The average sustainable rate of energy expenditure in men working hard for prolonged periods of time .... drive. These are due to the changes in metabolic regulation that reduce energy ..... Ranger students transported to a lab in Pensacola.
Fact Sheet 5 (Supplement)
Biomedical Studies of U.S. Army Ranger Training
“Rangers Lead the Way!”
U.S. Army Medical Research and Materiel Command Military Operational Medicine Research Program
INTRODUCTION This booklet expands upon the information in a Military Operational Medicine Research Fact Sheet describing biomedical studies on U.S. Army Ranger training. Most of the findings have been published in technical reports and scientific journals. These scientific publications are an important part of documenting research, but are usually not useful summaries for commanders, policy makers, materiel developers, or the soldiers who participated in the studies. This booklet is intended to deliver findings from military biomedical research back to those who may benefit from the information. This research was conducted primarily by scientists from the U.S. Army Research Institute of Environmental Medicine (USARIEM) but included some joint projects with the Walter Reed Army Institute of Research (WRAIR) and the U.S. Department of Agriculture. Earlier projects involving Ranger training were conducted by the Nutrition & Biochemistry Division at the Letterman Army Institute of Research. Comments and questions are welcomed: 301/ 6197301.
TABLE OF CONTENTS Energy Balance and Sleep Duration Weight Loss Body Composition Changes Physical Performance Changes Biochemical Changes That Help Regulate Metabolism Sleep Restriction and Mental Status Susceptibility to Infection Susceptibility to Cold Nutritional Adequacy of Rations Recovery from Ranger Training Future Research Reference Publications
1 3 5 7 9 11 13 15 17 19 21 23 1
ENERGY BALANCE AND SLEEP DURATION The Ranger course has evolved through trial and error to provide a high level of stress that is still tolerable to the most dedicated students. Food and sleep restriction are deliberate stressors that are used to test and train small unit leaders in managing personal adversity. Other stressors include prolonged work, environmental heat and cold, and hardships associated with living in the environment (being wet from stream crossing or rain, chigger bites, etc.). In 1991, an epidemic of pneumonia disrupted one of the courses and military medical researchers were asked to quantify the stress of Ranger training and determine the associated medical risks. One of the questions posed to the medical researchers was to determine if there was a scientific basis for providing supplements such as a vitamin pill or amino acid to reduce medical risks without significantly reducing the challenging nature of the training. In 1992, a second study of summer Ranger training tested the impact of a modest increase in calories (+ 400 kcal per day). At the time of these studies, students were being fed one MRE per day for half of the course. This produced semistarvation in four repeated cycles of adequate feeding followed by restricted feeding, with a progressive loss of body weight through the course. Students were also scheduled for limited organized sleep. The actual sleep measured in these studies averaged 3.6 hours per day over the entire course. Energy expenditure was highest at the start of the course during the Ranger Assessment Phase (RAP) testing and during the mountain phase; the mountain phase remained the highest period of energy expenditure even when the sequence of training phases was changed in 1992. Since these studies, the course has been returned to three phases of training with elimination of the desert phase (for cost saving reasons).
Deliberate stressors in Ranger training include inadequate sleep and restricted food intake. Medical researchers were asked to determine how to make training safer without making it less challenging. Understanding the limits of human health and performance in the face of these stressors is important for all combat forces.
2
ENERGY BALANCE AND SLEEP DURATION
CAMP ROGERS
CAMP DARBY
ENERGY INTAKE AND EXPENDITURE (kcal/day)
(Ft. Benning)
CAMP MERRILL
CAMP RUDDER
CAMP McGREGOR
(Mountain Phase)
(Jungle Phase)
(Desert Phase)
Energy Expenditure
1991
Difference Between Energy Intake and Expenditure Is Fueled from Body Tissues
6000 Food Intake
Energy Requirement Exceeded by Food Intake 1 MRE per Day During Patrols
4000 RAP 2000
3.8 hrs.
3.3 hrs.
3.1 hrs.
Average Sleep (3.6 hrs. per 24 hrs.)
4.1 hrs.
0 0
10
20
30
40
50
60
DURATION OF COURSE (Days)
3
WEIGHT LOSS The simplest and most informative overall indicator of nutritional status is body weight. From anecdotal information at the time the studies began, the research team expected to observe a few weight losses as large as 10% of starting body weight. Instead, the 1991 study demonstrated that all but two of 55 students completing the study lost at least 10% of their body weight, with an average loss of 16%, or 27 pounds, from start to finish. These were startling results, even for the cadre at the school. The 1992 study provided a controlled feeding “intervention,” where the only change in the course stressors was to provide additional food, averaging 400 kilocalories per day more than in 1991. This reduced the weight loss to an average of 12% which had significant benefits to protecting against excessive loss of muscle (shown in the next section). The 1995 study of Winter training examined the effect of doubling the energy intake during the restricted periods (2 MRE’s per day). The weight loss averaged 5% of initial body weight and some students actually gained weight during the course. With no change in energy demands of the course, this increased intake would be predicted to result in an average weight loss of about 8 pounds during the course, equal to the 5% change actually observed. The average sustainable rate of energy expenditure in men working hard for prolonged periods of time appears to be about 4,000 kilocalories per day. This is the value actually measured during Ranger training. With this information, food requirements can now be accurately calculated for any level of acceptable weight change during Ranger training. The National Academy of Sciences reviewed the medical research data from Ranger training and recommended that the maximum weight loss should be limited to no more than 1012% of initial body weight. The current policy of feeding 2 MRE’s per day ensures that only a few individuals come close to this safe limit of weight loss (see green distribution curve on the facing page). Energy requirements which are not balanced by food intake are met by body energy stores, reflected in weight loss.
