No abstract

Fifteen male soldiers performed six maximal-effort, 20-km road marchers. They carried load masses of 34, 48, and 61 kg, using a standard military backpack with frame or an experimental doublepack. March times decreased as mass increased and were faster with the standard pack than with the double-pack. The doublepack resulted in less low back discomfort and a lower incidence of blisters at the highest load, but also resulted in more discomfort in the neck and hips. Neither load mass nor pack type affected soldiers' marksmanship ability, grenade throw accuracy, or cognitive ability. The maximal-effort march itself affected the marksmanship tasks by increasing the post-march vertical shot group dispersion. The concept of distributing the load mass more evenly around the center of mass of the body has both positive and negative aspects and warrants further investigation.

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect to this collection of information, including suggestions for reducing the burden to, Department of Defense, Washington Headquarters Services, Directorate for Information 14. ABSTRACT Data from four studies of standard and prototype load-carriage equipment were analyzed to determine the effects of the weight borne by male and female load earners on time to traverse a 3.2-km course at maximal speed and on energy expenditure and kinetic and kinematic variables during externally paced walking at 4.8 km-hr " 1 . The equipment configurations included fighting, approach, and sustainment :oads, with masses varying from 12 kg to 50 kg. It was found that course completion times and energy expenditure were directly related to the weight earned. Kinetic variables, including ground and joint reaction forces, generally evidenced substantial linear relationships with :he weight earned. Increases in maximum ankle, knee and hip joint reaction forces approached 1 N for each 1 N increase in the weight. The effects of weight earned on the kinematic variables were more complex. They included evidence of adaptations in walking gait that are likely to aid the load earner in maintaining stability and in absorbing the increased forces associated with increased load on the body.

This study investigated the effects on metabolic cost and gait biomechanics of using a prototype lower-body exoskeleton (EXO) to carry loads. Nine US Army participants walked at 1.34 m/s on a 0% grade for 8 min carrying military loads of 20 kg, 40 kg and 55 kg with and without the EXO. Mean oxygen consumption (VO(2)) scaled to body mass and scaled to total mass were significantly higher, by 60% and 41% respectively, when the EXO was worn, compared with the control condition. Mean VO(2) and mean VO(2) scaled to body mass significantly increased with load. The kinematic and kinetic data revealed significant differences between EXO and control conditions, such as walking with a more flexed posture and braking with higher ground reaction force at heel strike when wearing the EXO. Study findings demonstrate that the EXO increased users' metabolic cost while carrying various loads and altered their gait biomechanics compared with conventional load carriage. STATEMENT OF RELEVANCE: An EXO designed to assist in load bearing was found to raise energy expenditure substantially when tested by soldiers carrying military loads. EXO weight, weight distribution and design elements that altered users' walking biomechanics contributed to the high energy cost. To realise the potential of EXOs, focus on the user must accompany engineering advances.

This study was conducted to determine the effects on manual dexterity of the thickness of handcovering. Twelve men were timed as they performed five dexterity tests while barehanded and while wearing each of three thicknesses of chemical protective gloves, 0.18 mm, 0.36 mm, and 0.64 mm. The subjects participated in 14 sessions held on consecutive weekdays. Analysis of the data from six sessions spanning the test period yielded significant main effects (p < 0.001) of handwear and of session on all dexterity tests. Mean times were best with bare hands and poorest with the 0.64 mm gloves. Performance with the gloves improved over sessions to the extent that the results with gloves approached or surpassed performance levels achieved with the bare hands during the early sessions. Regression analyses carried out on the data from the last three sessions revealed a linear increase in times to test completion as a function of increases in thickness of the handcovering. The occurrence of damage to the gloves, in the form of punctures and tears, was inversely related to thickness. The findings suggest that selection of the thinnest glove material compatible with protection from the chemical environment and practice working with the handwear will result in relatively efficient manual performance.