Relationship between energy intake and expenditure during harvesting tasks

The objective of this study was to compare the energy demands of manual harvesting tasks with the associated energy intake of the workers’. Fifty eight workers (29 Chainsaw Operators and 29 Stackers) were assessed in South Africa prior to, and during a ‘normal’ working shift. Habitual dietary analyses showed that the workers were eating less than 56% of the recommended daily allowance and were thus arriving at work with reduced energy stores. 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. The data indicated that the tasks placed ‘moderate-to-heavy’ demands on the workers resulting in a significant imbalance between the energy demands of the tasks and the associated energy intake of the workers. Energy deficits were in excess of 8 000 kJ and workers lost, on average, 2.8% body mass during work while felling and cross-cutting, and 3.6% during stacking