PRESSURE EXERTED BY PACK STRAPS AS RELATED TO LOAD CARRIED AND CHEST DIMENSIONS
Rept. no. 4 on Physiology of Load Carrying
SPRINGFIELD COLL MA
Pagination or Media Count:
A special pressure meter was devised to measure strap pressure. It consists of a sphygmomanometer in which the rubber cuff has been replaced by a rubber tube. Strap pressure was tested on 39 male subjects who carried high or low packs weighing from 20 to 70 lb while standing still on horizontal, downgrade, or up-grade planes, or waking on the same planes. A mathematical relationship between strap pressure and pack weight was established, and formulas were derived for determining strap pressure in pounds while standing or walking, when pack weight was known. In standing, the strap pressure is greater at the top than at the front of the shoulders. For a 40-lb pack, these pressures are 6 and 4.4 lb, and for a 70-pack, they are 10.5 and 7.4 lb, respectively. During walking, the pressure increase. For a 40-lb pack it becomes 9.6 and 6.3 lb, and for a 70-lb pack, 15.5 and 10.0 lb. The relation between strap pressure and the chest size was studied on 49 men. It was found that the larger the chest, the greater the pressure on the shoulder front and the smaller the pressure on the shoulder top. The pressure meter was a reliable instrument with an objectivity coefficient of 0.93 during measurements when the subject is standing, and 0.96 when the subject is walking, By means of this meter, the probable degree of comfort or discomfort of a newly designed pack may be objectively measured. The meter can be used very easily, will give reliable information, and will save time.
- Anatomy and Physiology