4
WEIGHT LOSS % WEIGHT LOSS (DISTRIBUTION OF INDIVIDUALS)
Number of Soldiers
2 MREs
5%
1 MRE + Food Suppl. (~400 kcal)
12%
Weight Gain
~ 8 lb. Weight Loss Weight Loss
Nearly every student lost at least 10% of their body weight; the most extreme loss was 23% in a lean soldier
1 MRE
16%
Body Energy Stores Energy Intake
Energy Demands
~ 3500 kcal per day
~ 4000 kcal per day
1995 1995
1992
1991
0 +5
0
5 15 10 20 Weight Change (% of Starting Weight)
ACTUAL WEIGHT LOSS MEASURED IN 1991
Number of Soldiers
10
Average weight loss in the 1991 course was 27 lbs.
8
LRP
6 4 2 0 0
10
20 30 Loss in Pounds
40
50
• Weight loss rates are controlled by the energy provided in rations and supplements
• Energy requirements have been measured through the entire course using a method with “doublylabeled” water. After soldiers drank a special traceable form of water, urine samples were collected and analyzed to provide accurate measures of cellular metabolism (calories per day) • Trained soldiers can use up to 10,000 kcal/24 hours for a limited period of time, but a sustainable work rate coupled with starvationinduced efficiency is about 4,000 kcal/d
5
BODY COMPOSITION CHANGES Ranger students are relatively lean when they arrive for training, averaging 15% body fat. Some of this fat can be used to provide energy to the body during periods of restricted food intake but a portion of it is essential fat that cannot be used for energy. Structural fat makes up cell membranes, nerve sheaths, and pads key structures such as the eyeball, the kidneys, and the palms of the hands and soles of the feet. In the 1991 study, many of the students reached this minimum level of fat and were beginning to become more reliant on protein breakdown from muscle and other tissues. These students were measured for body fat using a precise xray measuring device at the start of the course and again at 6 weeks and 8 weeks. Many individuals had reached rock bottom for body fat at 6 weeks, with no additional measurable change at 8 weeks. This means that the difference in energy requirements could only come from protein. This data defined the lower limit of body fat in normal men at around 67 pounds of “essential” fat. The fattest individual starting the course at 26% body fat ended the course with 11% body fat; most men completed the course at 45% body fat and were increasingly reliant on their muscle breakdown for energy. The increased food intake in the 1992 study was enough to shift the students away from this catabolic “edge” of depleted fat energy stores and increased utilization of protein (compare “Changes in Percent Body Fat” figures for 1991 and 1992). Physical body measurements such as circumferences and skinfold thicknesses confirmed the findings of the xray machine. The largest change was in the abdominal region, with men averaging 32 inch waists at the start of the course, losing an average 4 inches by the end of the course. For many of the men, skinfolds reached measurements which reflected only the thickness of doubled skin without any fat layer (approximately 4 millimeters). Energy intake in 1991 was restricted to one meal/day for half the time of the course, leading to excessive weight loss which included large losses of lean tissue for some individuals. Energy stores were used in a ratio of about 2/3 fat and 1/3 lean weight until fat reserves became low, after which lean tissue loss increased.
6
BODY COMPOSITION CHANGES CHANGES IN PERCENT BODY FAT “Essential” Fat
Number of Soldiers
(cell membranes, nerve sheaths, structural fat)
1991
5% 15%
Avg. = 14.6%
Circumference Changes
Ranger Student Being Measured for Body Circumferences
Arm Mass –18%
(6 26%)
–1.1”
Skin Fold Changes
–2.25” –1.25” –1.25”
Biceps –34%
–4”
Triceps –49%
–3” Finish
0 0
AVERAGE CHANGES IN BODY MEASUREMENTS*
~4%
Start
Leg Mass –12%
% Body Fat
A moderate increase in calories provided to the Ranger students in 1992 was enough to ensure individuals did not finish the course with all of their fat reserves depleted “Essential” Fat (cell membranes, nerve sheaths, structural fat)
Upper Back –30%
–3”
Side/ Abdominal –63% *1991 Data
1992 24 lbs
15%
(6 26.1%)
FAT LEAN TISSUE 142 lbs
10 lbs
8 lbs
LEAN TISSUE 136 lbs
LEAN TISSUE 132 lbs
Bone Mineral
Finish 0 0
Avg. = 14.2%
Xray Scanner (“DEXA”) Used for Detailed Body Composition Analysis
Weight
Number of Soldiers
8%
~4%
Start % Body Fat
0
Start 2 Weeks 4 Weeks 6 Weeks 8 Weeks 1991 Data
Students lost most available fat and began to lose lean tissue representing about 1520% of their muscle mass; there was no measurable loss of bone
7
PHYSICAL PERFORMANCE CHANGES Overtraining can be defined as a reduction in physical performance following excessive and repetitive training with inadequate periods of recovery. Patrolling and other prolonged physical demands during the Ranger course have been studied as a possible example of overtraining. However, reductions in physical performance in Ranger students are primarily accounted for by inadequate food intake. A recent USARIEM study conducted with two Norwegian SEALS crossing Greenland from South to North (3,000 km) on foot clearly demonstrates that men who are properly prepared and adequately nourished can sustain prolonged physical exercise day after day without a decline in physical performance. A 1973 Ranger study tested aerobic performance with treadmill running. Maximal aerobic performance was reduced by about 10%. After three days of rest and refeeding at the end of the course, these soldiers still had reduced aerobic performance, possibly indicating muscle changes that had not yet recovered. On the other hand, the measured decrease in performance may not be a meaningful change, because of reduced test performance expected from soldiers who frequently have extensive foot problems by the end of the course. Most Army