Pressure on the knee while performing a lateral lift from kneeling postures.
Mayton-AG; Pollard-JP; Porter-WL; Moore-SM
Proceedings of the 34th Annual Meeting of the American Society of Biomechanics, August 18 - 21, 2010, Providence, Rhode Island. Newark, DE: The American Society of Biomechanics, 2010 Aug; :1-2
Estimated mean pressure versus posture is shown in Figure 1 for the static trials that were collected as part of the larger study and the three lifting stages. Similar results were found for the Near 90 and One Knee postures for all trials, as expected considering postural similarities. Estimated pressures increased in all postures when performing the lifting trial compared to the static trial. Drastic increases were noted in the Near Full posture during the lifting task. Highest mean pressures were seen at the BPU stage where estimated pressure exceeded 20 psi, which was more than four times the pressures estimated for the other postures. One reason for the notable differences in estimated mean pressure is smaller mean contact area. While forces for the Near Full posture were within 0.8 to 1.4 times the measured mean forces of the Near 90 and One Knee postures, the mean contact areas were 1.8 to 4.7 times lower for the Near Full posture. This is likely due to the contact of the tibial tubercle with the force plate when kneeling in full flexion. When normalized to the static posture, estimated mean pressures for the Near Full posture exceeded those for the static trials by factors of 11, 8, and 5 for BPU, BAF, and BPD, respectively. An ANOVA showed posture was statistically significant (p=0.003) for normalized mean pressure. Differences in subject anthropometry and tubercle prominence may explain the wide variation in contact area, and thereby the variation in knee pressure for the Near Full posture. Figure 1 also suggests the Near 90 and One Knee postures are preferred for lateral lifting. The mean pressure magnitudes during each stage of lift for these postures are similar to those during static kneeling. In considering a postural rotation strategy, these findings suggest that, in moving supplies with a lateral lift technique, workers should limit using the Near Full posture and instead use Near 90 or One Knee whenever possible. Observations have shown low-seam coal miners to most often use the Near Full posture. These miners routinely wear kneepads, which have been shown to aide in minimizing peak stresses on the knee while the mean pressure is not greatly affected. Some limitations of this study included the effect on contact area estimates due to the size of the sensing units and associated gaps of the sensor and the inability to report peak pressures.
Musculoskeletal-system; Ergonomics; Manual-lifting; Knee-injuries; Knee-protection; Injury-prevention; Mining-industry; Underground-mining; Underground-miners; Mine-workers; Coal-miners; Coal-mining
Proceedings of the 34th Annual Meeting of the American Society of Biomechanics, August 18 - 21, 2010, Providence, Rhode Island