The Navy SEAL Physical Fitness Guide 179
Hydration Status
Appropriate water/fluid discipline must be observed at all times during load-
bearing. Exercise without a load is severely compromised when dehydration occurs, and
when exercise is coupled to load-bearing, dehydration potentially becomes an even
greater threat. This is true regardless of the environmental conditions. The Navy SEAL
Nutrition Guide provides information on optimal fluid ingestion, but in brief, you should
ingest at least one to two cups of fluid every 30 minutes during a hump.
Fluid requirements are higher during
exercise with load-bearing than during
exercise without load-bearing.
Environmental Stress
" Hot and dry or hot and humid environments will increase the heat strain
of individuals during load-bearing. Thermal heat load will be increased due to
body heat production from load-bearing activities, and from the heat load
from the sun and other heat sources in the environment. ALICE packs and
double packs can restrict the body’s ability to dissipate heat. Load-bearing
vests with a nylon mesh body will trap less heat than backpack designs." Cold environments increase the energy cost of walking because the clothing
worn is usually heavy and cumbersome. This can result in overheating and
sweating, especially on the back where the load is carried. Hypothermia
(drop in body temperature below 95 ̊C) can also occur rapidly in cold envi-
ronments if the inner layers of clothing are wet when you stop exercising." Moderate to high altitudes decrease exercise capacity since the available
oxygen in blood decreases as altitude increases due to lower barometric pres-
sure." Sandy terrain significantly increases energy expenditure up to 80% or
greater as compared to walking on a firm surface. The energy demand
increases with the difficulty of the terrain.Sleep Loss