The slushie plus ice towel protocol was compared against a control group with no pre-cooling intervention and a standard cooling technique combining a cold water plunge followed by wearing a cooling jacket. The control group could drink as much cold water as they pleased.
These three study parameters were selected from a group of nine protocols used in the pilot testing before the actual study.
The pilot study protocols for pre-cooling, tested by the University of Melbourne, Australia, are listed below, along with their relative affect (small, moderate and large) on core body temperature.
- A cooling jacket - Participants wore a waist-length cooling jacket, with long sleeves and a hood, constructed with a polyester blend outer shell containing phase change material directly applied to the skin for 30 minutes. (Small)
- Arctic heat vest - Participants wore a rechargeable, waist-length cooling vest constructed with a sport wool outer shell containing a viscose gel directly applied to the skin and recharged every five minutes for 30 minutes. (Small)
- No intervention - These participants were the control group. (Small)
- Iced towels - Participants wore bathroom towels dunked in icy water. The towels were wrung out to extract liquid and three towels were constantly rotated to cover the skin of the torso and legs for 30 minutes. (Small)
- A large volume of cold fluid - Participants ingested 1 liter of cold (39.2 degrees Fahrenheit) sports drink in two boluses at 30 and 45 minutes. They were given 15 minutes to consume each bolus. (Small)
- Small slushie - Participants ingested 500 grams of ice slushie made from sports drink (Gatorade) and were given 30 minutes to consume the bolus with the aid of a straw and spoon to maximize the ingestion of ice. (Small)
- Large slushie - Participants ingested 1 kilogram of a sports drink slushie in two boluses at 30 and 45 minutes. They were given 15 minutes to consume each bolus. (Moderate)
- Plunge - Participants were required to complete whole-body immersion in cold (50 degrees Fahrenheit) water to mid-sternum in an inflatable pool for 10 minutes, followed by 20 minutes of seated rest. Temperature was maintained by the addition of ice and water. (Moderate)
- Combination of a large slushie and iced towels - Following the protocols listed above, in a combined format. (Large)
For the testing protocol, 12 well-trained male cyclists ranging in age from 18 to 35 rode a 46.4-kilometer course (meant to mimic the 2008 Beijing time trial course) that included two climbs at the 12.5 and 37.5 kilometer marks. To more closely mimic riding on a hilly course, industrial fans were used to simulate uphill and downhill wind speeds, and the cooling effects.
The test was conducted in a heat chamber controlled to between 89.6 and 95 degrees Fahrenheit. Humidity was controlled to between 50- and 60-percent relative humidity.
Split times, velocity and power output was collected with key periods of interest being the time to top each climb and the time to finish.