The effects of sloped ground on the hip, knee, and ankle joint kinetics and kinematics during manual lifting tasks.

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Title: The effects of sloped ground on the hip, knee, and ankle joint kinetics and kinematics during manual lifting tasks.
Author: Shin, Gwanseob
Advisors: Dr. Eric Klang, Committee Member
Dr. Carolyn Sommerich, Committee Member
Dr. Gary A. Mirka, Committee Chair
Abstract: The biomechanical effects of sloped ground on hip, knee, and ankle joint moments and lifting posture during sagittally symmetric manual lifting were investigated using a two-dimensional five-segment dynamic biomechanical model. Subjects' motions were traced and recorded at 60Hz by Flock of Birds magnetic tracking system as they lifted a 10 kg cubic box on five sloped grounds; two declined slopes (-20°, -10°), two inclined slopes (+20°, +10°), and flat ground (0°), using three lifting techniques; back lift, freestyle lift, and leg lift. Fifteen trials were tested and each trial involved repetitive lifting (6 to 9 lifts per trial) for 50 seconds. The kinetic and kinematic effects were examined by computing the peak net reactive moments at the hip, knee, and ankle joints, and measuring peak segment flexion angles of the trunk, thigh, and leg (shank). Results indicated that the peak joint moments and peak segment angles were significantly affected by slope angle and lifting technique (α = 0.05). The inclined slope angles (10° and 20°) caused up to 6.8 % and 14.3 % larger peak hip moments than flat ground during the freestyle and leg lifts, respectively. The lowest peak hip moment (236.48 Nm) was observed during the leg lift on flat ground and the largest peak hip moment (302.62 Nm) occurred during the back lifts on flat ground. The components contribution analyses showed that the two static components (vertical reaction static force on the shoulder joint and the trunk mass) were main contributors to the responses of peak hip moment to changes in slope angle. The leg lift technique produced significantly less peak joint moments than other lifting techniques regardless of slope angle. The mean peak hip moment was 16.0 % and 10.5 % less in the leg lift technique (251.0 Nm) than in the back (298.8 Nm) and freestyle lift (280.4 Nm) respectively. Specifically, trunk angular acceleration acted as a major contributor to the significant difference in peak hip moments between the back lift and the leg lift. The trunk angular acceleration, peak flexion angles of the trunk, thigh, and shank separated the leg lift from the back lift.
Date: 2002-08-21
Degree: MS
Discipline: Industrial Engineering

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