Intense Military Training Research Articles

Relation between cardiac vagal tone and performance in male military personnel exposed to high stress: Three prospective studies

Vagal tone has been proposed both as an index of emotion regulation and cognitive ability. To assess the relation between vagal tone and emotion regulation and cognitive ability, the present research prospectively measured vagal tone (measured either as high-frequency spectral power or respiratory sinus arrhythmia) in healthy participants exposed to high stress. The participants were active duty military personnel (men) enrolled in high intensity military training: Survival School (Experiments 1 and 3) and Combat Diver Qualification Course (Experiment 2). We consistently observed a significant relationship between low vagal tone and superior performance. The data suggest that vagal suppression is associated with enhanced performance under conditions of high stress and that this enhanced performance may be related to emotion regulation and cognitive functioning.

Hormonal Changes Following Intense Military Training

Hormonal Changes Following Intense Military Training

Immune and Hormonal Changes following Intense Military Training

This study was designed to determine whether the immune and hormonal systems were affected by a 5-day military course following 3 weeks of combat training in a population of 26 male soldiers (mean age, 21 +/- 2 years). The combination of continuous heavy physical activity and sleep deprivation led to energy deficiency. At the beginning of the training program and immediately after the combat course, saliva samples were assayed for secretory immunoglobulin A and plasma samples were assayed for interleukin-6, dehydroepiandrosterone sulfate, prolactin, catecholamines, glucocorticoids, and testosterone. Secretory immunoglobulin A was lower and circulating interleukin-6 was increased by the end of the course, which was attributed to sympathoadrenergic stimulation. Dehydroepiandrosterone sulfate, prolactin, and testosterone levels fell significantly. These results suggest that prolonged and repeated exercise such as that encountered in a military training program induces immune impairment via a decrease in mucosal immunity and a release of interleukin-6 into the circulation. The impaired secretion of dehydroepiandrosterone sulfate and prolactin, two immunomodulatory hormones, was thought to be a response to the chronic stressors. Lowered testosterone reflects a general decrease in steroid synthesis as a consequence of the physical and psychological strain.

Halting a pneumococcal pneumonia outbreak among United States Marine Corps trainees

Background Streptococcus pneumoniae is the leading cause of bacterial pneumonia in all age groups. Identifying outbreaks of pneumococcal disease and key risk factors may lead to improvements in vaccination and prevention strategies for high-risk groups. A significant outbreak of S. pneumoniae pneumonia that occurred among Marine recruits is reported here. Methods An outbreak was investigated using standard microbiologic procedures and epidemiologic evaluation to define the extent of the outbreak, determine the microbiologic causative agent(s), identify risk factors for the development of disease, and institute preventive measures against further cases of pneumonia among recruits. Results Fifty-two cases of radiographically confirmed pneumonia occurred among 3367 Marine recruits over a 2-week period in November 2000. Twenty-five of these cases occurred in a single company of 481 men, with an attack rate of 5.2%. Twelve of the 25 cases were caused by S. pneumoniae, serotypes 4 and 9v. The outbreak rapidly ended following isolation of cases, prophylaxis with oral azithromycin, and administration of the 23-valent pneumococcal vaccine. Conclusions This outbreak of pneumococcal disease occurred in the setting of intense military training and a crowded environment. The use of the pneumococcal vaccine year-round in military trainees and other high-risk populations to reduce pneumococcal disease should be considered.

INFLUENCE OF MILITARY ACTIVITIES ON RAPTOR ABUNDANCE AND BEHAVIOR

Abstract We investigated the influence of military training on the abundance and behavior of raptors at a military training area in the Snake River Birds of Prey National Conservation Area in Idaho during the breeding seasons of 1991–1994. Raptor counts on military training ranges did not differ when we compared all training days to all non-training days. However, during one period of intensive military training in one breeding season, raptor counts were lower during training than on non-training days. During training, Northern Harriers (Circus cyaneus) did not alter their behavior on training days. In years when prey numbers were low, falcons, hawks, and eagles perched and flew at low levels less often and flew at higher altitudes more often during training than they did when training did not occur. We observed fewer prey capture attempts on ranges on days with training than on days without training. Specific types of military training activity affected counts of raptors on ranges. The lowest raptor coun...

