The purpose of this study was to assess the energy expenditure associated with load carriage using both a traditional rucksack and a new rucksack design, the AARN rucksack, which incorporates front balance pockets. Nine volunteers walked at 3 km h−1 at various uphill and downhill gradients on a treadmill without a load and carrying a load of 25.6 kg in each of the rucksacks. The oxygen consumption associated with both of the loading conditions was significantly (P < 0.001) higher than that associated with unloaded walking at all downhill gradients tested, although there was no significant difference between the two loading conditions. During the uphill gradients the oxygen consumption associated with the AARN pack was significantly (P < 0.05) lower than that associated with the traditional pack at the 0%, 5%, 10% and 20% gradients. The mean (%) differences at these gradients, expressed in ml · kg−1 · min−1 were 1.18 (9%), 1.45 (8%), 1.76 (8%) and 1.88 (6%), respectively. On average for the whole protocol, the oxygen consumption associated with the AARN rucksack was 5% lower than that associated with the traditional rucksack [mean (SD) 17.28 (7.46) ml · kg−1 · min−1 for the AARN pack and 18.20 (7.84) ml · kg−1 · min−1 for the traditional pack]. The findings of the present study suggest that a load carriage system that allows the load to be distributed between the back and font of the trunk is more appropriate for carrying relatively heavy loads than a system that loads the back only.

methods or result

Ergonomical studies on load carrying up staircases. I. Effect of external load on energy cost and heart rate.

The oxygen consumption associated with unloaded walking and load carriage using two different backpack designs.

Variations of the mechanical energy levels of the body segments, as affected by different backpack loads were investigated, to determine if mechanical energy analyses rather than metabolic measures could be used to evaluate load carriage devices. Six male subjects were required to walk upon a level treadmill at 5·54km/hour while they carried five loads ranging from 15·16 to 33·85kg, in a specially designed backpack. Cinefilm was taken, digitized and filtered. Kinematic data, energy levels of the segments of a 15 member linked-segment model and overall work indices were calculated. Expired air was collected and metabolic cost determined. Results showed that about 1/3 of the mechanical work done by all body segments represents energy exchanges within segments and another 1/3 between segments, the major increase in the mechanical work done was in the load itself and virtually no alternations in gait pattern were made by the subjects to accommodate heavier loads. Some undesirable exchanges of energy were evid...

Mechanical energy analyses of the human during local carriage on a treadmill.

As part of a combined electromyographic, mechanical work and metabolic study of load carriage this research focuses on the optimal load carried by the subject. This study demonstrates the anomalies associated with the definition of optimal load, and shows that it is dependent on whether or not the carrier is given any credit for carrying his own weight as well as that of the load. In many situations it may be important to include the carrier's own body mass in the optimal load equation. This study showed that if the load were body plus backpack the optimal backpack load was found to be quite low (less than 10kg) because the metabolic cosi increased quite rapidly at low loads. On the other hand, if the carrier's mass was ignored there might be an optimum load at 40 kg or higher. Giving partial ‘credit’ for carrying body weight (for example, 50% body mass plus backpack), resulted in an optimum load of about 17 kg. The percentage ‘credit’ given to the body mass itself depends on how important it is that the ...

Metabolic measures to ascertain the optimal load to be carried by man.

To study the influence of weight carrying on the cardiorespiratory system during dynamic exercise (walking) four conditions, i.e., rest, and treadmill exercise at 25, 50, and 75% of the individual VO2max, were combined with weight carrying of 10, 20, and 30 kg. In all experiments oxygen uptake, heart rate and pulmonary ventilation were measured. For each dynamic exercise condition and for the rest condition regression lines are calculated showing the relation between weight load and oxygen uptake, heart rate and pulmonary ventilation. From the slopes of these regression lines it can be seen that in rest (standing position) weight carrying does not influence oxygen uptake, heart rate and pulmonary ventilation. In dynamic exercise oxygen uptake, heart rate and pulmonary ventilation increase linearly with the amount of weight carried. To a large extent this increase is independent of the dynamic work load. In this study it was found that each kilogram extra weight increases oxygen uptake with 33.5 ml/min, heart rate with 1.1 beats/min and pulmonary ventilation with 0.6 l/min. In dynamic work for loads higher than 50% of VO2max the relationship between weight carried and pulmonary ventilation is no longer a linear one. For the subjects studied it is assumed that oxygen consumption per kilogram weight is not different for body weight or extra weight carried.

Ergonomical studies on load carrying up staircases. I. Effect of external load on energy cost and heart rate.

Citations

The oxygen consumption associated with unloaded walking and load carriage using two different backpack designs.

Mechanical energy analyses of the human during local carriage on a treadmill.

Metabolic measures to ascertain the optimal load to be carried by man.

Influence of heavy weight carrying on the cardiorespiratory system during exercise.

Optimum load for carriage by soldiers at two walking speeds on level ground

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