2007, Piran, Slovenia

Occupational Thermal Problems
HORSEBACK MUSTERING IN NORTHERN AUSTRALIA: THE
PHYSIOLOGICAL AND COGNITIVE EFFECTS.
Nigel A.S. Taylor 1 , Joanne N. Caldwell 1 , Rodd Dyer 2
1
Human Performance Laboratories, University of Wollongong, Wollongong, Australia
2
Meat and Livestock Australia, Livestock Production Innovation, Brisbane, Australia
Contact person: nigel_taylor@uow.edu.au
INTRODUCTION
The hottest months encountered on northern Australian cattle stations are from September to
November, where the climate is both hot and dry, and it is during these months that horseback
cattle mustering occurs. Stockmen wear clothing that restricts heat loss (collared shirts and
long trousers), yet protective helmets have recently been introduced into the cattle industry
(AS/NZS 3838:2006), as part of the increasing occupational health and safety responsibilities
of pastoral companies. Anecdotal evidence points to the possibility that protective helmets
may increase the probability of stockmen developing heat illness, or experiencing reduced
workplace performance. Herein, we describe the working and thermal environment on these
cattle stations, and provide an overview of the metabolic demands, and the concurrent
physiological and cognitive strain encountered during horseback mustering in a hot-dry
environment, whilst stockmen wore an equestrian helmet (Taylor and Caldwell, 2007). In
subsequent investigations, we evaluated heat penetration through various forms of headwear
(Caldwell and Taylor, 2007), and completed laboratory-based trials in which the
physiological impact of an equestrian helmet, relative to the traditional felt hat, was evaluated
(Caldwell et al., 2007).
METHODS
Data for the climatic conditions (Bureau of Meteorology, Australia) and the working
environment (clothing insulation, skin surface area coverage, riding velocity, work rates and
physiological responses) were collected from field observations (Victoria River Downs
station; Figure 1). The latter were collected across a broad range of climatic and working
conditions (November), using male and female stockmen from four cattle stations. These
stations have an average size of 2,350 km 2 and carry in excess of 22,000 cattle, and are
situated 320-590 km to the south of Katherine (Australia), or approximately 6-7 o above the
Tropic of Capricorn. The climate of this region is tropical in summer, due to the strong
monsoon season. However, during spring, the climate is much hotter and much drier, and this
season was to focus for this project.
Thirty-eight sets of heart rate data were obtained (30-sec intervals; Polar Electro Sports
Tester, Finland), including 27 mustering trials, from which were derived the oxygen uptake
and metabolic heat production associated with mustering. Heart rates were previously
calibrated (N=6) against simultaneous measures of oxygen uptake and carbon dioxide
production.
In addition, sixteen stockmen participated in eighteen horseback trials (wearing helmets;
Figure 1), which involved complete instrumentation for core (gastrointestinal capsule (Jonah);
VitalSense, Mini Mitter Co. Inc, OR, U.S.A.), skin and clothing temperatures (MSR data
logger, Prospective Concepts AG, Switzerland). Trials varied in duration, but averaged
approximately 5 hours. Physiological data were recorded continuously, with cognitive
function and psychophysical tests performed before and after each trial. 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). Following the
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