and the risk of heat injury and disability is high. A period of acclimatization is necessary
regardless of the individual's physical condition, although the better the physical
condition, the quicker acclimatization is completed.
b. Acclimatization to heat begins with the first exposure and is about 80%
developed by the end of the second week. Individuals who are unusually susceptible to
heat will require additional time for acclimatization. Full acclimatization (the ability to
perform a maximum amount of strenuous work in the heat) is attained most quickly by
graded, progressively increasing work in the heat. Resting for 3 or 4 days in the heat,
with activity limited to that required for existence, results in definite but only partial
acclimatization. Physical work must be accomplished but should be limited to brief
periods. A day or two of intervening cool weather will not interfere significantly with
c. A schedule should be established which provides for alternating work and rest
periods. Although advantage should be taken of the cooler hours in accomplishing a
portion of the work, the schedule should include gradually increasing exposure during
the hotter parts of the day rather than complete exclusion of work at that time. The work
period should be divided so that a man works and rests in alternating periods. When
necessary for the accomplishment of a given task, two details can be arranged to work
d. Adequate water must be provided at all times.
e. Once acclimatized, the soldier will retain his adaptation for about 2 weeks
after leaving the hot environment. But if he is not exposed to high temperatures
thereafter, the acclimatization will then decrease at a variable rate, the major portion
usually being lost within one month.
f. Acclimatization to a hot, dry (desert) environment increases markedly the
ability of men to work in hot, moist (jungle) environment; however, for proper
acclimatization to the latter, residence with regulated physical activity is required. While
carefully and fully developed acclimatization increases resistance, it does not confer
complete protection against ill effects of heat.
g. Under conditions of heat stress, meals should be cool rather than hot. The
heaviest meal should be served in the evening rather than at noon. An hour of rest
following the noon meal is beneficial.
4-18. WORK SCHEDULES
Work schedules must be tailored to fit the climate, the physical condition of
personnel, and the military situation. Close supervision by medical officers, responsible
commanders, and experienced paramedical personnel is essential in achieving
maximum work output with minimum hazard. Certain general principles must be