A group of Australian researchers investigated the effect of ingesting ice slurry (i.e. drinking a fruitflavoured
ice slushie) on running performance. Of particular interest was whether ingesting an ice
slushie would increase endurance (i.e. time subjects could run before reaching exhaustion).

EXTRACT – from the research paper
Ten healthy males (age = 28 T 6 yr, height = 178.9 T 6.3 cm, body mass = 79.9 T 11.2 kg, sum
of nine skinfolds = 92.8 T 41.4 mm, V˙ O2max = 56.4 T 4.7 mLIkgj1Iminj1) volunteered for this
Subjects were considered moderately active, participating in recreational sport, had no
previous history of heat illness, and were without injuries. Subjects provided written informed
consent before study commencement. The study procedures were approved by the Edith
Cowan University’s Human Research Ethics Committee.
Throughout the study, subjects were asked to keep stable their normal lifestyle activities,
including physical activity and nutritional habits. On the day before each trial, subjects were
asked to eat at least 6 g carbohydrate per kilogram body weight and the same pretrial meal on
the day of the experimental trials (providing at least 1 g carbohydrate per kilogram). They were
also asked to consume at least 2 L of fluid on this day and 400 mL of fluid during the meal
consumed just before the experimental trials.
In the 24-h period before the trials, subjects were asked to avoid strenuous exercise, as well as
the consumption of alcohol, caffeine, nonsteroidal anti-inflammatory drugs, or nutritional
supplements. Before the experimental trials were completed, subjects performed a
familiarization trial involving running to exhaustion at the subject’s previously determined VT1
running speed in the same hot environment as the experimental trials. Within 5–14 d after this
familiarization trial, subjects completed the first of two experimental trials on a treadmill, running
to exhaustion at their VT1 running speed after ingesting either ice slurry (j1-C) or cold water (4-
C). We chose a 4-C temperature for our control drink because this is the typical temperature of
drinks found in conventional refrigeration units. Subjects completed their assigned conditions in
a counterbalanced and random order, at the same time of day, separated by 5–20 d. For each
trial, the subjects wore the same exercise clothing.

(a) What type of study has been conducted here?
(b) What is the response variable and what type of variable is it?
(c) How has comparison been used in the study?
(d) How has randomization been used in the study?
(e) Give one example of a known source of variability that the researchers controlled for in their
study design.
(f) The researchers reported a mean increase of 9.5 minutes in running time until exhaustion after
drinking an ice slushy. Comment on the precision in this estimate.
(g) To what population, if any, could the results of this study be generalized?