Study Design. This is a repeated-measures design where the subjects acted as their own controls. Curvature of the spine, as well as mean trunk and head flexion were noted twice during 21 minutes of load carriage: in rested and fatigued conditions.
Objective. To determine if spinal curvature and posture were affected by mild fatigue in load carriage.
Summary of Background Data. Researchers have found a link between load carriage and low back problems. Changes in gait and posture resulting from load carriage are largely a result of the body's attempt to increase stability.
Methods. Apparently healthy females (n = 25) carried a 9-kg backpack at 1.79 m/s for 21 minutes around a 200-m circuit. The pack had spring-loaded displacement rods intended to measure displacement from the pack to the spine. Subjects were filmed (60 Hz) and displacement data were collected during minute 3 (rested condition) and minute 18 (fatigued condition).
Results. The MANOVA revealed that the thoracic to lumbar region cubic curve significantly increased as subjects fatigued. Rested trunk and head angles were not significantly different from the fatigued condition. Trunk and head angles were not indicative of spinal curvature at 18 minutes; therefore, they may not be the best measures of fatigue during load carriage.
Conclusions. Spine and back health may be adversely affected by load carriage sooner than was previously thought, and it may be important to use spinal curvature as a measure of posture for future load carriage studies.