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CLOTHING TEST METHODS slight and more difficult to evaluate and so may be disregarded. It is believed by some explorers that full and complete acclimation requires as long as six or nine months. In experimental subjects, retrogression or even intolerance to the cold may develop after several months of repeated daily exposure. Whether this is a pure effect of exposure to the cold or intolerance to being an experimental subject, the phenomenon should be recognized when it occurs. Once a subject is acclimated he will maintain effective acclimation with no more than two or three exposures per week, three or four hours each. Quartering and Messing Subjects should be housed and messed together in barracks and mess hall adjoining the laboratory if possible, Unless dietary studies are a primary ob- ject of the test, a constant dietary intake need not be provided. The twenty- four hours prior to an experiment are important, especially with regard to alco- holic consumption and adequate rest. Pretesting Conditioning Uncontrolled vasodilation and sweating or vasoconstriction and chilling should be avoided during the sixty-minute period prior to each experiment. The preferred dressing-room temperature for cold-room work is 60°P. A controlled degree of asodilation is permissable, such as may be produced by a fixed amount of work or by diathermy. It should be remembered, however, that the effects of a single exposure to severe heat may last several days and partial acclimation to heat may complicate cold-room experiments. At one laboratory in this country .studies on acclimation to the cold are conducted only in the summer and acclimation to the heat only In the winter. This is desirable but it should not preclude cold-room testing in the winter or hot- room testing in the summer. Time of Day Data on a comparative study of similar items should be collected at the same time of each experimental day. The tolerance times tend to be larger and the skin temperatures higher in the afternoon than in the morning. If a series of experiments are planned, the morning series should be considered independently of the afternoon series. Furthermore, there is some evidence from the Climatic Research Laboratory studies which indicates that evening conditions are yet dif- ferent from afternoon and morning. Regular meals should be provided when daytime gear is tested during morn- ing and afternoon exposures. If sleeping gear is tested during the day there should be no intake of food during the exposure in order to more closely simulate conditions in the field. Stabilization Period Some laboratories provide a stabilization period for subjects In the cold room before the collection of data. At the Fatigue Laboratory, this consists of a short walk at a standard rate in order to produce vasodilation. Other labora- tories do not precede their experiments by such a procedure. If a stabilization period provides sufficiently strenuous exercise to produce sweating this should be taken into account, since profuse sweating into thick garments may reduce tolerance times appreciably. Until it has been demonstrated that a stabilization period is necessary, it should be optional with each laboratory.
STANDARDIZATION OF SUBJECTS 43 Reaction to Gold This should be determined for each subject, since the variation from sub- ject to subject in an acclimated group of individuals is considerable. At the Climatic Research Laboratory the subjects are classified as Resistant, Average, and Susceptible to the cold. The reaction of each subject may usually be deter- mined within a few days after acclimation has been effective. A resistant or susceptible reaction to the cold may apply only to a particular portion of the body. Thus an average reactor in sleeping gear may be susceptible when footgear is tested. The classes of items that may be differ- entiated in regard to reaction produced are footgear, handgear, clothing and sleeping gear. At the Climatic Research Laboratory it has not been observed that a resistant subject in one gear is a susceptible subject for another type of gear. The only variation that has been observed is up or down one grade and not two grades, such as resistant to average or average to susceptible. Furthermore, in any type of gear a subject may change from being an average subject one month to a susceptible subject the next month. Most subjects, however, maintain the grade of reaction for the eight or ten weeks period of experimental exposure. It is recommended that the experimental data be surveyed periodically and the sub- jects placed in their proper category. Clothing Worn A subject should be very well clothed, even overdressed, in all parts of the body that are not being tested. Since no clothing combination provides com- plete protection at rest for indefinite periods of the time below zero without supplementary heat, it is impossible to overdress a subject with functionally use- ful gear at these temperatures. In order that adequacy may be approached as nearly as possible, it may be desirable to provide for such items as a face mask in a footgear study at subzero temperatures. In testing handgear and footgear it is important that the clothed body be exposed to the same ambient temperature, in order to produce generalized vaso- constriction similar to that encountered under actual conditions in the field. If only a hand or foot is expose;! to the cold, the remainder of the body meanwhile being in a warm environment, the absence of generalized vasoconstriction and the failure to lose stored body heat, will alter the final result materially. Activity The amount and duration of activity during exposure should.be stated. If possible, exercise should be graded and carried out on a treadmill with recording of oxygen consumption in a few instances to verify the level of activity. If a treadmill is available, walking with a pack should be at the rate of 3.5 miles per hour, walking fifty minutes and resting ten minutes out of the hour. If a pack is carried, it should be standardized at 40 pounds and the rate should be 3.0 miles per hour. Since reproducible data are obtained best in the resting state, this will probably be preferred for most cold-room studies. Rest should be as absolute as possible since any movement of the body or movement locally of fingers and toes will influence tolerance time. Fit of the Gear Unless specifically requested to the contrary, gear should be selected for each subject that would provide a suitable fit in the field. In the testing of handgear and footgear it is especially important that constriction be avoided since this will shorten tolerance time markedly. Conversely, if an unnecessarily
44 CLOTHING TEST METHODS loose-fitting gear is worn, it should be so stated, since such gear would not usually be issued in the field. Adequacy The term adequacy, when used in the description of gear, should be clear- ly defined. It should be defined as to whether it is adequate functionally and useful for the mission for which it was devised. Secondly, the amount of activi- ty should be clearly stated. Finally, tolerance time with the degree of exercise permitted should be noted. ADDENDA This was submitted to Captain Steven M. Horvath, Armored Medical Research Laboratory, who differed in two paragraphs as follows: Acclimation There is no real evidence that the phenomena of acclimatization (in terms of the acclimatization observed for hot environments) exists for cold environments. If such a phenomenon exists, its magnitude must be very minute since no definite physiological effects have so far been accurately delineated. Many people believe that what has been glibly called acclimatization is really nothing more than be- ⢠coming used to handling oneself and ones clothing and equipment efficiently in the cold. Regardless of whether or not there is acclimatization, subject* for cold-weather testing must have had recent experience with cold. Activity If a treadmill is available, walking with a pack (20 pounds for Armored personnel and 40 pounds for others) should be at the accepted Army rate of 2.5 miles per hour, walking fifty minutes and resting ten minutes out of the hour. If a pack is not carried, it should be standardized at J.O miles per hour and a five per cent grade.
STANDARDIZATION OF CLOTHES AND GEAR John H. Talbott It is believed unnecessary by some laboratories to condition items before use. Other laboratories believe it is desirable. If clothes are conditioned before use it would be desirable to have them kept overnight in an atmosphere of 50 per cent relative humidity at approximately room temperature. If items are worn daily in the cold room and stowed away in a locker with little or no ventilation at night, essentially the same effect will result as if they were left in a conditioned room at the above humidity and tem- perature. When garments are used for the first time, either new or unused for some weeks, the tolerance time may be longer until such time as the garments take up considerable moisture from the body. The precooling of garments for the cold room is not recommended since it will shorten the tolerance time considerably. There is little need to precool sleeping bags before use. Except in a grossly inadequate sleeping bag, most of the body heat that is expended in warming up the bag immediately after entering it, is not lost. It would have been dis- sipated eventually in a 6-hour exposure period without reducing significantly the tolerance time.
