Evaluation of Various Cooling Systems After Exercise-Induced Hyperthermia.
BACKGROUND
Rapid diagnosis and expeditious cooling of individuals with exertional heat stroke is paramount for survival.


OBJECTIVE
To evaluate the efficacy of various cooling systems after exercise-induced hyperthermia.


METHODS
Crossover study.


METHODS
Laboratory.


METHODS
Twenty-two men (age = 24 ± 2 years, height = 1.76 ± 0.07 m, mass = 70.7 ± 9.5 kg) participated.


METHODS
Each participant completed a treadmill walk until body core temperature reached 39.50°C. The treadmill walk was performed at 5.3 km/h on an 8.5% incline for 50 minutes and then at 5.0 km/h until the end of exercise. Each participant experienced 4 cooling phases in a randomized, repeated-crossover design: (1) no cooling (CON), (2) body-cooling unit (BCU), (3) EMCOOLS Flex.Pad (EC), and (4) ThermoSuit (TS). Cooling continued for 30 minutes or until body core temperature reached 38.00°C, whichever occurred earlier.


METHODS
Body core temperature (obtained via an ingestible telemetric temperature sensor) and heart rate were measured continuously during the exercise and cooling phases. Rating of perceived exertion was monitored every 5 minutes during the exercise phase and thermal sensation every minute during the cooling phase.


RESULTS
The absolute cooling rate was greatest with TS (0.16°C/min ± 0.06°C/min) followed by EC (0.12°C/min ± 0.04°C/min), BCU (0.09°C/min ± 0.06°C/min), and CON (0.06°C/min ± 0.02°C/min; P < .001). The TS offered a greater cooling rate than all other cooling modalities in this study, whereas EC offered a greater cooling rate than both CON and BCU (P < .0083 for all). Effect-size calculations, however, showed that EC and BCU were not clinically different.


CONCLUSIONS
These findings provide objective evidence for selecting the most effective cooling system of those we evaluated for cooling individuals with exercise-induced hyperthermia. Nevertheless, factors other than cooling efficacy need to be considered when selecting an appropriate cooling system.
Combat Protection and Performance, Defence Medical and Environmental Research Institute, Singapore.
Pearl M S
PM
Tan
Combat Protection and Performance, Defence Medical and Environmental Research Institute, Singapore.
Eunice Y N
EY
Teo
Soldier Performance Centre, Singapore Armed Forces.
Noreffendy B
NB
Ali
Soldier Performance Centre, Singapore Armed Forces.|National Healthcare Group Eye Institute, Tan Tock Seng Hospital, Singapore.
Bryan C H
BC
Ang
Soldier Performance Centre, Singapore Armed Forces.
Iswady
I
Iskandar
Combat Protection and Performance, Defence Medical and Environmental Research Institute, Singapore.
Lydia Y L
LY
Law
Combat Protection and Performance, Defence Medical and Environmental Research Institute, Singapore.|Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore.
Jason K W
JK
Lee
D018592:Cross-Over Studies; D017679:Cryotherapy; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology; D018883:Heat Stroke / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D010465:Perception / Q000502:physiology; D005082:Physical Exertion; D013697:Thermosensing; D055815:Young Adult
core temperature; exertional heat stroke; safety