Graduation Year

2014

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Education and Psychological Studies

Major Professor

Candi Ashley, Ph.D.

Co-Major Professor

Rebecca Lopez, Ph.D.

Committee Member

Marcus Kilpatrick, Ph.D.

Keywords

beverage temperatures, ice slushy, precooling

Abstract

Precooling is a method used to decrease initial pre-exercise core temperature in order to facilitate a greater margin for heat production before a maximum core temperature is reached. The purpose of this study was to examine the differences in physiological and perceptual effects of precooling using beverages of three different temperatures: room temperature beverage (24.88 ± 1.13°C), cold beverage (6.15 ± 3.16°C) and ice slushy (-1.61 ± 0.45°C) in a hot environment (27.88 ± 0.72°C and 35.36 ± 0.83°C for wet globe bulb temperature and dry bulb temperature respectively). For all trials the environmental temperature was set to 35°C with 56% rh.

For this study, 10 physically active females (age= 23.7 ± 2.26 years, height=1.74 ± 0.23 m, weight=66.27 ± 0.92 kg, BMI=24.14 ± 2.63 kg/m2, body fat= 22.99 ± 2.37% and VO2 max= 43.61 ± 4.78 ml/kg/min) participated in the study. On three separate occasions participants precooled via beverage consumption over a 30-minute period with a 5-minute rest period before beginning a 45-minute interval treadmill protocol. Following exercise, participants then re-cooled for 15 minutes. Each subject precooled and re-cooled with all three beverages at their respective temperature. Treatments were randomized.

There were no significant differences found for TGI during precooling, exercise or re-cooling Mean HR and mean TSK during precooling were significantly lower in the ice slushy trial as compared to the room temperature trial (HR = 75.7 ± 15.7 and 80.1 ± 16.4 bpm; respectively, p < 0.05 ; TSK = 34.47 ± 0.74 and 34.21 ± 0.92ºC; respectively, p < 0.05). There was also a significant difference in thermal sensation during precooling among all three beverage temperatures (Thermal sensation = 4.7 ± 0.7, 4.5 ± 0.7 and 4.0 ± 0.7; for room, cold, and ice slushy respectively, p < 0.05). Mean thirst sensation for ice slushy was also significantly lower during precooling when compared to cold (p < 0.05) and room temperature beverages (p < 0.05). Mean thirst sensation was also significantly lower during exercise for ice slushy compared to cold (p < 0.05) and room temperature (p < 0.05) (precooling thirst sensation= 2.3 ± 1.0, 2.1 ± 1.1 and 1.6 ± 1.0; exercise 4.1 ± 2.0, 4.5 ± 1.7 and 3.2 ± 1.6 for room, cold and ice slushy respectively). During re-cooling mean thirst sensation was significantly lower for ice slush as compared to room temperature (p < 0.05).

Results from the current study suggest that precooling with an ice slushy as compared to a cold or room temperature beverage had little to no effect on TGI and a small effect on HR and TSK during precooling. Although, precooling with an ice slushy appeared to be effective at decreasing perceptual measurements.

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