The purpose of this study was to use EMG data of the erector spinae muscles synchronized with three-dimensional video techniques to determine the body's responses to asymmetric lifting under weight belt conditions. The subjects performed static maximum voluntary exertions and dynamic lifts from 0° and 45° from the midline of the body. Three weight belt conditions were used. EMG data revealed significant differences in EMG variables with belt conditions. Weight belt use decreased burst area, peak voltage, and maximum frequency. Kinematic data indicated a significant difference in the left knee and left and right elbow range of motion when the type of lift, symmetric or asymmetric, was considered. Lifting technique also produced a significant effect on the maximum and minimum velocity of the center of mass. The results of the study indicate that weight belt use is an effective means of reducing spinal compression and thus may be helpful in preventing low back injury. / School of Physical Education

Low velocity impacts to the back are known to cause severe injury to crucial components such as the spine and kidneys. Researchers at Natick Soldier Center want to develop a solution that incorporates protection against low velocity impacts with the ballistic body armor (vest and plate) that is used today. The current ballistic body armor was developed to provide ballistic protection. Ballistic protection is designed to stop the penetration of bullets at velocities exceeding 300 m/s. Techniques to provide low velocity impact protection include reducing transmitted force by elongating collision time. In order to develop back protection for the soldier against low velocity impacts the performance of the ballistic body armor and impact protecting foams was evaluated. Low velocity impact tests were performed based on European standards for back protectors for horse riders (EN 13158) and motorcyclists (EN 1621-2). Performance requirements outlined by the standards and published literature established peak forces of 4 kN and 9 kN transmitted through materials under impact as minimum levels of safety before significant injury occurs. Experiments were conducted at an energy level of 4 J to compare the performance of different materials. Energy levels were then increased until maximum acceptable force transmissions were reached. At 4 J the ballistic materials showed peak transmitted forces between 11.0-16.2 kN. This indicated that the ballistic materials were not an adequate method to provide sufficient back protection. The addition of polyurethane foams to ballistic materials reduced peak force values by a factor of 15. Energy levels of 25 J and 40 J were reached with peak forces of 3.5 kN and 6.6 kN. This research provided a basis for the future development of protective equipment that provides both ballistic and low velocity impact protection.