Psychological stress during exercise: cardiorespiratory and hormonal responses.

The purpose of this study was to examine the cardiorespiratory (CR) and stress hormone responses to a combined physical and mental stress. Eight participants (VO2(max) = 41.24 +/- 6.20 ml kg(-1) min(-1)) completed two experimental conditions, a treatment condition including a 37 min ride at 60% of VO2(max) with participants responding to a computerized mental challenge dual stress condition (DSC) and a control condition of the same duration and intensity without the mental challenge exercise alone condition (EAC). Significant interactions across time were found for CR responses, with heart rate, ventilation, and respiration rate demonstrating higher increases in the DSC. Additionally, norepinephrine was significantly greater in the DSC at the end of the combined challenge. Furthermore, cortisol area-under-the-curve (AUC) was also significantly elevated during the DSC. These results demonstrate that a mental challenge during exercise can exacerbate the stress response, including the release of hormones that have been linked to negative health consequences (cardiovascular, metabolic, autoimmune illnesses).

Cardiorespiratory responses of Hi Fit and Low Fit subjects to mental challenge during exercise.

The influence of psychological states on physiological responses during exercise is of considerable importance to individuals for which the efficiency of energy production is critical to occupational performance. Numerous studies have shown that aerobic fitness is associated with enhanced cardiovascular efficiency at rest and that responses to mental stress demonstrate evidence of increased sensitivity (relative increase in HR response) and enhanced efficiency (a decrease in absolute HR). However, the effect of aerobic fitness and its impact on cardiorespiratory (CR) responses to psychological stress during exercise has not been investigated. Therefore, the purpose of this study was three-fold; (1) to examine during exercise, anxiety, effort sense, and CR responses to a mental challenge, (2) to examine anxiety and heart rate (HR) responses from rest to exercise with mental challenge between below average fitness (Low Fit) and well-above average fitness (Hi Fit) individuals (exercising at similar relative intensities), and (3) to examine anxiety, effort sense, and CR responses of Low Fit and Hi Fit individuals to a mental challenge during exercise at a similar relative intensity. Twelve Low Fit and eleven Hi Fit subjects participated in two, 32-minute cycle ergometer rides at 65 % of VO2max. In the mental challenge condition (MCC), subjects rode while participating in mentally challenging tasks (Stroop Color-Word task and mental arithmetic) from min 6 to min 14 of the protocol. In the no mental challenge condition (NMCC), subjects exercised at the same intensity and duration without a stressor. Subjects were counter-balanced between fitness levels and condition. HR, VE, VE/VO2, RR, VO2, RER, effort sense (RPE), and state anxiety (SAI) were assessed at 5, 14, 24, and 30 min. SAI was also assessed at - 5 min before exercise and after 15 min of recovery. In addition, the NASA task load index (NTLX) was used to assess perceived overall workload. SAI increased significantly at 14 min in the MCC. NTLX scores indicated that the MCC was perceived as a greater overall workload. Furthermore, HR, VE, VE/VO2, and RR were significantly elevated during the mental challenge condition at 14 min. The Hi Fit subjects tended to respond to the dual stress of exercise and mental challenge with a relative increase in HR, while absolute HR was similar in both groups. An examination of fitness group differences revealed that SAI and NTLX were similar for Low Fit and Hi Fit subjects when exercising in the MCC, although, Hi Fit subjects demonstrated lower HR responses from 6 min to 14 min. VE, VE/VO2, and RR were similar for Low Fit and Hi Fit subjects. These results suggest that psychological stress during physical activity can exacerbate cardiorespiratory responses and suggests that factors that impact CR adjustment to mental challenge from resting baseline may differ from the factors that impact CR adjustment to mental challenge during exercise. Finally, fitness level attenuates HR and may attenuate additional cardiorespiratory responses while participating in a dual stress condition, of exercise and mental challenge.

Canine visceral leishmaniasis in Sicily.

