following morning approximately 2 hours before starting the
event. In previous studies, ingesting the sensor 4 to 6 hours
prior was optimal; however, due to the projected event dura-
tion, a shorter lead-time was chosen to minimize early excre-
tion of the sensor during the event.
14,15
Once ingested, the
sensor telemetrically transmitted core temperature data every
10 seconds to an external receiver worn on the participant
’s
waist. The data were downloaded from the receiver to a
study laptop after the event. Minimum and maximum air
temperature were recorded for the day of the race.
16
Statistical Analysis
Data are presented as mean ± SD. Core temperature data
were processed to provide 5-minute averages for the dura-
tion of the event. The primary outcome variables of interest
were maximal core temperature, time to reach maximal core
temperature, time to 38.3°C, time above 38.3°C, time to
40°C, and time above 40°C. These core temperature levels
were chosen based on risk of heat exhaustion and heat
stroke, respectively.
17
Group temperature means and demo-
graphic data were compared using an independent t test.
Levene
’s test for equality of variance was used to ensure
assumptions of normality were met for the two groups.
Pearson
’s correlations were used to assess the relationship of
maximal core temperature and time above 38.3°C to event
duration, hydration status (USG), BSA, and BMI.
Statistical analyses were conducted using the PASW Sta-
tistics 18 (SPSS Inc, Chicago, Illinois). A priori power cal-
culation suggested that with group sample sizes of 10 each,
there was 80% power to detect a difference of 0.59°C
between groups with signi
ficance level of p < 0.05.
RESULTS
All participants started the BMDM. Two participants (1 trans-
tibial, 1 transfemoral) with amputations did not
finish the
event: one due to prosthesis malfunction and a second
opted to complete the 15.2-mile honorary march due to
pain. Data for these participants were not included in the
analysis. One control group participant
’s temperature reader
malfunctioned rendering the data unusable. As a result, data
from 17 participants (9 control, 8 amputation) were used in
the analyses. The groups were well matched in anthropomet-
rics, with the exceptions that the control group was older
( p = 0.029) and the amputation group was taller ( p = 0.038)
( Table I).
There was no signi
ficant difference in maximal core tem-
perature between the groups ( p = 0.27) (Table II). Nearly
all participants (8 control, 6 amputation) reached the thresh-
old of 38.3°C (Fig. 1). Maximal core temperature for the
amputation group ranged from 38.2 to 38.8°C. For the con-
trol group, maximal core temperature ranged from 38.1 to
39.0°C. No subjects reached 40.0°C. Time spent above the
38.3°C threshold was not signi
ficantly different between
groups (Table II) but varied widely by participant in relation
to the duration of the event.
The control group
finished the event faster than the ampu-
tation group ( p = 0.01). There was no signi
ficant correlation
between event duration and time above 38.3°C or max core
temp (Fig. 1). There were no signi
ficant correlations between
hydration, BSA, and BMI with either maximal core tempera-
ture or time above 38.3°C.
DISCUSSION
The primary objective of this study was to compare changes
in core body temperature in individuals with and without
amputations during a prolonged endurance event. Although
we hypothesized that participants with amputations would
have higher core temperatures than participants without
amputations during the 26.2-mile BMDM, the data collected
did not support this hypothesis. Speci
fically, all metrics were
similar between the two groups, except time to completion.
When walking at similar speeds individuals with amputa-
tions may expend up to 33% more energy than individuals
TABLE I.
Participant Demographics for Participants With and
Without Amputation
With Amputation
(n = 8)
Without Amputation
(n = 9)
Age (Year)
26.1 ± 3.6*
33.3 ± 7.7
Height (cm)
181.9 ± 5.2*
176.4 ± 4.8
Weight (kg)
a
92.3 ± 18.9
84.4 ± 11.2
BMI (kg/m
2
)
a
27.8 ± 4.5
27.2 ± 4.1
BSA Adjusted
b
4.46 ± 0.98
4.14 ± 0.55
Body Fat %
18.0 ± 8.9
19.6 ± 5.5
Muscle Mass (g)
65,996 ± 10,918
63,685 ± 5,629
Fat Mass (g)
18,978 ± 8,527
16,773 ± 6,667
Data are mean ± SD.
a
Weight for amputation group is adjusted to account
for missing limb proportion; adjusted weight used to calculate BMI for
same subjects.
b
BSA for amputation group is adjusted to account for miss-
ing limb proportion. *Signi
ficantly different than control group at p < 0.05.
TABLE II.
Event Measures for Participants With and Without
Amputation
With
Amputation
(n = 8)
Without
Amputation
(n = 9)
Maximum Core Temperature (°C)
38.56 ± 0.23
38.64 ± 0.26
Time to Maximum
Core Temp (Minutes)
390 ± 124
344 ± 143
Time to 38.3°C (Minutes)
293 ± 161
206 ± 178
Time Above 38.3°C (Minutes)
101 ± 83
128 ± 113
USG Postevent
1.021 ± 0.011
1.022 ± 0.008
Weight Loss at End of Event (kg)
1.55 ± 1.12
1.72 ± 1.01
Weight Loss %
1.78 ± 1.32
1.87 ± 1.08
Duration of Event (Hour)
9.6 ± 0.96*
7.9 ± 1.4
Data are mean ± SD. *Signi
ficantly different than control group at p = 0.01.
MILITARY MEDICINE, Vol. 181, November/December Supplement 2016
63
Core Temperature in Service Members With and Without Traumatic Amputations