Ventilatory and respiratory muscle function of British Army infantry soldiers is similar to physically active civilians at rest and in response to torso-borne thoracic load carriage activities

Purpose: This study sought to compare ventilatory and respiratory muscle function between infantry soldiers with load carriage (LC) experience and physically active civilians with no LC experience at rest and in response to LC activities.

Methods: Seventeen male British Army infantry soldiers and 14 physically active male civilians completed two trials on separate days (unloaded and donning 25kg). Each trial involved a treadmill 50-minute march (4.8km·h-1, 0% incline) followed by a 2km best effort test. Spirometry and respiratory muscle strength (maximal mouth pressures) were recorded at rest and in response to the march and best effort in both trials. Independent t-tests determined any differences at rest (unloaded), in spirometry and respiratory muscle strength, between the two groups. Three-way mixed-model ANOVAs determined any main effects and interactions with time point (rest, post march and post 2km), group (soldiers and civilian) and condition (unloaded and 25kg) with respiratory muscle strength. Alpha was set at p < 0.05.

Results: Resting spirometry and respiratory muscle strength values were similar (p = 0.322 – 0.658) between the two groups. Significant reductions in maximal expiratory mouth pressure were observed in response to 25kg LC (p = 0.036) when compared to unloaded and with time (p =