Page 73 - Journal of Special Operations Medicine - Summer 2016

Table 1 Subjects’ Demographic Data
Subjects, No. Sex (M:F) Age (years) Height (cm) Weight (kg) Vo (mL/kg/min) Body Fat (%)
2max
12 12:0 25.42 ± 2.84 178.9 ± 7.92 78.25 ± 9.61 57.96 ± 1.96 10 ± 0.03
Values are given mean ± SD unless otherwise indicated. F, female; M, male; Vo , maximal oxygen consumption.
2max
session, subjects wore a novel cooling garment and mil- were captured continuously using the CorTemp Data
itary Airmen Battle Uniform (ABU). The cooling gar- Recorder. Perceived exertion was assessed every 2 min-
ment consisted of a custom-designed, form-fitting shirt utes using the 6 (very, very light) to 20 (very, very hard)
made from moisture-wicking fabric with a pocket over graded scale. Capillary blood lactate level was assessed
18
the chest and back for the placement of cooling cryo- with the Lactate Pro Blood Lactate Test Meter within 3
therapy pads. Two hours prior to each testing session, minutes of completing the shuttle test.
subjects were asked to swallow a core body temperature
pill (CorTemp Core Body Temperature Sensor; HQ Inc., Statistical Analysis
http://www.hqinc.net) with a glass of tepid water. Sub- Analysis was performed using SPSS software for Win-
jects returned to the laboratory 72 hours after each test dows (version 19; IBM, https://www.ibm.com). Means
to confirm that the core body temperature sensor was and standard deviations were calculated. Differences
properly expelled from the digestive tract. were assessed using a two-factor (insert  time), re-
peated measures analysis of variance. When a signifi-
During the first and second testing sessions, subjects cant F ratio was obtained, paired t tests were used to
completed a 70-minute, 22.7kg-weighted treadmill walk- isolate differences among treatment means. Pearson
ing test. One session was performed with the cooling in- correlations were used to evaluate associations among
serts (“loaded”) and one session was completed without variables. An α of p ≤ .05 was considered statistically
the cooling inserts (“unloaded”). Treatment order was significant.
counterbalanced by the subjects to minimize order effect.
First, subjects were fitted with a 22.7kg weighted vest Results
(Better Fitness, Inc., https://www.betterfitnessproducts.
com) and heart rate monitor with chest strap (POLAR This study examined the effects of a cooling shirt on
®
Heart Rate Monitor System; HQ Inc.). Next, subjects core body temperature during physical activity with
performed a 5-minute aerobic warm-up on the tread- a 22.7kg weighted vest with the subject wearing an
mill (Woodway USA, http://www.woodway.com) at 0% ABU. Subjects completed two rigorous physical tests
grade. During the warm-up period, subjects self-selected with and without the Arctic Ease cooling pad inserted
a comfortable walking speed. After the 5-minute warm- into the lightweight shirt with pockets located on the
up, treadmill grade was increased to 2%. Subjects then front, back, and midaxillary: (1) a 70-minute treadmill,
walked continuously for 60 minutes at the pace selected weighted-vest walking test where only core body tem-
during the warm-up. Finally, subjects performed a perature was measured (Figure 3); and (2) a sandbag
5-minute recovery walk at a self- selected treadmill speed. shuttle test that required participants to carry a 22kg
Exercise heart rate and core body temperature were cap- sandbag while wearing a 22.7kg weighted vest for 10
tured continuously using the CorTemp Data Recorder minutes or until reaching volitional fatigue.
(HQ Inc.). Perceived exertion was assessed every 3 min-
utes using the 6 (very, very light) to 20 (very, very hard) The two physiological tests chosen for this study simu-
graded scale. Capillary blood lactate level was assessed lated “real-time” field performance tests typically re-
18
with the Lactate Pro Blood Lactate Test Meter (YSI, Inc.) quired of SOF during training and in the battlefield.
within 3 minutes of the recovery period.

Figure 3 Average core body temperature during 22.7kg
During the third and fourth testing sessions, subjects weighted-vest, treadmill walking trials.
completed a 10-minute lift-and-carry shuttle test wear-
ing a 22.7kg weighted vest. Again, the subjects counter-
balanced loaded and unloaded sessions. Subjects were
instructed to lift a 22kg sandbag from the ground, carry
it 10m, and place it on a platform at a height of 1.45m.
Subjects then returned the sandbag to the floor at the
start line, signifying one complete shuttle. Subjects com-
pleted as many shuttles as possible in 10 minutes while
wearing a 22.7kg weighted vest and POLAR heart rate
monitor. Exercise heart rate and core body temperature

Effect of Cooling Shirt on Core Body Temperature 59