The Sicilian province of Catania is an active foci for human visceral leishmaniasis (VL) in the Mediterranean area. Approximately 10 to 15 cases of VL are diagnosed via hospital admissions each year in this community. Recently, an increase in VL case reporting by Sicilian physicians was noted, with 38 and 37 VL cases in 1996 and 1997, respectively. Before 1995, there were no reported VL cases among U.S. military personnel or their family members living in Sicily. However, since 1996, there have been four cases referred to Walter Reed Army Medical Center for diagnosis and treatment, all involving the children of personnel assigned to Naval Air Station Sigonella. Exposure histories for all infected individuals excluded exposure to Leishmania parasites outside of Sicily. All patients lived in areas where vectoring sandflies are present. All had dogs as family pets. To evaluate the level of infection among dogs owned by Navy personnel and their families, U.S. Navy Environmental and Preventive Medicine Unit 7, in a collaborative study with the U.S. Army Veterinary Clinic, Naval Air Station Sigonella, and the Walter Reed Army Institute of Research, performed clinical evaluation and serological testing of 50 dogs residing with U.S. personnel assigned to Naval Air Station Sigonella. The data indicate a high exposure rate to Leishmania (60% of the animals tested had elevated immunoglobulin M antibody levels) in the study population, suggesting that they were infected with Leishmania infantum. Distribution of seropositive dogs by sex was equal. Most of the dogs studied appeared to be in good health. However, inapparent infection of dogs, seen by Italian veterinarians, has been observed throughout all areas of Catania. Sandflies responsible for vectoring L. infantum were trapped in the same locations as the dogs sampled in this study. The level of subclinical infection was 75% among seropositive dogs. The overall level of canine infection observed was higher than expected. This study demonstrates an increased risk to military working dogs and companion dogs of U.S. personnel for infection with L. infantum during a 2- to 3-year tour in Sicily.

Enterotoxigenic Escherichia coli diarrhea in children less than five years of age in central Java.

A community-based prospective study was performed from December 1993 through March 31, 1994 in Indonesia in children less than five years of age. Enterotoxigenic Escherichia coli (ETEC) was identified in diarrheic stool by colony hybridization assay, using toxin probes, and this bacterium was isolated from 19% of 340 episodes of diarrhea. Sixty-one percent of ETEC produced heat-labile toxin (LT) only, 325 LT and heat-stable toxin (ST), and 75 ST only. The age-specific incidence rates of diarrhea among children 0-1 and 2-3 years of age were 77% and 61%, respectively, during the study period; ETEC was isolated from 26% of children 0-1 years of age versus 53% for children 2-3 years of age. As many as seven episodes of diarrhea were repeatedly experienced by a single child during the four-month study period; however, only two children had more than one episode of known ETEC-associated diarrheal disease during the period of observation.

Epidemiology of enterotoxigenic Escherichia coli-associated diarrheal disease occurring on board U.S. Navy ships visiting Asian ports.

Diarrhea represents a major health threat to U.S. military forces overseas, especially in developing countries. For military units, this illness can adversely affect combat readiness. USNAMRU-2 investigators joined several U.S. Navy ships to assess the epidemiology of diarrhea illness as a result of port visits to Asia. The primary goals were to enumerate episodes of diarrhea associated with port visits, identify epidemiologic factors leading to illness, and characterize the etiologic agents. Enterotoxigenic Escherichia coli (ETEC) was the most common organism isolated from patients presenting with diarrhea and represented 22% of diarrhea cases. Vomiting and abdominal pain differentiated ETEC from other causes of diarrhea.

Screening for Chlamydia trachomatis by the direct fluorescent antibody test in female Navy recruits.

Female Navy recruits at risk for sexually transmitted diseases were screened for Chlamydia trachomatis. The screening method was the direct fluorescent antibody (FA) test. The patients represented all areas of the U.S. Average age was 20.4 years. Patients listed past gynecological infections and current symptoms. The clinical findings of the provider at examination and the results of the direct FA test were correlated. There does not appear to be a reliable office method to predict which patients will have positive FA for Chlamydia. The direct FA test is a good tool to predict infection and institute treatment in high-risk patients.