | Other: Rapid Heat ConditionParticipants in the rapid heat stress arm will perform an exercise protocol on a treadmill in a hot, humid environment while wearing firefighter protective gear. This results in an uncompensable heat environment with a rapid increase in core temperature. |
| Gradual Heat Stress | Active comparator | Other: Gradual Heat ConditionParticipants in the rapid heat stress arm will perform an exercise protocol on a treadmill in a hot, humid environment while wearing light exercise clothing. This results in an uncompensable heat environment but with a gradual increase in core temperature. |
Who may qualify
- Ages
- 18 to 57 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (2 listed)
- professional firefighter
- healthy per the Physical Activity Readiness Questionnaire+ screening
Key exclusion criteria (4 listed)
- unable to swallow core temperature capsule
- unable to follow pre-testing hydration criteria
- musculoskeletal injury in the past 3 months that limits ability to perform outcome measures
- females with known pregnancy (risk of hyperthermia to fetus)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Rapid Heat ConditionThe heat condition is the intervention. Personal protective equipment will be used to create the rapid heat stress condition, resulting in a rapid rise in core temperature. This will be in combination with the physiological heat produced by the treadmill protocol. | Other | Rapid Heat Stress |
| Gradual Heat ConditionThe gradual heat condition is the control. Physiological heat will be produced by exercise on a treadmill, and light exercise clothing will help moderate the rise in core temperature. | Other | Gradual Heat Stress |
Primary outcome
Forward-Step-Down Test
Time frame: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).
a step-down task that is performed off a 20 cm box. Five repetitions are performed to give one score (minimum score 0, maximum score 6). A higher score is worse.
Y-Balance Test
Time frame: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).
A dynamic balance test that is performed on the dominant leg, reaching in the anterior, posteromedial, and posterolateral directions. The length of reach is standardized to participants' leg length. A higher score is better, with 0 being the minimum distance and the maximum distance in anterior reach being 126cm, and the maximum posteromedial and posterolateral directions being 149cm.
Firefighter Specific Functional Balance Test
Time frame: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).
A dynamic balance test performed by stepping down from a 15cm box, walking across a low beam (4cm high), and stepping up onto a 10cm box, turning around, and returning to the original box. 8 Trials are performed. In 4 trials, a bar is placed at 75% of the participant's height for them to negotiate while on the beam. A faster time with fewer errors is better.
Knee Flexor/Extensor Isokinetic Test
Time frame: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).
Knee flexor/extensor isokinetic strength will be tested at 60°, 180°, and 300° per second from the seated position with 5, 10, and 10 concentric contractions for each speed. A higher reading of strength is better.
Hip Abductor/Adductor Isokinetic Test
Time frame: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).
Hip abductor/adductor strength will be tested at 30°, 60°, and 120° per second from the standing position. A higher reading of strength is better.
1 secondary outcome
Injury Occurrence
Time frame: 6 months, 12 months, 18 months, 24 months after session 4.
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 30 Mar 2026.
- Background: PubMed 10993420Ainsworth BE, Haskell WL, Whitt MC, Irwin ML, Swartz AM, Strath SJ, O'Brien WL, Bassett DR Jr, Schmitz KH, Emplaincourt PO, Jacobs DR Jr, Leon AS. Compendium of physical activities: an update of activity codes and MET intensities. Med Sci Sports Exerc. 2000 Sep;32(9 Suppl):S498-504. doi: 10.1097/00005768-200009001-00009.
- Background: PubMed 31204598Brown MN, Char RMML, Henry SO, Tanigawa J, Yasui S. The effect of firefighter personal protective equipment on static and dynamic balance. Ergonomics. 2019 Sep;62(9):1193-1201. doi: 10.1080/00140139.2019.1623422. Epub 2019 Jun 17.
- Background: PubMed 9459534Cheung SS, McLellan TM. Influence of hydration status and fluid replacement on heat tolerance while wearing NBC protective clothing. Eur J Appl Physiol Occup Physiol. 1998;77(1-2):139-48. doi: 10.1007/s004210050312.
- Background: PubMed 10416998Cheung SS, McLellan TM. Comparison of short-term aerobic training and high aerobic power on tolerance to uncompensable heat stress. Aviat Space Environ Med. 1999 Jul;70(7):637-43.
- Background: PubMed 10840867Cheung SS, McLellan TM, Tenaglia S. The thermophysiology of uncompensable heat stress. Physiological manipulations and individual characteristics. Sports Med. 2000 May;29(5):329-59. doi: 10.2165/00007256-200029050-00004.
- Background: PubMed 36031202Coehoorn CJ, Neary JP, Krigolson OE, Service TW, Stuart-Hill LA. Firefighter salivary cortisol responses following rapid heat stress. J Therm Biol. 2022 Aug;108:103305. doi: 10.1016/j.jtherbio.2022.103305. Epub 2022 Aug 7.
- Background: PubMed 36343724Coehoorn CJ, Patrick Neary J, Krigolson OE, Stuart-Hill LA. Firefighter pre-frontal cortex oxygenation and hemodynamics during rapid heat stress. Brain Res. 2023 Jan 1;1798:148156. doi: 10.1016/j.brainres.2022.148156. Epub 2022 Nov 4.
- Background: PubMed 31280804Colburn D, Russo L, Burkard R, Hostler D. Firefighter protective clothing and self contained breathing apparatus does not alter balance testing using a standard sensory organization test or motor control test in healthy, rested individuals. Appl Ergon. 2019 Oct;80:187-192. doi: 10.1016/j.apergo.2019.05.010. Epub 2019 Jun 18.
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- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Erin McCallister, DPT principal investigator
LSUHSC-Shreveport
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Rapid Heat Condition and Gradual Heat Condition in people with Occupational Injuries and Heat Stress, run by Louisiana State University Health Sciences Center Shreveport at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 30 Mar 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Forward-Step-Down Test (time frame: Familiarization trials (session 1, recruitment); pre-testing (baseline, session 2 (approximately day 7)); post-control and post-experimental sessions (session 3 (approximately day 14) & 4 (approximately day 21)).). The study lists 5 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT06442956, which also lists 27 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 30 Mar 2026.