tasks involve strength and strength endurance (e.g., lifting and carrying). Overall muscular strength was measured with a maximal lift test. In 1991, students averaged 160 pounds for maximal lift, well above the Army average of 130 pounds which is based on thousands of tests in healthy young men. By the end of the third phase, this average lift dropped to 140 pounds and, by the end of the course, the average lift was 130 pounds, equal to performance of the average soldier. Individual declines in performance were partially explained by individual losses of muscle mass. Slightly greater food intake in 1992 (and only slight differences in lean mass loss) did not change the results obtained for maximal lift. A related test, a maximal jump test which estimates explosive power, demonstrated similar change. Grip strength and grip hold endurance were tested at the end of each phase in 1991 and showed no changes. In a famous starvation study conducted in the 1940s to determine how to best rehabilitate returning POWs, grip strength declined by as much as 30% when healthy men had lost twice as much lean mass as Ranger students. Apparently, grasping function is preserved until late in starvation as a vitally important capability for survival, or it may be preserved in Ranger students from continuously carrying weapons at the ready. Semistarvation causes metabolic changes which produce preferential breakdown of fasttwitch muscle (strength) and protect slowtwitch muscle (strength endurance). 8
PHYSICAL PERFORMANCE CHANGES Changes in lift strength reduced Ranger students to strength of average soldier
LIFT STRENGTH
Number of Soldiers
Average Weight Lifted: 130
16 14 12 10 8 6 4 2 0
160 lbs
Increased feeding in 1992 did not prevent the reduction in lift strength Lift capacity, which requires explosive power and involves much more of the total fatfree mass, declined significantly between the beginning and end. Finish 80
100
120
The soldiers who lost the most lean tissue had the largest decrements in lift performance. The vertical jump test provides the same kind of information as the lift test.
Start
140
160
Average Soldier
180
200
Lift Weight (lbs)
GRIP STRENGTH
Aerobic performance (VO 2 max) was measured with treadmill tests in a 1973 study involving 10% body weight loss. There was a 10% reduction in measured aerobic capacity which was not immediately recovered after 3 days of food and sleep.
Ranger Students
Maximum grip strength did not change between beginning and end. Grip endurance holding time was tested at every phase and also did not change.
Percent of Initial Strength
100 95 90 85 80 75 70 65
12 Wks Minnesota Starvation Study
24 Wks
No loss of grip strength of Ranger students
5 10 15 Percent Reduction in Lean Mass
9
BIOCHEMICAL CHANGES THAT HELP REGULATE METABOLISM Ranger students are familiar with certain changes produced by semistarvation, such as increased sensitivity to cold and reduced sex drive. These are due to the changes in metabolic regulation that reduce energy requirements and prolong survival in circumstances of reduced food availability. Several circulating hormones were measured in blood samples collected during the course. Growth hormone levels increased during each period of restricted food intake. This is a normal response to semi starvation and an attempt to correct low blood sugar. Hormones that control metabolic rate, including body heat production, rapidly decrease during restricted food intake. These included thyroid hormones and insulinlike growth factor1 (IGF1), both of which are very sensitive to energy and protein deficits. These two hormones were measurably higher during the 1992 course with the slightly increased food intake. Ranger students also decrease the amount of time spent fidgeting, gaining incredible efficiency with an “economy of motion.” By the end of the course, students truly move with a purpose and otherwise remain stationary, conserving limited energy resources. There is probably a link between these automatic behavioral adaptations and some of the hormonal changes, although these have not been carefully studied. A steroid hormone, aldosterone, increased progressively through the course, possibly accounting for an increase in water retention measured in Ranger students by two different methods—stable isotope dilution and bioelectrical impedance. Starvation produces a well known effect of water retention, including in the legs, and some of the swollen knees observed in students may have been related to this water retention rather than to infections or trauma. Testosterone is the primary male sex hormone and the most important anabolic (“protein building”) steroid hormone in the male. During periods of restricted food intake, this promptly decreased, nearly to the low levels observed in castrated men. Cortisol is also a steroid hormone but it has primarily catabolic (or “protein breakdown”) effects. This hormone increased significantly in the second half of the course as body fat stores began to disappear. These hormonal changes extend survival when food is unavailable. We know only enough to conclude that many of these changes are appropriate adjustments for optimal survival under stressful conditions. Artificial manipulation may result in unintended consequences. For example, in an Army study with rats infected with the same type of pneumonia that has caused problems for Ranger students, thyroid levels decreased. It was thought that administering thyroid hormone to these sick rats might speed their recovery; instead it worsened their illness and increased death rates. The body supplies energy for vital functions during semistarvation by reducing metabolic demands and increasing breakdown of tissue. Dramatic responses of the hormones which regulate these systems were observed in Ranger students.
