Improving the energy and fluid balance of workers involved in harvesting tasks

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.