The objective of this study was to examine the impact of four single-bout heating and cooling strategies on warming up and cooling down core body temperature. Heating strategies included: Passive heating in a hot environment (60 min), Active heating (30 min) + passive heating (30 min) in a hot environment, Active heating(60 min) in a hot environment, and Active heating (60 min) at room temperature. Cooling strategies to reduce body core temperature to baseline included: Cool vest (18°C) , Damp neck towel (24°C) combined with arm (i.e. hand, forearm and half of upper arm) cool water immersion (15°C), Combination of both, A control with participant sitting in a thermoneutral room (20°C air temperature) without any additional cooling intervention.
This semi-randomized crossover control trial was performed between September and October 2020. Data collection took place over the course of 5-weeks with 10 subjects, with one data collection session with all subjects per week (hence, 40 trials total). Baseline gastrointestinal temperature (Tgi) was recorded, and the final Tgi at the end of the heating intervention (Part I), was used as the starting temperature for the current study (Part II). Part I focused on assessing the efficacy of different heating strategies (Passive heating in a hot environment (60 min), Active heating (30 min) + passive heating (30 min) in a hot environment, Active heating(60 min) in a hot environment, and Active heating (60 min) at room temperature), aiming to reach a core temperature of 38.5°C during a 60-minute period. Part II focused on cooling the body to a pre-exercise baseline core temperature. Cooling strategies consisted of: 1) Cool vest (18°C) with 500 mL (16 fl oz) ice water consumption, 2) Damp neck towel (24°C) combined with arm (i.e. hand, forearm and half of upper arm) cool water immersion (15°C) and 500 mL (16 fl oz) ice water consumption 3) Combination of cool vest (18°C), damp neck towel (24°C) with arm cool water immersion (15°C), and 500 mL (16 fl oz) ice water consumption or 4) A control with participant sitting in a thermoneutral room (20°C air temperature) without any additional cooling intervention. Thermoneutral water was consumed ad libitum for all interventions in addition to the 500 mL (16 fl oz) ice water consumption for experimental trials (#1-3).
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
OTHER
Masking
NONE
Enrollment
10
Participants performed seated passive heating in 54C conditions
Participants performed 30 minutes of biking exercise in 43C + 30 min of passive seated heating in 54C conditions.
Participants performed 60 minutes of biking exercise in 43C.
Participants performed active heating through biking exercise for 60 minutes at room temperature.
Cool vest (18°C) with 500 mL (16 fl oz) ice water consumption
Damp neck towel (24°C) combined with arm (i.e. hand, forearm and half of upper arm) cool water immersion (15°C) and 500 mL (16 fl oz) ice water consumption
Combination of cool vest (18°C), damp neck towel (24°C) with arm cool water immersion (15°C), and 500 mL (16 fl oz) ice water consumption
A control with participant sitting in a thermoneutral room (20°C air temperature) without any additional cooling intervention.
Community Services Building
Tempe, Arizona, United States
Body core temperature
A portable telemetry system (E-Celsius, BodyCAP, Hérouville Saint-Clair, France) for temperature sensor capsule, with an accuracy of +/- 0.2°C, was used to measure body core temperature.
Time frame: During 60 minute of heating intervention, followed by 60 minutes of cooling intervention.
Skin temperature
Wireless temperature sensors (iButton DS1+2L, Dallas Semiconductor Corp, USA), with an accuracy of ± 0.5°C and a resolution of 0.0625°C, were used to measure Tsk at 20-second intervals. Sensors at four locations (neck, right shoulder, and right shin with all 0.28 weighted coefficient, and left hand with a coefficient of 0.16 to calculate weighted Tsk outcome) as suggested per ISO protocol, held in place at the skin using Opsite transparent film (Opsite Flexigrid, Smith \& Nephew Medical Limited, Hull, England).
Time frame: During 60 minute of heating intervention, followed by 60 minutes of cooling intervention.
Heart rate
Participants wore an elastic chest strap device (Bioharness-3, Zephyr Technology, Annapolis, MD, USA), measuring HR in beats per minute (bpm) at 1-second intervals.
Time frame: During 60 minute of heating intervention, followed by 60 minutes of cooling intervention.
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