The adaptations to fatigue during a repetitive lifting test

Twelve subjects performed a fatiguing repetitive lift in the sagittal plane until exhaustion to discover the effect of fatigue on changes in kinematics, postural stability, and coordination. A load equal to 25% of the subjects' isoinertial lifting capacity was repetitively lifted and lowered at a maximal lifting rate from mid-tibia to waist height. Knee and hip range of motion were significantly decreased, while peak trunk flexion increased at the end of the task. Postural stability decreased and subjects extended their knee, hip and spine earlier in the lifting phase, at the end of the task. Some of these adaptations are indicative of mechanisms that may cause increased loading of the passive tissues of the spine and hence increased risk of injury, while others need to be investigated further.