Heat, High-Intensity Interval Training
Conditions
Brief summary
The goal of this repeated measures study is to evaluate acute work rate adjustments during high-intensity interval training (HIIT) in a hot and temperate environment in healthy and active adults when using target heart rate to prescribe the exercise intensity. The main questions it aims to answer are: * Will HIIT based on target heart rate in a hot environment result in increased cardiovascular (i.e., elevated recovery HR) and thermal strain compared to HIIT in a temperate environment? * Will work rate be lowered to a greater extent during HIIT in a hot environment compared to a temperate environment in order to maintain target heart rate? * Will maximal aerobic capacity (V̇O2max) decrease to a greater extent after HIIT in the heat compared to a temperate environment? Procedures: Participants will complete 5 trials on a cycle ergometer. Trial 1 (Control Visit): Participants (n = 7) will have their maximal heart rate and V̇O2max measured in a temperate environment (\ 22 °C, 40% RH). Experimental Trials 2-5: The order of the trials will be counterbalanced and randomly assigned to participants. * 15TEMP: Participants will cycle at 70% of their maximum heart rate for 8 minutes as a warm-up, followed by one round of HIIT. The HIIT protocol consists of 4 minutes at 90% of maximum heart rate followed by 3 minutes at 70% of maximum heart rate, totaling 15 minutes, in a temperate environment (\ 22 °C, 40% RH). After the HIIT session, a graded exercise test will measure V̇O2max. * 15HEAT: Similar to 15TEMP, but participants will perform the HIIT protocol in a hot environment (\ 35 °C, 40% RH). * 43TEMP: Participants will cycle at 70% of their maximum heart rate for 8 minutes as a warm-up, followed by the HIIT protocol repeated four times (4 minutes at 90% of maximum heart rate and 3 minutes at 70% of maximum heart rate), totaling 43 minutes, in a temperate environment (\ 22 °C, 40% RH). * 43HEAT: Similar to 43TEMP, but participants will perform the HIIT protocol in a hot environment (\ 35 °C, 40% RH).
Interventions
BEHAVIORAL15 minutes of high-intensity interval training
Participants completed an 8 min warm-up and 1 round of high-intensity interval training
BEHAVIORAL43 minutes of high-intensity interval training
Participants completed an 8 min warm-up and 5 rounds of high-intensity interval training
OTHERHot environment
Participants exercised in a hot environment, \ 35 °C, \ 40% relative humidity.
OTHERTemperate environment
Participants exercised in a temperate environment, \ 22 °C, \ 40% relative humidity.
Sponsors
University of Alabama, Tuscaloosa
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
OTHER
Masking
NONE
Intervention model description
Participants completed all trials and were compared to themselves.
Eligibility
Sex/Gender
ALL
Age
18 Years to 39 Years
Healthy volunteers
Yes
Inclusion criteria
* Participants were healthy males and females who are 18 to 39 years of age, recreationally active as defined by the American College of Sports Medicine, performing moderate-intensity aerobic exercise 30 min or more per session for at least 3 sessions per week for at least the past 3 months, and free of metabolic, cardiovascular, and renal disease
Exclusion criteria
* Individuals classified as needing medical clearance according to American College of Sports Medicine (ACSM) Guidelines were not allowed to participate. Needing medical clearance is defined by ACSM as 1) not being physically active and having known cardiovascular, metabolic, or renal disease and asymptomatic; 2) not being physically active and having any signs or symptoms suggestive of cardiovascular, metabolic, or renal disease; 3) participating in regular exercise and having known cardiovascular, metabolic, or renal disease and asymptomatic; or 4) participating in regular exercise and having any signs or symptoms suggestive of cardiovascular, metabolic, or renal disease .
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Work rate adjustments | From the first work interval (min 9-12) to the last work interval (min 37-40). | In a hot and temperate environment by how much does work rate need to be adjusted to maintain target heart rate? |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Cardiovascular strain | From the first recovery interval (min 13-15) to the last recovery interval (min 41-43). | In a hot and temperate environment by how much does heart rate in the recovery intervals increase? |
| Thermal Strain | From the first work interval (min 9-12) to the last work interval (min 37-40). | In a hot and temperate environment by how much do rectal temperature and skin temperature increase? |
| Maximal aerobic capacity | The end of the 15 min trials compared to the end of the 43 min trials. | In a hot and temperate environment by how much does maximal aerobic capacity decrease? |
Countries
United States
Outcome results
None listed