Kneeling, Knee Kickers and Kneepads: A Study of Ergonomic Exposures and Interventions for Floor Coverers

• Main Author: Jing, XiaoLu
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2013
• Subjects: Biomechanics; Occupational health; Occupational safety; Public health
• ISBN: 130315594X; 9781303155949

This dissertation discussed ergonomic exposures and interventions for floor coverers. Study I evaluated whole body ergonomic exposures for floor coverers by specific tasks, and collected other work-related factors using an observational exposure assessment approach. In this study, kneeling was observed 56.0% of the time. Floor coverers spent more time kneeling than in neutral leg postures. VCT and hardwood floor tasks had a relatively high combination of kneeling and MMH (26% for VCT and 20% for hardwood floor). Study II was a biomechanical evaluation of the carpet knee kicker. A typical kicking action was divided by four phase: windup (I), kick (II), recoil (III), and release and adjustment (IV) in order to discuss the time consequence among muscle activities, body postures and impact forces. A typical impact contact only lasts about 0.08 seconds, and it takes less than 0.04 second for the impact force to reach the peak from the baseline. The peak impact force, minimum hip and knee extension appears almost simultaneously. On average, subjects exerted an impact force 1.32 times as much as their body weight. Study III compared the muscle activities and segment motions between the kicker and the air stretcher for the kicking/stretching and the in-between phase. For both the kicking/stretching phase, there were significant differences for the leg muscles (BF and RF) with a higher %MVC from the kicker. However, for the in-between phase, there were no significant differences for the leg muscles (BF and RF), except BF at 90th level. These finding indicated that the new tool did not create more leg muscle strain at the in-between phase while dramatically decreasing leg muscle activities for the kicking/stretching phase. For postural data, the stretcher significantly decreased range of motion (90th -10th) for both knee and hip extensions for both phases, and it eliminated several extreme extensions (10th and 90th). The new tool changed users' body postures: workers tended to keep higher knee extension and lower hip extensions for both phases. Based on the above results, the air stretcher significantly decreased major muscle activities during the kicking/stretching phase; it also decreased range of motion for the knee and hip. Study IV compared contact areas, mean and peak pressures in kneeling while wearing an advanced (Pro Knee) kneepad, a regular kneepad, and no kneepad. Both kneepads increased the contact area, and the advanced kneepad had a much larger contact area than the regular one. Sitting on heels led to less contact area than kneeling, and more trunk flexion resulted in more contact area. The bare knee was associated with much higher mean and peak pressure than either kneepad. Leg posture had a significant impact on contact area and mean pressure, but no impact on peak pressure. Trunk posture only had an impact on contact area. Arm posture had no significant impact on any of these three dependent variables. Work-related factors (Good Pressure Distribution, Improving Work Performance) had high importance scores. Some usability factors, such as Well Attached to the Knee, Durability, Easy to Get on and Take off, Not Getting Sweaty, also received importance scores greater than three. Workers were less interested in factors such as Good Customer Service, Low Cost, Light Weight and Good Aesthetic Factors. The advanced kneepad was rated higher on all factors with an importance score over three over the regular pad. The regular kneepads gained the advantage for factors that had importance scores less than three.