Plasma neuropeptide-Y concentrations in humans exposed to military survival training

Background: Neuropeptide-Y (NPY) is present in extensive neuronal systems of the brain and is present in high concentrations in cell bodies and terminals in the amygdala. Preclinical studies have shown that injections of NPY into the central nucleus of the amygdala function as a central anxiolytic and buffer against the effects of stress. The objective of this study was to assess plasma NPY immunoreactivity in healthy soldiers participating in high intensity military training at the U.S. Army survival school. The Army survival school provides a means of observing individuals under high levels of physical, environmental, and psychological stress, and consequently is considered a reasonable analogue to stress incurred as a result of war or other catastrophic experiences. Methods: Plasma levels of NPY were assessed at baseline (prior to initiation of training), and 24 hours after the conclusion of survival training in 49 subjects, and at baseline and during the Prisoner of War (P.O.W.) experience (immediately after exposure to a military interrogation) in 21 additional subjects. Results: Plasma NPY levels were significantly increased compared to baseline following interrogations and were significantly higher in Special Forces soldiers, compared to non-Special Forces soldiers. NPY elicited by interrogation stress was significantly correlated to the subjects’ behavior during interrogations and tended to be negatively correlated to symptoms of reported dissociation. Twenty-four hours after the conclusion of survival training, NPY had returned to baseline in Special Forces soldiers, but remained significantly lower than baseline values in non–Special Forces soldiers. NPY was positively correlated with both cortisol and behavioral performance under stress. NPY was negatively related to psychological symptoms of dissociation. Conclusions: These results provide evidence that uncontrollable stress significantly increases plasma NPY in humans, and when extended, produces a significant depletion of plasma NPY. Stress-induced alterations of plasma NPY were significantly different in Special Forces soldiers compared to non–Special Forces soldiers. These data support the idea that NPY may be involved in the enhanced stress resilience seen in humans.

CAUSE-SPECIFIC MORTALITY OF WHITE-TAILED DEER AS INFLUENCED BY MILITARY TRAINING ACTIVITIES IN SOUTHWESTERN OKLAHOMA

Radio-telemetry was used to monitor movements and mortality of 56 white-tailed deer (Odocoileus virginianus) in response to intensive military training activities on West Range (18,000 ha), Fort Sill Military Reservation, Oklahoma. Cause-specific mortality was determined for 22 radio-collared deer, including adults (greater than or equal to 2.0-yr-old), yearlings (0.6-1.9-yr-old), and fawns (less than or equal to 75-day-old age group) from 1987 to 1989. Winter home ranges were largely confined to a 14,411 ha impact area centrally located on West Range. The mean annual mortality rate was 0.50 for adults and yearlings combined. Fifty percent of all adult and yearling mortality was attributed to military training activities, 28% to hunting, 16% to collisions with automobiles, and 6% to unknown causes. The mean monthly mortality rate was 0.61 for neonatal fawns and predation accounted for three of four mortalities. All captured deer in the greater than or equal to 2.6-yr-old, 82% in the 1.6-yr-old, 10% in the 0.6-yr-old, and all deer in the less than 7-day-old age groups were seropositive for bluetongue virus (BTV). Our study strongly suggests that the consequences of military training activities should be considered in the management of white-tailed deer herds on military installations.

Changes in lipoprotein profiles during intense military training.