10
BIOCHEMICAL CHANGES THAT HELP REGULATE METABOLISM OBSERVED CHANGES GROWTH HORMONE Increases blood glucose; anabolic effects
IGF1 Decreases muscle building and maintenance (anabolic effect)
INSULIN Moves glucose into cells; decrease helps to sustain blood glucose
THYROID HORMONES Reduces cellular metabolism, including heat production
Blood Levels
IGF1 Thyroid Days of Training
ALDOSTERONE Retains salt and water
CORTISOL Increases tissue breakdown to meet energy needs (catabolic effect)
Key hormones involved in amino acid uptake (IGF1) and metabolic rate (thyroid hormones) progressively decline with underfeeding
Cortisol Blood Levels
Testosterone Days of Training
TESTOSTERONE Reduces sex drive and decreases anabolic effects on muscle Blood Sampling and Onsite Processing
Balance between anabolic (testosterone) and catabolic (cortisol) action is changed to allow tissue breakdown for energy needs
• Tissue fat and protein are increasingly moved to the blood stream to compensate for inadequate energy intake and declining glucose • Most of these blood hormone concentrations are restored to normal levels with periods of feeding during the course
11
SLEEP RESTRICTION AND MENTAL STATUS Inadequate sleep produces specific brain changes which are reflected in certain types of paper and pencil tests. Army laboratory studies with brain imaging have shown areas of sleep deprived brains that start to shut down with a reduced metabolism. Caffeine and specific drugs may temporarily reverse these changes but there is no long term substitute for sleep in a sleep deprived individual. Sleep duration and quality has been studied in three different Ranger classes (1988, 1991, 1992) using a sophisticated wrist mounted activity monitor (developed by the Army). These studies confirm that the average sleep duration for the course is about 3.43.6 hours/night. This produces cumulative fatigue effects and by the final phase of the course some unplanned sleep, including “microsleeps”, is probably unavoidable for most of the men. Sleep also becomes fragmented which reduces the quality of restorative sleep. Performance steadily declined on most of the tests of mental function through the course. The more difficult tests such as reasoning produced the greatest reduction in speed, with speed usually sacrificed over accuracy by tired soldiers. Based on earlier Ranger course observations, medical researchers have recommended that students be provided a full recovery day to include 8 hours of sleep at least between phases. This has been shown to be completely restorative in other studies and it was suggested that this would improve the retention of new material and the training value of the course. On tests of mental functioning, sleep deprived Ranger students maintained high levels of motivation to perform well, but all students showed substantial impairment. Speed was generally sacrificed to maintain accuracy.
12
SLEEP RESTRICTION AND MENTAL STATUS DECODING • Automatic processing • Time dependent • Progressive decline in performance through the course • 33% decrease in speed Actigraph The word lid rhymes with kid. MEMORY words Bin and Can are capitalized. • Conscious memorization The The girl put the bird on the perch. • Recognition, not recall The words Quote and Price are capitalized. • Not time dependent • 7% decrease in accuracy after first phase
Activity Counts
REASONING • Challenging mental processing • Time dependent • 20% decrease in speed in second half of course; accuracy maintained, signifying high motivation
Periods of Low Activity Scored As Sleep
• Inadequate sleep reduces metabolism in specific parts of the brain • More sleep, adequate feeding, and certain stimulants (e.g., caffeine, nicotine) may reverse some of these changes • Active research in lab and field studies continues
Field and Laboratory Tests of MilitarilyRelevant Performance
YES NO barn bid bird cage can flea garage
TRUE FALSE A leads B B is led by A B is followed by A B is led by A A does not follow B
BA AB BA AB AB
B is not followed by A A does not lead B A follows B A leads B A does not follow B
BA AB BA AB AB
CAMOUFLAGED PATTERN • Complex visual processing • Decreased speed and performance after 2 weeks • 15% decrease in speed and accuracy The Mary Mays Field Test Battery used in 1992
13
SUSCEPTIBILITY TO INFECTION Ranger students encounter more problems with infections than would be normally expected in healthy soldiers. These include soft tissue infections (cellulitis), respiratory infections (including pneumonia), and a variety of gastrointestinal and other problems. This increased susceptibility to infection may be caused by the course stressors. Other factors are also necessarily involved, including increased opportunities for infection (e.g., poor field sanitation, skin abrasions, exposure to harmful microbes in polluted water). The 1991 study included several sophisticated tests of immune function to determine if there was a connection with course stressors that might explain the high infection rates. Three main categories of immune function tests have been conducted in Ranger training. A test with seven different challenges to the body’s normal defense systems (a multiple version of the tuberculosis skin test) showed that the level of stress did not change the ability to “remember” previously learned responses to infectious challenges. A variety of tests using whole blood showed a consistent and large decline in the ability of the body to produce responses that would be required in a normal response to infection. Although this was a dramatic response, the significance to infection susceptibility is unknown; in hospitalized immunocompromised patients, the response is much more profound than observed in Rangers. Some of these abnormal responses improved in the 1992 course, possibly related to the increased food intake. Infection rates were also much lower; in the last phase of training in 1992, 3% of the graduates had an infection, compared to 25% in 1991. Whether the increased food intake contributed to a reduced infection rate cannot be concluded from these studies since they were not conducted sidebyside in time. A more recent study with Ranger students examined the response to a vaccine given during the course when stress levels are high to determine if stressors reduce effectiveness. Some of the test volunteers had antibody responses below the level that is thought to be protective, although a larger sample of cadre and students is needed for this experiment to be conclusive. A new study is considering the benefits of a vaccine that specifically protects against pneumonia infections and this would be given before the course begins. The stress effects of Ranger training appeared most prominently on the ability of the body to resist infection.
