without amputations.
7,18,19
Although participants with ampu-
tations marched at a slower pace than their counterparts,
they may have been working at a similar metabolic rate due
to gait differences observed in previous studies.
20
Metabolic
rate during exercise is an important determinant of core tem-
perature,
21
which may explain the similarities in core tem-
perature between groups in the present study.
Similarly, heavy exercise in hyperthermal conditions at
a constant workload or pace is associated with limited per-
formance time and greater oxygen uptake.
22
In marathons
where an individual is able to self-select pace, pace was
slower by 2% in elite runners and 10% in less-trained run-
ners as the ambient temperature increased.
23
We suspect that
participants in the BMDM inherently adjusted their pace to
mitigate the metabolic-related increase in core temperature,
thereby affecting their time to completion.
Participants without amputations were slightly older on
average than the group with amputations. However, studies
conducted in hot environments have shown that age does
not signi
ficantly affect thermoregulatory function.
24,25
One of the most frequently reported reasons for not
wearing a prosthesis is heat and consequent sweating of
the residual limb.
26,27
We hypothesized that the prosthesis
and liner could inhibit heat dissipation, which might cause
core body temperature to rise more substantially and quickly
with exercise. The variables of BSA and adjusted BSA with
prosthesis liner, however, did not signi
ficantly correlate with
core temperature. Seven of the 9 participants with amputa-
tions had transtibial amputations, which made compari-
sons between levels of amputation, and therefore BSA,
more challenging.
There was no correlation between hydration status and
maximum core temperature (r = 0.09, p = 0.69), consis-
tent with other research conducted in an outdoor environ-
ment.
28,29
Participants in this study lost less than 2% of their
body weight, which is under levels previously reported to
affect core temperature and within the guidelines for hydra-
tion during exercise.
3,30
Previous studies have shown that
adequate
fluid replacement during exercise may help attenu-
ate the rise in core temperature.
31
Unlike this study, how-
ever, many of those studies controlled
fluid intake.
32
It is possible that the relatively mild temperatures during
the BMDM, which ranged from 12 to 23°C, were not in the
hyperthermal ranges tested in other studies that showed sig-
ni
ficant differences between conditions.
22,23
The low relative
humidity of 10 to 25% and average wind speed during the
BMDM ranged 5 to 15 miles per hour most likely assisted
in heat dissipation,
2,3
as well.
The main limitation in this study is the small sample size
and possibility of a type 2 error. The loss of three partici-
pants degraded the ability to detect statistical differences and
required the analyses to be limited in complexity. A larger
sample size would allow analyses that controlled for the
effect of all of the covariates on core temperature during
exercise. To provide a more complete understanding of the
role of hydration and sweat rate in body temperature regula-
tion, future studies should monitor
fluid intake, food intake,
and urination during the event, in addition to weight before
and after. The results are promising, though, in suggesting
future research related to the effect of workload or pace on
core temperature.
The results of this study suggest that people with amputa-
tions may not be at higher risk for heat injury when exercising
at a self-selected pace in moderate conditions. Until conclusive
evidence is accumulated, however, it is prudent for trainers
and military service members to closely monitor this popula-
tion during physical activity to prevent heat injuries. Future
research that is adequately powered is needed to fully investi-
gate the potential differences in core temperature between ser-
vice members with and without amputations during prolonged
exercise. Additional research should be performed in addi-
tional conditions with greater heat stress to validate the pre-
liminary
findings of this study will ensure adequate safety
protocols are developed and procedures are implemented to
decrease risk of heat injury for military service members and
athletes with and without lower limb amputation.
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FIGURE 1.
Maximal core temperature in relation to duration of event in
participants with and without amputation.
MILITARY MEDICINE, Vol. 181, November/December Supplement 2016
64
Core Temperature in Service Members With and Without Traumatic Amputations