The effects of intense military training on lipoprotein concentrations were monitored in a group of 44 Navy trainees. Dietary intakes and lipoprotein profiles were obtained before and after 5 weeks of physical conditioning and after 5 days of continuous, extremely intense physical and psychological stress. Body weight did not change significantly and dietary intakes were consistently high in saturated fat and cholesterol. After physical conditioning, serum total cholesterol and triglyceride concentrations were unchanged, while high-density lipoprotein (HDL) concentrations increased 31% (p less than 0.05). After 5 days of severe stress, total cholesterol and low-density lipoprotein concentrations decreased 17.2% and 30%, respectively (p less than 0.05), whereas HDL concentrations increased 12.1%. These data indicate that marked changes in lipoprotein profiles occur, not only with long-term physical conditioning, but also with strenuous training that lasts several days, despite high energy, fat, and cholesterol intakes.

Orthopedic history and examination in the etiology of overuse injuries

Overuse injuries, and stress fractures in particular, afflict many runners and military recruits. This investigation sought to identify pretraining factors which may predispose to overuse injuries. Orthopedic and running history questionnaires and an orthopedic examination were administered to 505 trainees entering an intensive military training school. A novel method for evaluating ankle dorsiflexion was developed, and alignment measures, in units of centimeters rather than degrees, were obtained. Over 10% of the trainees were removed from the school for overuse-related injuries, and over half of these were tibial stress fractures. The incidence of clinically diagnosed stress fractures was 6.3%. No single orthopedic history question or combination of questions could discriminate between trainees who did or did not subsequently incur overuse injuries. Results from the running history indicated that those running 25 or more miles.wk-1 (mpw) had a significantly (P less than 0.027) lower incidence of stress fractures (3.0%) than those running 4 or fewer mpw over the previous year (11.5%). The orthopedic examination did not identify any predisposing alignment characteristics, perhaps due to the low incidence of overuse injuries. Population means are presented for future use in comparative studies.

Elections and U.S. Intervention in Nicaragua

power of the people will never be defeated, neither with bullets nor with ballots. Thus declared Sandinista Comandante Daniel Ortega on December 4, 1983, in firing the opening shots of the Nicaraguan electoral process. The then coordinator of the National Reconstruction Government Junta announced to the nation during a special session of the Council of State (parliament) that the process would officially open on January 31, 1984, and culminate with general elections in early 1985. Only days before, the All the Arms to the People campaign came to a close: The last air-raid shelters had been dug, tens of thousands of new militia members completed intensive military training courses, the peasants in the war zones were fully armed, and the entire population had been organized into civil defense units. Nicaragua was emerging from a military emergency that brought the country to the most tense moment it had yet experienced since the triumph of the revolution on July 19, 1979. The massive defense preparations were brought to a high pitch following the U.S. invasion of Grenada. According to all forecasts, Nicaragua was next on Washington's list. However, a swift Sandinista diplomatic offensive internationally, combined with political considerations in Washington, led the Reagan administration to shelve temporarily the Nicaraguan invasion plan in late 1983. Unable to prevent the Sandinista triumph through direct intervention, the objective of U.S. policy toward Nicaragua since 1979 has been to undermine consolidation of the revolutionary process. The Carter administration attempted to divert the course of the revolution through

Weight and skinfold thickness changes during a physical training course

The effect of an intensive physical training program on body weight and skinfold thickness was compared in subjects who had initially small (group S), medium (group M) and large (group L) skinfold thickness representing mostly thin, normal and obese recruits, respectively. Weight and skinfold thickness at three sites (triceps, subscapula and abdomen) were measured at the beginning and end of a 6 week intensive military training program. Subjects were on an ad-lib diet. Seventy-one percent of the subjects in group S increased their body weight and 60% increased the sum of their skinfold thickness (SSFT) at the three sites during the training period. These increases were significant at P less than 0.001 and P less than 0.01 for weight and SSFT respectively. In groups M and L the trends for changes in SSFT were in the opposite direction, with 68% of the former and 98% of the latter showing decreases in SSFT. The mean decreases were significant at P less than 0.02 and P less than 0.001 for groups M and L respectively. While the subjects in group L lost weight significantly (P less than 0.001), those in group M reduced their weight only slightly. Our data indicate that changes in body fat, indicated by changes in SSFT, during several weeks of physical activity are not unidirectional and are related to the initial skinfold thickness.