14
SUSCEPTIBILITY TO INFECTION
IMMUNOLOGICAL “MEMORY” TEST (Multiple Antigens Test) Mixed results, with increased sensitivity to some antigens (e.g., TB) and decreased sensitivity to others
BLOOD TESTS Tests with immune cells (lymphocytes) and hormones (cytokines) TCell Lymphocyte Response Decreased ability to respond to an infection Hormones that regulate immune function (e.g., Interleukin2 and IL2 receptors) Decreased cellular response to infection
RESPONSE TO VACCINE (Hepatitis A Vaccine) Antibody Response Possibly less protection after vaccination in stressed soldiers
Decreased Resistance to Disease • Cellulitis, especially knees • Other soft tissue infections from abrasions and insect bites • Streptococcal pneumonia and other respiratory infections
• Several tests showed the immune system to be effected by extreme food restriction • Slightly more food reduced these changes and infections decreased • A separate study indicated that some immunizations may not protect some highly stressed individuals. Vaccines may work best if given in advance of high stress periods.
15
SUSCEPTIBILITY TO COLD Ranger students are especially sensitive to cold because of their decreased fat insulation and because of metabolic changes caused by semistarvation. Risk of cold injury, especially hypothermia (“nonfreezing cold injury”) which can be life threatening, increases with water immersion and in Winter Ranger courses. Safe limits for immersion tables were originally developed for the Ranger school based on available data from normally nourished unstressed men. These have been revised based on new data from a series of field and laboratory studies. Improvements in the prediction of safe limits will include adjustments for automated warning systems such as MERCURY. MERCURY combines heat and cold strain predictions with realtime weather data to provide the Ranger cadre with a colorcoded map display of training risk. A 1995 study took Ranger students directly from their last patrol in the course to a Navy laboratory where controlled measurements of responses to cold exposure were made. The men did not have normal responses to the cold challenge. For example, shivering which normally increases body temperature was suppressed compared to normal rested men. More importantly, core temperature decreased faster than expected. After rest and refeeding for 48 hours, the responses to cold were dramatically improved. This experiment clearly defined a difference in cold susceptibility in Ranger students. A series of laboratory studies at the US Army Research Institute of Environmental Medicine have used normal volunteers to test the individual effects of exerciseinduced fatigue, repeated immersion cold exposure and rewarming, and more intensive metabolic and muscle stress challenges to identify specific factors which increase cold injury risk. These systematic studies have isolated factors which improve predictions of risk. Studies in 1997 and 1998 used disposable temperature pills to measure continuously recorded body temperatures in Ranger students during their normal training in the final phase of swamp training. This provided new information about normal temperature rhythms in Ranger students, including the finding that the low point in body temperature that normally occurs in early morning ordinarily reaches lower levels than expected, even in relatively warm environmental conditions. These results demonstrate the need to base individual cold risk predictions on response measures other than body temperature. The Ranger Training Brigade uses immersion exposure limits tables for safe cold weather training guidance in the jungle phase. Recent studies have led to significant enhancements in prediction of cold injury risk for soldiers in high stress environments.
16
SUSCEPTIBILITY TO COLD IMMERSION TIME LIMITS
CORE BODY TEMPERATURES (Averages & Ranges) Knee Deep Water
Waist Deep Water
Whole Exposure
< 39°C
Stay Out
Stay Out
Stay Out
Stay Out
40 – 44°C
1 Hour
Stay Out
Stay Out
Stay Out
45 – 49°C
4 Hours If Raining, 2 Hours
3 Hours If Raining, 1.5 Hours
No Wet Stream Crossings
Stay Out
50 – 54°C
7 Hours If Raining, 2 Hours 8 Hours If Raining, 4 Hours
5 Hours If Raining, 2.5 Hours
3 Hours If Raining, .5 Hour
5 Mins.
7 Hours If Raining, 3.5 Hours
3 Hours If Raining, 1 Hour
5 Mins.
60 – 64°C
9 Hours If Raining, 4.5 Hours
8 Hours If Raining, 4 Hours
12 Hours If Raining, 3.5 Hours
10 Mins.
65 – 69°C
12 Hours If Raining, 6 Hours
12 Hours If Raining, 6 Hours
12 Hours If Raining, 6 Hours
10 Mins.
> 70°C
No Limit
No Limit
No Limit
30 Mins.
55 – 59°C
INDICATIONS OF INCREASED SUSCEPTIBILITY Subjects initially were unable to remain in cold room for 4 hours
After a 48 hour recovery period with refeeding and rest, cold tolerance improved significantly
November Over 24 Hours in Jungle Phase 39
101
Early morning body temperatures dip
38
100 99
37 98 97
36 Daytime activities drive body temperature up 35 9:00 12:00 15:00 18:00 21:00 0:00 3:00 Time of Day
96 6:00
9:00
95
• Using temperature “pill” technology with beltworn recorders, new data has been obtained on body temperature changes in field training. These tests will ensure approved immersion times do not drop core temperatures lower than predicted.
