Effects of Ankle Plantar Flexion / Dorsiflexion Tilt on Lifting Motions under Instruction to Focus on the Hip Position

Abstract

Previous studies have suggested that verbal instruction focusing on the hip position, such as ‘holding an object with their hips down’, leads to recommended lifting motions （holding objects with knee and hip joints flexed simultaneously）. This study investigated the effectiveness of such instruction with assuming poor flexibility of the lower limb. Sixteen healthy males performed a lifting motion using the Toe-wedge （with the toes higher than the heels）, with verbal instructions focusing on the hip position. Motion analysis revealed that the knee flexion was smaller and the trunk was greatly tilted forward under the Toe-wedge than that under the flat floor condition. Therefore, the individuals with poor lower limb flexibility might be difficult to perform the recommended lifting motion even with instructions focusing on the hip position. This study also performed the same lifting motions in 15 healthy males using a Heel-wedge （with the heel inclined higher than the toes）; the Heel-wedge condition resulted in more flexion of the knee and a smaller trunk tilt forward than in the flat floor condition. This result suggests that the Heel-wedge approach may be more likely to lead to the recommended lifting motion.