Load carriage induced alterations of pulmonary function

Load carriage systems supported by the trunk have been shown to decrease certain indices of pulmonary function. We investigated the hypothesis that these pulmonary function reductions are directly related to the backpack load carrier due to the mechanical constraint to imposes on the thoracic cage. To investigate this hypothesis, 5 young males with no pulmonary disorders were tested while standing upright carrying well-fitted 0, 10 or 30 kg loaded U.S. Army ALICE backpacks. Forced vital capacity (FVC), forced expiratory volume (FEV₁) and 15 s maximal voluntary ventilation (MVV₁₅) were measured. With increasing load, FVC and FEV₁ progressively decreased reaching 6 and 6.7% decrements (p < 0.05), respectively, with the 30 kg load. The MVV₁₅ was decreased (p <0.05) by about 8.4% with the 10 kg load, but did not demonstrate any further decrement with the 30 kg load. Analysis of flow-volume loops obtained with the 0 and 30 kg loads showed that the reduction of FVC was not associated with any decrement of peak inspiratory or expiratory flows. These results indicate a limitation on the ventilatory pump caused by load carriage which is directly related to the load carried and characteristic of restrictive disease of the respiratory system (reduced FVC and FEV₁ with no decrement in FEV₁/FVC).