Eleven healthy male volunteer soldiers (mean [SD] age 24-0 12-81 years, stature 174.1 [5.2] cm, body weight 73.2 (10.81 kg, body fat 14-2 [S-01 % and maximal oxygen uptake 4.1 [0.4] 1 min'l) walked at 4-8 km h' l on a motor driven treadmill for 5 min at each of three gradients (0, 2.5 and 5%) whilst carrying a two-part 26 kg load either on each shoulder or strapped to a backpack frame. The load was made up of two cylinders, one weighing 18.4 kg and the other weighing 7-6kg. For all treadmill gradients the mean (SD) backpacking heart rates and oxygen uptakes (0% gradient, 122 (101 beats min'', 1.5 1 [O-111 1 min-I; 2.5% gradient, 135 [ I 0] beats min", 1.8 1 [0.13] 1 min-I; 5% gradient, 155 [7] beats mine[, 2-21 [O-1 1) 1 mine[) were significantly (pCO.00 I ) lower than for shoulder load carriage (0% gradient, 130 [9] beats min-I, 1.70 [O-121 1 min-I, 2.5% gradient, 147 [8] beats min-I; 2.01 [Om 101 1 min-I; 5% gradient 164 (91 beats minet, 2:39 [O. 1 11 1 min'').The relative oxygen cost of backpacking was 4.3-4.7% V 0 2 max lower than for shoulder load carriage. It is concluded that the metabolic cost of backpacking an asymmetric two pan 26 kg load was significantly less than for shoulder load camage when walking at 4.8kmh-I on a treadmill over gradients of 0-5%. It is likely that under field conditions for this particular load soldiers may find the shoulder load carriage method acceptable for approximately 1-1-5 h but may tolerate the backpacking method for longer periods of time.