2007, Piran, Slovenia

Personal protective equipment
EXERCISING IN COMBAT ARMOUR AND HELMETS IN HOT-
HUMID CONDITIONS: THE STRAW THAT BROKE THE CAMEL’S
BACK
Joanne N. Caldwell 1 , Lian Engelen 1 , Charles van der Henst 1 , Mark J. Patterson 2 ,
Nigel A.S. Taylor 1
1 Human Performance Laboratories, University of Wollongong, Wollongong, and 2 Defence
Science and Technology Organisation, Melbourne, Australia
Contact person: nigel_taylor@uow.edu.au
INTRODUCTION
Metabolic and external heat sources are equally capable of elevating body core temperature in
individuals working in hot environments. When heat loss avenues are impeded by clothing
and protective equipment, the risk of exertional heat stress is further increased. There are
various work-rest guidance tables available within the literature, some of these have
correction factors for variations in clothing insulation, such that rest periods are lengthened
and work periods shortened when clothing insulation is increased (TBMED 507). However,
there is a paucity of experimental data upon which such modifications may be based. An
absence of such empirical data may result either in an increased risk of exertional heat illness,
or compromised operational capability, if physiological strain is over-estimated (Danielsson
and Bergh, 2005). Therefore, the aim of this project was to assess the impact of wearing such
body armour on physiological and cognitive function in hot-humid conditions.
METHODS
The physiological and cognitive impact of wearing combat body armour was evaluated at
work intensities that represented those associated with an urban patrol in hot-humid
conditions (36°C, 60% relative humidity), with a substantial radiant heat source (infra-red
lamps). Nine physically-active males participated in three, exercise and heat stress trials,
walking for 2.5 h at two intensities (0.56 m.s -1 (1.5 h) and 1.11 m.s -1 )). Trials differed only in
the equipment worn: control trial: disruptive pattern (camouflage) combat uniform with a
cloth hat (clothing mass: 2.05 kg; insulation 0.29 m 2 K.W -1 ); torso armour trial: disruptive
pattern combat uniform plus combat body armour (Aramid-lined vest with ceramic-plate
inserts) covering the chest and back (Hellweg, Australia; 6.07 kg) with a cloth hat (total
ensemble mass: 8.12 kg); and torso armour and helmet trial: disruptive pattern combat
uniform, combat body armour (chest and back) and combat helmet (Aramid construction;
Rabintex Industries Pty. Ltd., Australia (1.29 kg); total ensemble mass: 9.41 kg).
Physiological variables included insulated auditory canal temperature (Edale Instruments Ltd,
Cambridge, U.K.), skin temperatures from eight sites (Type EU, Yellow Springs Instruments
Co. Ltd., Yellow Springs, OH, U.S.A.), heart rate (Polar Electro Sports Tester, Finland), and
gross mass changes (corrected for drinking, urine production and sweat retained within the
clothing and body armour). At 15-min intervals, data were collected for perceived work effort
(15-point Borg scale), thermal sensation and thermal discomfort.
Cognitive function was evaluated using the Mini-Cog rapid assessment battery (Shephard and
Kosslyn, 2005) administered via a personal digital assistant (PDA, PalmOne, Tungsten C,
U.S.A.), following 8-10 h of preliminary training. The following tests were administered at
30-min intervals during each trial: vigilance; three-term reasoning; filtering; verbal working
memory, divided attention and perceptual reaction time.
233