Symptoms during load carrying: effects of mass and load distribution during a 20-km road march.

Soldiers must often carry heavy loads which can lead to symptoms of body soreness, aches, pains, and tiredness. This study assessed symptoms when soldiers carried loads in the standard U.S. Army ALICE pack (a single backpack) and in a prototype Double Pack (a two-pack system designed to alleviate symptoms by evenly distributing the load between a backpack and a frontpack). Each of 15 male soldiers completed a 20-km (12.4 mi) road march while carrying either 34, 48, or 61 kg (75, 105, or 135 lb) and while wearing either the ALICE pack or the Double Pack. Symptoms included feeling alert, good, and wide awake. Postmarch symptoms included tiredness, muscle tightness, and soreness of the legs, feet, back, and shoulders. Analyses of eight symptom factors showed that (a) as load increased, fatigue and muscle discomfort intensified, and alertness and feelings of well-being diminished and (b) distress and heat-illness indices were most intense at 61 kg with the Double Pack.