Affiliations: Department of Human Kinetics and Ergonomics, Rhodes
University, Grahamstown, South Africa. Tel.: +27 (46) 6038470; Fax: +27 (46)
6223803; E-mail: [email protected]
Abstract: The objective of this study was to assess the impact of a dietary
and fluid intervention on workers doing heavy manual labour within the forestry
industry. Fifty eight workers (29 Chainsaw Operators and 29 Stackers) were
assessed in South Africa prior to, and during a 'normal' working shift. Body
mass was measured and recorded prior to and on completion of the work shift.
Heart rate responses were measured continuously during work and energy
expenditure was predicted from the heart rate/oxygen uptake relationship
obtained at a post-work progressive step up test completed by each worker.
These data were then compared to the initial study, previously published, in
order to determine whether energy balance, fluid balance and workers'
perceptions where altered by the provision of a dietary and fluid intervention
programme. The data indicated that the relationship between energy expenditure
and energy intake was substantially improved by the provision of food and
fluid. Workers lost, on average, 1.94 kg body mass during work while felling
and cross-cutting and 2.41 kg during stacking. This reduced significantly to a
loss of 0.31 kg and 0.70 kg in the Chainsaw Operators and Stackers respectively
following the introduction of water and food during the work period. Likewise,
the energy deficit was significantly improved due to the introduction of a
nutritional supplement. Pre-intervention the deficit was 8861.8 kJ (Chainsaw
Operators) and 8804.2 kJ (Stackers) while in the post-intervention phase this
deficit was reduced by approximately 50% for both groups of workers.
Keywords: Chainsaw operators, stackers, energy intake, energy expenditure, dehydration