MILITARY COLD RESEARCH
10°C
• Ranger students transported to a lab in Pensacola immediately after the end of the jungle phase had a special susceptibility to cold with altered physiological responses
102
(Fahrenheit)
Ankle Deep Water
Body Temperature (Centigrade)
Temperature Reading (Air or Water)
AUTOMATED WARNING SYSTEM
• A series of lab studies have isolated factors such as repeated immersion and recent exercise which increase cold injury risk
• An automated system using realtime environmental monitoring and accurate cold (and heat) injury prediction will replace tables
17
NUTRITIONAL ADEQUACY OF RATIONS Operational rations have been tested in Ranger training to determine the nutritional adequacy of the formulations even in high stress applications. It was hypothesized that Ranger students would demonstrate deficiencies of one or more specific nutrients as a result of the extensive food restriction during the course. There were even special provisions in the research plan setting limits on blood sampling as anticipated reductions in iron and red blood cell concentrations fell below certain limits; this never happened. The surprising result was that all biochemical measures and indices of nutritional status and health remained within normal limits. Some Ranger students used a daily multivitamin supplement (one vitamin pill per day was permitted by the cadre), but even students using no supplements demonstrated normal vitamin status. Detailed physical examinations intended to reveal any signs of vitamin or nutrient deficiencies revealed underfed but otherwise healthy men. The MRE and the Long Range Patrol (LRP) ration were tested as the single source of subsistence for 710 day periods during the training. All measurements remained within normal limits and some indices of vitamin status even improved, confirming the generous vitamin and nutrient fortification of these rations. They were, of course, inadequate for energy requirements but could be approved for use by soldiers on weightlimited patrolling activities for 1014 day periods. A more recent study with cadre from the Camp Merrill participating in a grueling endurance challenge, proved the value of a carbohydrate drink supplement compared to a flavored lookalike which did not provide additional carbohydrate. This is one of the studies which contributed to the fielding for Army use of the ERGO drink and HOOAH! bar. Even with limited food intakes, Ranger students maintained remarkably normal nutritional status, based on many sophisticated tests performed at the end of patrolling exercises before refeeding occurred.
18
NUTRITIONAL ADEQUACY OF RATIONS Restricted ration concepts which provide all necessary nutrients but trade off adequate energy intake for weight and bulk in a long range patrol were tested in Ranger training
The Meal, ReadytoEat, Individual (MRE) provides 1350 kcal (13% protein, 36% fat, and 51% carbohydrate) and is to be served as three meals per soldier per day. In the 1991 study, the MRE, served to Ranger students as one meal per day for up to 10 days at a time, was found to be nutritionally adequate (except for total energy).
Nutritional Assessments Made on Blood Samples During Ranger Training: Energy & Nitrogen Metabolism Serum Iron and Red Blood Cell Status Iron Glucose TIBC Lactate Transferrin Saturation Urea Nitrogen Ferritin Creatinine Red Cells Total Protein Hemoglobin Albumin Hematocrit Glycerol Fatty Acids Indices of Vitamin Status for: Hydroxybutyrate Retinol (Vitamin A) Serum Enzyme Markers LDH GGT ASAT ALAT Bilirubin Serum Mineral & Electrolytes Calcium Phosphorus Magnesium Sodium Potassium Chloride
Vitamin B 12 Folate (Plasma & Red Cells) Ascorbic Acid (Vitamin C) Vitamin D Thiamin Riboflavin (Vitamin B 2 ) Pyridoxamine (Vitamin B 6 )
The Food Packet, Long Range Patrol (LRP) provides 1560 kcal (15% protein, 35% fat, and 50% carbohydrate) for limited use of one packet per soldier per day for up to 10 days at a time. The nutritional adequacy of the LRP, combined with a pouch bread, was demonstrated in the 1992 study.
• A separate study using Ranger school cadre led to the fielding of the HOOAH! bar and ERGOdrink (carbohydrate supplements)
Special exams for nutritional deficiencies revealed no problems except simple weight loss
19
RECOVERY FROM RANGER TRAINING An important question frequently raised about intensive small unit operations is how quickly do individuals recover and how soon can they begin the next mission. The Ranger course provides a worst case scenario to address this question. There has also been some concern about whether or not Ranger students have any long term harm as a consequence of their exposure. The first recovery study involved extensive laboratory evaluation of eight graduates from the 1991 study six months after the end of their course. The men were found to be returned to peak physical condition and health. Based on individual interviews, problems were determined to be most common in the first 46 weeks after training. Following the 1992 study, 9 graduates still at Fort Benning one week after the course were interviewed and gave blood samples. Metabolic hormones and other biochemical measures were completely restored to normal. Diarrhea and nausea, related to overeating, were common complaints. Sleep measurements using actigraphy in the first week after training demonstrated persistently disrupted sleep patterns. Ten other graduates of the 1992 study were evaluated in the laboratory using many of the same measurements made during the course and duplicating all of the measurements made in the 1991 6month post training study. The most remarkable finding was an average increase in body fat which exceeded individual levels at the start of the Ranger course by 50%. There were continued problems of uncontrollable eating urges and some sleep disturbances. Other measurements were returned to normal including lean mass and muscular strength. These studies showed that the greatest challenge to recovery following Ranger training was to get appetite under control. For many students the overshoot which occurs in the recovery of body fat may be unavoidable, but after the first month this begins to adjust back down to previous levels. One month after the end of the course, average body fat rose to 150% of body fat measured at the start of the course and Rangers reported continuing problems of uncontrollable eating surges and sleep disturbances.
