Twelve healthy, male Army recruits performed three, 40-min treadmill marche
s at 6 km/h, under three load carriage conditions: 0%-body weight (BW) back
pack load, 15%-BW load and 30%-BW load. Kinematic and kinetic data were obt
ained, immediately before and after each treadmill march, for computing ank
le, knee and hip joint rotations and moments. Metabolic data (oxygen uptake
((V) over dot O-2), expired ventilation ((V over dot) E), respiratory exch
ange ratio (RER)), heart rate (HR) and ratings of perceived exertion (RPE)
were collected continuously during marching. Significant differences (p les
s than or equal to 0.05) were observed between each load for (V over dot) O
-2, HR and (V) over dot E)throughout the marches. At 40 min, relative energ
y costs for 0%-BW, 15%-BW and 30%-BW loads were 30, 36 and 41% ((V over dot
) O(2)max, respectively. RPE responses during marching significantly differ
ed for only the 30%-BW load and were greater than responses at 0%-BW and 15
%-BW loads. During load carriage trials prior to treadmill marches (pre-mar
ch), peaks in internal, hip extension, knee extension and ankle plantar fle
xion moments increased with increasing backpack load. Relative to 0%-BW loa
d, percentage increases in knee moments, due to 15%-BW and 30%-BW loads, pr
e-march, were substantially larger than the percentage increases for hip ex
tension and plantar flexion moments, pre-march. Pre-march and post-march pe
aks in hip extension and ankle plantar flexion moments were similar with al
l loads, while notable pre-march to post-march declines were observed for k
nee extension moment peaks, at 15%-BW and 30%-BW load. Pre-march joint load
ing data suggests that the knee may be effecting substantial compensations
during backpack loaded marching, perhaps to attenuate shock or reduce load
elsewhere. Post-march kinetic data (particularly at 15%-BW and 30%-BW load)
, however, indicates that such knee mechanics were not sustained and sugges
ts that excessive knee extensor fatigue may occur prior to march end, even
though overall metabolic responses, at 15%-BW and 30%-BW load, remained wit
hin generally recommended limits to prevent fatigue during prolonged work.