and in large heterogmore than one type of injury.). The proportion of soldiers injured decreased enous military units that contain as age increased. Slower 2-mile run times and fewer sit-ups were associated many occupational groups. '`-` Howwith a higher incidence of musculoskeletal injuries. This study documents ever, reliable information on injury the injury incidence in infantryi soldiers and identifies younger age and low incidence in specific military occupaphYsical fitness as potential risk.factors for these injuries.tions (e.g., infantry. artillery. or armor soldiers) is still lacking. It has been proposed that, in both civilian and military populations, the This document has been approved likelihood of activity-related injuries for public • elease and sale; its may be modified by a number of vari-

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.

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