20
RECOVERY FROM RANGER TRAINING Students who successfully completed the course with the study groups were invited to the USARIEM lab for posttraining recovery studies. RANGER COURSE (8 Weeks) Students Measured and Tested at Start of Course
• Students arrive for Ranger training in peak condition
Intensive Studies
RECOVERY STUDY PERIOD (6 Months) 1992 1992 Blood Tests, Blood Tests Physical Only Measurements, (1 Week Post) Physical Exam (5 Weeks Post)
1991 Blood Tests, Physical Measurements, Physical Exam (6 Months Post)
• Diarrhea and nausea from overeating
• Abnormally increased appetite (hyperphagia)
• Hormone levels returned to normal
• Sleep disturbances
• Students completed the course with most body fat gone and metabolic adaptations geared to starvation survival
• 50% higher body fat than at start of training • Strength, lean mass, and biochemical measures returned to normal
* On the first day after Ranger school, eating was the first priority, sleeping was the second
• Rangers returned to peak health and fitness (except for residual toe numbness)
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FUTURE RESEARCH Ranger training provides an opportunity for military medical researchers to understand the impact of operational stressors on soldier health and performance. This will lead to development of useful interventions which will make Ranger and other high intensity training safer and improve effectiveness of the whole force. Current concepts for minimally invasive “wearandforget” physiological sensors that continuously monitor soldier health and performance will benefit from tests in high intensity training such as the Ranger school and, in turn, Rangers may be early adopters of the technologies. A variety of sensors currently exist and engineering technology is not the limiting step; the challenge is to determine how to interpret the information from sensors so that useful warning can be provided to commanders (instead of raw data such as heart rate). The current need in this area is for large amounts of data on many different individuals in extreme and varied training environments. This allows identification of the physiological signals which reliably predict specific health and performance outcomes. Realtime physiological sensing will provide soldiers and their commanders information about readiness status. The greatest challenge in this research is to provide useful interpretation of biomedical signals.
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FUTURE RESEARCH Data Fusion Strategies: Accurate estimates of physiological status are expected to require sophisticated analyses of change through time, interpreting evolving datasets on the basis of unit and mission characteristics. The MERCURY system, in place at the Florida Ranger training camp, is an example of data fusion involving realtime weather data and physiological models; individual soldier data will eventually merge realtime biological input
Sensors: Temperature “Pill”, Actigraph, Foot Strike Monitor
with the meteorological context. • Certain parameters such as dehydration and mental functioning will be directly useful to ensuring safe and effective future Ranger training • The Ranger course offers important test opportunities to collect data necessary to develop soldier health and performance predictions
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REFERENCE PUBLICATIONS The scientific publications listed below are the result of over two decades of studies performed with the cooperation of the Ranger Training Brigade at Fort Benning, Georgia. Through these studies, the Army and other services have been able to develop guidelines for protection from injury and infection during high stress training. Significant Reports of Data from Biomedical Studies of the Ranger Course (chronological) Consolazio FC, LO Matoush, RA Nelson, RS Harding, JE Canham. Nutrition survey: Ranger Department, Fort Benning, Georgia. Laboratory Report No. 291, U.S. Army Medical Research and Nutrition Laboratory, Fitzsimmons General Hospital, Denver, CO, 1966. Johnson HL, HJ Krzywicki, JE Canham, JH Skala, TA Daws, RA Nelson, CF Consolazio, PP Waring. Evaluation of calorie requirements for ranger training at Fort Benning, Georgia. Institute Report No. 34, Letterman Army Institute of Research, Presidio of San Francisco, CA, 1976. Pleban RJ, PJ Valentine, DM Penetar, DP Redmond, GL Belenky. Characterization of sleep and body composition changes during Ranger training. Military Psychology 1990;2:145156. Moore RJ, KE Friedl, TR Kramer, LE MartinezLopez, RW Hoyt, RE Tulley, JP DeLany, EW Askew, JA Vogel (1992). Changes in soldier nutritional status & immune function during the Ranger training course. Technical Report No. T1392, September 1992, US Army Research Institute of Environmental Medicine, Natick, MA. 162 pp. Nutritional Assessment of U.S. Army Ranger Training Class 11/91. Letter Report. Workshop proceedings of the Committee on Military Nutrition, National Academy of Sciences, Washington DC, 57 Feb 1992. MartinezLopez LE, KE Friedl, RJ Moore, TR Kramer. A prospective epidemiological study of infection rates and injuries of Ranger students. Military Medicine 1993;158:433437. Friedl KE, JA Vogel, LJ Marchitelli, SL Kubel. Assessment of regional body composition changes by dualenergy xray absorptiometry. pp. 99103. In: Human Body Composition, K.J. Ellis & J.D. Eastman (eds). New York: Plenum Press, 1993. Moore RJ, KE Friedl, RT Tulley, EW Askew. Maintenance of iron status in healthy men during an extended period of stress and physical activity. American Journal of Clinical Nutrition 1993;58(6):923927. Askew EW, RJ Moore, KE Friedl, RW Hoyt (1993). Nutritional status and body composition changes during sustained physical work and calorie deprivation. Experimental Biology 93, 28 Mar1 April 1993, New Orleans, LA. [published abstract: FASEB Journal 7(3): A613 (#3550)]. Hoyt RW, RJ Moore, JP DeLany, KE Friedl, EW Askew (1993). Energy balance during 62 days of rigorous physical activity and caloric restriction. Experimental Biology 93, 28 Mar1 April 1993, New Orleans, LA. [published abstract: FASEB Journal 7(3): A726 (#4194)]. Marriott BM (editor). Review of the Results of the Nutritional Intervention, Ranger Training Class 11/92 (Ranger II). Workshop proceedings of the Committee on Military Nutrition, National Academy of Sciences, Washington DC, 1517 Mar 1993. Washington DC: National Academy Press, 1993. 226 pp.
