To study the effects of the strap pressure of a 9kg rucksack on physiological and psychological responses by using two different strap widths, 6cm width and 2cm width, eight female subjects participated in the present experiment. Strap pressures at the shoulder were 30±3.5mmHg in 6cm width and 70±5.4mmHg in 2cm width. Finger blood flow (FBF) was significantly lower in 2cm width than that in 6cm width at 60 min. Heart rate (HR) increased and was kept at a constant level in 6cm width for 60 min. However, HR increased after 40 min in 2cm width, which was probably linked with decreased FBF. It is suggested that the increased HR and falling FBF were induced by varoreflex in 2cm width strap pressure.
　In the forearm muscle tissue, oxygen saturation (StO₂) and oxygenated hemoglobin contents (HbO) were lower in 2cm width than 6cm width, while deoxygenated hemoglobin contents (HbD) were higher in 2cm width than in 6cm width. These results suggest that muscle blood flow were greatly diminished by a narrower strap than by a wider strap. Subjects voted harder pressure and more unpleasant sensations in 2cm width compared with 6cm width throughout the experiment.
　In addition, we examined the manual performance of six operations after carrying the rucksack for 60 min. Finger torque exercise and maximum torque strength were significantly lower in 2cm width than in no pressure control. Endurance time of finger ergometer was significantly shorter in 2cm width than that in 6cm width and no pressure control. It was suggested that comparatively poorer endurance performance in narrow strap width was mainly induced by decreased muscle blood flow.
　These results showed that there was no significant difference between either strap width on physiological responses after a short period of strap pressure. However, there were significant differences after a longer period.

DESCENTE SPORTS SCIENCE Vol.20/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE