Part II
Questions Posed to the Committee, Answers and Discussion
In the following section the five questions posed to the committee are specifically answered. After each answer the CMNR presents an overview of their reasoning and rationale, as well as their recommendations as they relate to the question posed. The CMNR recognizes that this was an operational study and that complete control over all experimental variables was not always possible.
Question 1: Was the nutrition intervention (increasing energy provision by 10-15%) effective in decreasing medical risk?
Answer: The outcomes from Ranger II were different from Ranger I. In addition to the increase in energy provision, other interventions were introduced in Ranger II. Ranger I and II were not done simultaneously, thus the possibility of alterations in behavior of both cadre and students is present. In Ranger II, this may have resulted in increased attention to provision of food and/or water and increased vigilance directed towards preventing health related problems based on lessons from Ranger I.
In the Ranger II study the following interventions differed from the Ranger I study:
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there was increased energy intake throughout the Ranger II study;
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there was an increase in protein intake during the field training exercises in Ranger II;
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the sequence of training sites was changed;
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field rations were changed at mid point of Ranger II;
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there was an increase in activities, voluntarily or involuntarily during Ranger II, as determined from increased energy expenditure;
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anecdotally, there were suggestions that there was an increased use of knee pads or perhaps other protective coverings that may have affected the number of abrasion, punctures, etc. suffered by soldiers in Ranger II; and
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additional testing, in particular the cognitive function tests, were added to the Ranger II study.
The following outcome differences were noted:
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Ranger II trainees exhibited increased energy intake and increased energy expenditure when compared with the Ranger I trainees;
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body weight and percent body fat were preserved to a greater extent in the Ranger II study;
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the high frequency of extremely low levels of percent body fat that were seen in the Ranger I trainees were not observed in Ranger II;
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the incidence of cellulitis (on the knees, legs, ankles, feet, hands, or multiple locations) was higher in the Ranger I study than in Ranger II; and
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decline in immune function (IL-2, lymphocyte proliferation) was relatively better preserved in Ranger II when compared with Ranger I.
Because more than energy intake changed in Ranger II, it is not possible to attribute all of the outcome differences between the studies specifically to the differences in nutrition. However, it is quite likely that the increased energy intake played a major role in the improvements noted above.
Discussion: It was fortunate that the study design in Ranger II allowed measurements following a short refeeding episode at the Mid-Mountain Phase. Data from this assessment demonstrated rapid improvement in some of the measures of immune function, hormone levels (e.g. testosterone and insulin like growth factor), and some aspects of cognitive performance. These findings suggest that provision of periods of adequate energy intake and sleep can dramatically improve both mental and physical performance. They give credence to the possibility that the improved outcomes in Ranger II were due in major part to the increased baseline energy provided.
Small losses of body fat imply loss of other bodily constituents and signal a state of metabolic deprivation. There is reason for concern when losses result in a total body fat of less than 10%, especially when losses are rapid. At the final sampling during the Ranger II study there were some individuals with less than 10% body fat. This suggests that some soldiers may continue to be at medical risk of emaciation. Even though immune functions were minimally improved in Ranger II, the possibility of increased health risk for individuals
with less than 10% body fat is supported by the continued evidence of multiple impairments in immune functions.
The CMNR is concerned that while information is limited to only a few subjects in the follow-up studies, anecdotal reports indicate that a significant percentage of soldiers reported problems with diarrhea during refeeding. This observation should be followed up on a broader basis as this may indicate that there was some compromise of gut function and/or impaired immune function. Ideally, if further evaluation indicates this to be a widespread problem, an assessment of the problem should be included as a follow up to additional Ranger studies, possibly even through a carefully controlled study in a metabolic unit.
Recommendations: To further address the question of medical risk, the CMNR recommends that comprehensive studies be conducted in a small number of subjects, beginning immediately after their Ranger training has been completed. The subjects should include men with the highest percentages of losses in body weight and body fat.
The post-training studies should include measurements of nutritional and relevant physiological parameters to assess the magnitude of losses in muscle protein mass and function, of lean body mass, and of other nutrient stores. Attempts should also be made to estimate the time required to restore any observed deficits in body nutrient stores.
Attention should be given also to the refeeding diarrhea observed after training, with respect to its possible etiology, the possible presence of steatorrhea, and to the duration of diarrhea.
Nutritionally induced dysfunctions of the immune system usually respond promptly to refeeding. This could be assessed by performing an additional battery of delayed dermal hypersensitivity tests, beginning 7-10 days after the onset of refeeding.
In both Ranger I and II an increase was observed in the battery of enzymes associated with liver function. The cause of this increase should be explored through further research. For example, these enzymes may be derived from muscle tissue and may be associated with the loss of lean body mass. This could be ascertained in a subsequent study of Ranger Training by not only measuring the liver enzymes as in Ranger I and II but also by determining specific isoenzymes of LDH, AST, and ALT at the beginning and end of the Mountain Phase. Data collection on these enzymes and isoenzymes at these time points would provide information before and after the most grueling periods of Ranger Training.
Question 2: Should an even greater increase in energy intake be recom mended (consistent with Ranger training goals)?
Answer: It is impossible to answer this question definitively with the data available. However, the results of Ranger II compared with Ranger I suggest a beneficial effect of the increased caloric intake in Ranger II in minimizing loss of body weight and body fat stores. The decrement in physical performance observed in Ranger II was similar to that observed in Ranger I. In contrast, cognitive performance appeared improved during periods of refeeding and additional sleep (Mid-Mountain Phase). However, no direct comparison with Ranger I is possible since data were not collected at a comparable refeeding time. Overall, the caloric supplement appeared compatible with Ranger goals. The value of additional increases in energy intake requires further study.
Discussion: The increase in calories provided in Ranger II compared to Ranger I appeared to have a beneficial effect with regard to minimizing body weight loss and excessive depletion of body fat stores. It appeared however, that performance decrements measured by lift capacity were not systematically changed by the extra caloric supplement provided in Ranger II.
According to the data presented, there was an increased level of energy expenditure in Ranger II versus Ranger I. Although the experimental conditions were not identical, the additional energy intake may have been responsible. This result is similar to that seen in populations where there is an increase in voluntary activity when energy intake levels increase after long-term consumption of sub-optimal energy intakes. In trying to have periods of adequate energy intake included in the training, it may be necessary to take into account an increased level of energy expenditure if kcal intake levels are increased.
Some aspects of cognitive function improved with refeeding and additional sleep (Mid-Mountain Phase). To control for possible differences in initial body weight and body composition, it would be valuable to present data comparing Ranger I and II by including data for each individual for body weight, body fat and lean body mass, pre- and post-study. The data provided suggest a beneficial effect of dietary supplement but the continued decrements in physical and cognitive performance suggest that further increases in caloric intake might well lead to improved learning and performance. In future studies this could be tested by studying sequential Ranger groups in a dose response fashion (two levels of caloric increment or periodicity).
Recommendations: Consistent with Ranger goals the degree of stress required needs continuous reassessment. Based on the outcome of that
assessment, periodic refeeding during the course should be considered as a means of enhancing cognitive functioning and work performance. The data from Ranger II with regard to the Mid-Mountain Phase suggest that repeated periods of acute as opposed to chronic caloric deprivation stress are tolerated better by the trainees. These data could also provide suggestions for future studies of acute versus chronic deprivation and performance. Future studies of Winter Rangers who receive higher levels of caloric intake might provide some of these data.
The apparently beneficial effect on cognitive performance of refeeding must be assessed independently of possible beneficial effects of additional sleep (Mid-Mountain Phase). Future designs could separate these effects.
Question 3: Should any specific supplementation of vitamins, minerals, or protein be considered?
Answer: No. The data provided do not suggest any problems with regard to vitamin or mineral nutriture (with the possible exception of hyperzincemia, which was noted as a group mean value in Ranger II). However, there is some question about the adequacy of the actual intake of protein during the field phases.
Discussion and Recommendations: The micronutrient content of the rations appears to be adequate. Nevertheless, some Rangers chose to supplement with vitamins and minerals which they brought to the training program. In additional data analyses, if possible, individuals who used supplements should be compared with those who did not. Future studies of Ranger Training might also consider this as a design point.
Since no information was provided regarding protein intakes during Ranger II as compared to Ranger I, it is difficult to determine if protein intake was “adequate” during all phases of either study. The more hypocaloric the state of the individual, the more protein will be required to minimize negative nitrogen balance. Therefore, the question of protein intake is relevant in considering the data from Ranger II. Supplementation with either additional protein or energy should decrease fat-free mass loss due specifically to lack of protein rather than that due to inadequate energy, particularly at high levels of energy expenditure. It is difficult to ascribe the small reduction in loss of fat-free mass between Ranger I and II to the increased energy intake without knowing if protein intake was held constant or was similar between the two studies. This does not seem to have occurred due to the difference in protein content between the MRE fed in field training exercises in Ranger I for 33 days and the MRE or LLRP plus pouch bread (which provided an additional
12-16 g of protein) fed for 38 days during the field training exercises in Ranger II. Nutrient intake and balances, where they are possible to estimate, should be evaluated, particularly with reference to protein. In addition, changes in the hydration state of the fat-free mass would also have to be taken into consideration to assess changes in protein mass.
The data for all nutrients presented at the meeting were group means. To address the issue of supplementation, especially additional protein, the individuals who were in the extreme quartiles of the distribution for body fat/fat-free mass before and after participation in the program need to be evaluated. For example, will there be an invariant loss in lean body mass? Concerns with possible misidentification of water as lean body mass using dual-energy x-ray absorptiometry (DEXA) methodology suggests that lean body mass loss could be even greater than reported. Perhaps this will be clarified when the doubly labeled water data is available for comparison with the other methodologies used in the study.
The elevated plasma zinc concentrations, noted as a group average during Ranger II, are most unusual and unexpected. In stressful situations of many varieties, plasma zinc values typically decline as a result of zinc sequestration in the liver, where zinc becomes bound to metallothionines, newly induced by cytokines such as IL-1.
Hyperzincemia is a rare and unusual finding, with few known causes. Most commonly, high zinc values are factitious, and caused by zinc contamination of the samples, with needles being a source of the zinc. Familial hyperzincemia is an exceedingly rare condition, and can be discounted as a possibility here. Ingestion of excess zinc can lead to hyperzincemia of several hours duration, and may be an explanation in the Rangers, who were allowed to take unregulated amounts of vitamin/mineral supplements. Many such supplements are known to contain large amounts of zinc. A last possibility is associated with the escape of cellular enzymes into the plasma; many enzymes contain zinc.
The cause of the hyperzincemia can be investigated: a) by checking the needles used in blood sampling to see if they leach out any zinc; b) by reviewing blood collection methods to search out any other cause of zinc contamination; c) by reviewing data of individual Rangers to see if hyperzincemia in a few caused group mean values to be elevated; d) by contacting individuals with hyperzincemia to determine if they took zinc-containing supplements, and finally; e) by reviewing the high enzyme values to determine if any of the enzymes were zinc containing ones.
Future studies would be necessary to assess the value of performance enhancing supplements such as amino acids (e.g., tyrosine, tryptophan, arginine, glutamine), vitamins (e.g. choline), minerals (such as potassium), or other substances such as caffeine, nicotine, etc. Pilot studies (before Ranger
field studies) should be used to assess the value of supplements. Muscle biopsies also could be performed in these pilot studies.
Question 4: Are the immunological changes noted related to the plane of nutrition during Ranger training or to other (e.g. sleep deprivation) stressors?
Answer: Some immunological changes noted during Ranger II can clearly be caused by the decreased plane of nutrition. Other concomitant stressors (including loss of sleep; severe, prolonged, and repeated muscular exertion; dermal inflammation and abrasions; and minor infections) could also contribute to the observed immune system derangements.
Discussion: The immunological studies reported by Dr. T. R. Kramer (USDA), CPT R. J. Galloway (WRAIR), and LTC E. W. Bernton (WRAIR) all showed reassuring internal consistency during Ranger II. Further, these new data reflected quite well the various immune system changes seen during Ranger I.
Dr. Kramer's studies in both Ranger I and II, showed reductions in T-lymphocyte functions. These were evidenced by decreased proliferation of Total, Helper, and Suppressor T-cells. Changes were also noted in the cytokines. The in vitro release of soluble receptors for IL-2 was reduced. Decreases in plasma IL-6, and decreases in the in vitro cellular release of IL-6 were noted also. The immunological decrements found by T. R. Kramer in Ranger II were not quite as large as those seen in Ranger I. The possibility that this between-study difference was due to the increase in food intake during Ranger II was strengthened by findings that transient improvements in all measured T-cell populations occurred immediately after the brief increase in food intake during the first days of the Mountain Phase of Ranger II.
Sleep deprivation was similar during Ranger I & II, and presumably, this stress should have influenced the immune system equally in the two studies. However, the incidence of infections and dermal abrasions during Ranger II was decreased. The reduction of these stressors in addition to the smaller losses of body weight and nutrient stores could, in combination, have contributed to the relatively better preservation of T-cell numbers and functions. The unregulated consumption of vitamin/mineral preparations could also have contributed to the slightly smaller immune system dysfunctions observed in Ranger II.
LTC Bernton's data showing progressive decreases in delayed dermal hypersensitivity (DDH) responses during Ranger II were quite similar to the DDH data he had obtained in earlier Ranger groups. These in vivo data give
strong evidence for a progressive (eventually quite marked) reduction in cell mediated immunity as multiple stresses accumulated during the 4 phases of training. The reduction in DDH responsiveness could be attributed to the progressive losses of body weight and nutrient stores, as seen in the Ranger trainees, as well as to the other stressors they experienced. However, the contribution of each stressor cannot be differentiated. The increase in food intake during Ranger II did not seem to reduce the measured decrements in DDH responsiveness. Although reductions in DDH responsiveness in Ranger II were shown to correlate with reductions in plasma testosterone and TSH values, this does not prove that a “cause-and-effect” relationship exists between these variables.
LTC Bernton's work also included observations on increases in leukocyte production of superoxide radicals during Ranger II, but also a poorer production of Tumor Necrosis Factor (TNF), a cytokine that triggers acute-phase reactions, and Serum Amyloid A (SAA), an acute-phase reactant protein.
Studies in the Rangers did not attempt to determine if changes occurred in Natural Killer T-cell numbers or functions. These are also highly important components of cell mediated immunity. Further, immunological studies during Ranger II did not attempt to measure any responses involving cellular antigen-presenting activities or B-cell functions. These are important components of humoral immunity. Administration of vaccine antigens in an earlier Ranger study indicated that deficiencies in humoral immunity developed during the course of training.
The possible occurrence of cytokine-induced “acute phase reactions” has not been adequately documented during Ranger studies. This is an important immunological and nutritional question. The increased body temperatures, hypermetabolism, losses of body weight, and muscle mass that are components of the “acute phase reactions” associated with infections, inflammation, and/or severe muscular work could play a part in the losses of body weight and stored nutrients, as seen during Ranger training.
Some indirect evidence for the occurrence of “acute phase reactions” was seen in Ranger I studies. However, the poor cellular production of IL-6 and TNF in Ranger II studies would suggest that “acute phase reactions” were not of major concern in contributing to the observed weight loss. The lowered body temperature measurements (LTC Bernton 's data) at the end of Ranger II are also incompatible with an “acute phase response”, but they are quite compatible with physiologic responses to prolonged semi-starvation and body weight loss.
In conclusion, the minimal lessening of immune system dysfunctions during Ranger II would probably contribute very little to an overall improvement in resistance against infectious illnesses. At least some of the immunological changes noted during Ranger II could clearly be identified as being
related to a decreased plane of nutrition. Other concomitant stressors, including loss of sleep; severe, prolonged, and repeated muscular exertion; dermal inflammation and abrasions; and minor infections, would all combine to produce immune system changes.
Recommendations: Useful additional information could possibly be gained by:
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comparing the weight loss and body fat loss of individual Rangers with their various immunological measurements; this should include individual data from both Ranger I and II, and should emphasize the individuals with greatest weight (fat and lean) and nutrient losses as well as those with the largest immune dysfunctions; and
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adding any data available on the drop-outs to these comparisons, as these data may also prove useful.
If future Ranger Studies are possible, additional data should be gathered on:
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antibody responses to new antigens at various times in the progressively developing immunosuppression;
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possible changes in Natural Killer Cell numbers and functions;
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longitudinal development of body core temperature changes using the tympanic membrane thermoscan technique; and
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baseline and periodic longitudinal studies of key “acute-phase” cytokines, i.e., IL-1, IL-6, and TNF.
Question 5: Are the decrements in cognitive function a cause for concern?
Answer: Despite impressive evidence gathered during this study suggesting that the regimen of Ranger training results in decrements in several areas of cognitive function, it would be premature at this time to draw definitive conclusions and attempt to answer this important question on the basis of data collected during a single study. Further, because a particular cognitive deficit may be of little significance to successful performance in one situation but critical to performance in another, the answer to this question requires a full consideration of the nature of activities in which the student is engaged during training.
Discussion and Recommendations: The data show relatively strong effects of the Ranger training regimen on several aspects of cognitive function, including a 33% decrement in decoding speed, a 7% decrement in memory
accuracy (no speed trade-off possible), a 20% decrement in reasoning speed, and a 15% decrement in visual attention (speed and accuracy). Performance decrements were observed beginning with the second phase (Desert) and continued throughout. In particular, attention to detail and concentration were substantially impaired and showed a cumulative effect over the course of training. Visual attention and memory performance did show improvement with a brief recovery period (Mid-Mountain Phase), but performance on decoding and reasoning tasks did not respond to this intervention. Further, although individual data were not reported, measures of variability in performance were relatively small, indicating that these effects were present to a similar degree in all students. Decrements were therefore found to occur even among the most highly motivated individuals. In addition, a trade-off between the time required to perform a task and the accuracy of performance was observed across tasks; the strategy apparently adopted by the student was to attempt to maintain accuracy and minimize error at the expense of increasing response time.
Notwithstanding these impressive findings, this study represents only the first attempt to systematically assess the effects of Ranger training on cognitive function and performance and it is unknown whether the same effects occur in other classes, and if so, to what degree. It is also unknown whether other, yet unmeasured, aspects of psychological and cognitive function necessary for effective performance might be negatively impacted by the stressors experienced during this type of training. Further, several factors that might mediate the functional effects of these stressors, such as student expectations, feedback (awareness of performance decrements), and debriefing, need to be more fully considered. Therefore, data from the present study alone are not adequate to fully answer the question posed to the committee.
Whether those decrements in cognitive performance which ultimately prove to be reliable are sufficiently critical, broad or severe to be a cause for concern is largely dependent on the nature of the activities in which the student is engaged. Ranger training is designed to test the physical and psychological limits of the student under conditions which simulate the demands of combat (i.e., in the presence of multiple severe stressors) and to develop in the student leadership skills important to the accomplishment of all assignments. One objective is to create an awareness in the student, through personal experience as well as observation, that chronic stressors (e.g., extended food or sleep deprivation) will affect mental as well as physical performance. Potential leaders must also develop an awareness that such stressors will compromise the capabilities of even the most motivated soldier. As one researcher noted, despite expectations to the contrary, “ There are no supermen.” Therefore, it is critical that the training regimen continue to include stressors which result in decrements in cognitive function. However, it must
be determined that these effects are transient and will recover with removal of the stressor(s). Further, these decrements in cognitive function should not be induced in severe degree at a time when the safety of the individual student or the group might be compromised, such as during helicopter evacuations. Because performance on attention and short-term memory (decoding) showed recovery with refeeding and additional sleep (mid-Mountain), some concern might be alleviated by including a short recovery period just prior to particularly dangerous and demanding exercises.
Replicating the findings of Ranger II, broadening the range of cognitive functions assessed, and investigating potential mediating factors such as those discussed above should permit a relatively confident response to this important question.
The committee was impressed with the documentation of psychological and behavioral effects in this study. The rationale for selection of individual tasks was theoretically and experimentally sound, and appropriately selected for use in field situations. Tasks chosen for administration were decoding, memory, reasoning, and embedded figures. These tasks varied in their emphasis on attention (automatic versus effortful), memory and judgment, and in their reliance on visual information processing, the ability to check (correct) work, and the availability of feedback to the student. Collectively, this battery of tasks was sufficiently broad to assess a range of cognitive function. The functions studied also appear to be relevant to tasks routinely required of the soldier. Clearly, this type of information should continue to be collected in future studies of Ranger training and the results shared with Rangers during debriefing.
The committee agrees with the recommendation of the principal researcher, MAJ Mays, that scheduling brief periods of recovery should be considered for possible implementation. A hot meal and 8-10 hours of sleep could provide a more desirable balance between the competing goals of maintaining a high level of stress in the student while permitting him to learn about the physical and functional consequences of both acute and chronic stressors through personal experience and observation. Further benefit in this regard could probably be achieved by providing the student with immediate feedback on his cognitive performance during training, and, at the conclusion of training, engaging all students in an extensive discussion of the functional consequences of stressors like food and sleep deprivation, using their own data and those of the cadre as examples, and the implications of these effects for cognitive performance during combat or other demanding assignments.
Future studies should determine the extent to which students are aware of increasing difficulties with their mental performance, and the impact of this knowledge on their confidence, motivation, and performance on future tasks. A related question is whether performance decrements in a student influence
that student's perception of performance decrements in other students. How performance decrements are perceived by others in the unit and whether such decrements cause others to question a student's leadership skills, should be addressed.
To what extent the observed accuracy-for-speed trade-off occurs naturally, or is the result of instructions to minimize error, is not known. Regardless, what implications does such a strategy have for performance of assignments which emphasize time? How flexible is this student 's approach to tasks with varying emphasis on accuracy and speed?
Future studies should also consider inclusion of additional cognitive tasks to converge on specific cognitive processes (constructs) thought to be most susceptible to the effects of caloric and sleep restriction, and should consider assessment of other modalities, e.g., auditory based tasks.
Procedural questions which were not addressed but should be considered include the following. How should students be prepared for cognitive and physical performance decrements (i.e., What are their expectations)? Should students be told that mental processes including memory and reasoning will be significantly influenced by the training regimen? Should students be debriefed and what is the nature of this debriefing? Would extensive discussion of cognitive (and emotional) effects of the physical and psychological stressors following the course be beneficial?
Through combining the results on sleep deprivation from the two Ranger studies with the cognitive data from Ranger II, the scientists involved in the studies could make suggestions to the Ranger Training Brigade. These suggestions could be utilized by the Ranger cadre during the first days of training to provide the trainees with strategies to optimize their success in terms of sleep and learning. Based on the results from the two Ranger studies, the opportunity exists for future Ranger classes to begin their training with suggested strategies to maximize opportunities for sleep. Given a short sleep period, based on data from the Ranger studies, how should trainees optimize their sleeping time to obtain quality sleep? Similarly, given the sleep deprived state of all trainees, what strategies can be used to maximize learning and mental performance, based on the data from Ranger II? These types of information would put the data collected during these studies to good use to directly enhance the performance of Ranger trainees. It would also provide the opportunity in a future Ranger Study to study the impact of such recommendations.
An issue raised following the previous Ranger study was: How much stress is required to meet program objectives (training goals)? Assuming the stressors imposed during Ranger training are operationally defined, this question will remain unanswered until objectives are stated in a manner which is amenable to establishing quantifiable criteria.