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Significant Reports of Data from Biomedical Studies of the Ranger Course (chronological) (continued) Frykman PN, BC Nindl, KE Friedl, EA Harman, RL Shippee (1993). Effects of extended physical training and caloric deficit on power output of young healthy males. American College of Sports Medicine 40th Annual Meeting, 25 June 1993, Seattle, WA. [published abstract: Medicine and Science in Sports and Exercise 25 (suppl): S58 (#323)]. Johnson MJ, KE Friedl, PN Frykman, RJ Moore. Loss of muscle mass is poorly reflected in grip strength performance in healthy young men. Medicine in Science & Sports and Exercise 1994;26(2):235240. Friedl KE, RJ Moore, LE MartinezLopez, JA Vogel, EW Askew, LJ Marchitelli, R Hoyt, CC Gordon. Lower limits of body fat in healthy active men. Journal of Applied Physiology 1994;77(2):933940. Shippee L, K Friedl, T Kramer, M Mays, K Popp, E Askew, B Fairbrother, R Hoyt, J Vogel, L Marchitelli, P Frykman, L MartinezLopez, E Bernton, M Kramer, R Tulley, J Rood, J DeLany, D Jezior, J Arsenault (1995). Nutritional and immunological assessment of Ranger students with increased caloric intake. Technical Report No. T955, Dec 1994, US Army Research Institute of Environmental Medicine, Natick, MA. 212 pp. Bernton E, D Hoover, R Galloway, K Popp. Adaptation to chronic stress in military trainees. Adrenal androgens, testosterone, glucocorticoids, IGF1, and immune function. Annals of the New York Academy of Sciences 1995;774:217231. Friedl KE, MZ Mays, TR Kramer, RL Shippee (1995). Acute recovery of physiological and cognitive function in U.S. Army Ranger students in a multistressor field environment. In: NATO AC/243 Panel VIII, Workshop on the effect of prolonged exhaustive military activities on man. NATO Technical Report. 35 April 1995, Holmenkollen, Oslo, Norway. Hodgdon JA, KE Friedl, MB Beckett, KA Westphal, RL Shippee. Use of bioelectrical impedance analysis measurements as predictors of physical performance. American Journal of Clinical Nutrition 1996;64(suppl):463S468S. Nindl BC, KE Friedl, LJ Marchitelli, RL Shippee, CD Thomas, JF Patton. Regional fat placement in physically fit males and changes with weight loss. Medicine and Science in Sports and Exercise 1996;28(7):786793. Kramer TR, RJ Moore, RL Shippee, KE Friedl, L MartinezLopez, MM Chan, EW Askew. Effects of food restriction in military training on Tlymphocyte responses. International Journal of Sports Medicine 1997;18:S84S90. Friedl KE. Variability of fat and lean tissue loss during physical exertion with energy deficit. pp. 431450. In: JM Kinney and HN Tucker (eds), Physiology, Stress, and Malnutrition: Functional Correlates, Nutritional Intervention. New York: LippincottRaven Publishers, 1997. Nindl BC, KE Friedl, PN Frykman, LJ Marchitelli, RL Shippee, JF Patton. Physical performance and metabolic recovery among lean, healthy men following a prolonged energy deficit. International Journal of Sports Medicine 1997;18(5):317324. Young AJ, JW Castellani, C O’Brien, RL Shippee, P Tikuisis, LG Meyer, LA Blanchard, JE Kain, BS Cadarette, MN Sawka. Exertional fatigue, sleep loss, and negative energy balance increase susceptibility to hypothermia. Journal of Applied Physiology 1998;85:12101217. Costello R, S CarlsonNewberry (editors), Military Strategies for Sustainment of Nutrition and Immune Function in the Field. National Academy Press, Washington DC, 1999. Friedl KE, RJ Moore, RW Hoyt, LJ Marchitelli, LE MartinezLopez, EW Askew. Endocrine markers of semistarvation in healthy lean men in a multistressor environment. Journal of Applied Physiology (in press, 12/99).
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Additional copies of this booklet are available from the Military Operational Medicine Research Program Fort Detrick, Maryland, USA
Prepared by: LTC Karl E. Friedl, Ph.D. Janet G. Reese, Anteon Corporation
Military Operational Medicine Research Program Fort Detrick, Maryland, USA 1999
