External workload and cognitive performance of a tactical military scenario-based field exercise.

INTRODUCTION: Military personnel must manage a multitude of competing physiological and cognitive stressors while maintaining high levels of performance. Quantifying the external workload and cognitive demands of tactical military field exercises closely simulating operational environments, will provide a better understanding of stressors placed on personnel to inform evidence-based interventions. METHODS: Thirty-one soldiers completing a dismounted 48 hours tactical field exercise, participated in the study. External workload was quantified using a wrist-worn triaxial accelerometer, with cognitive function (Go-/No-Go, N-back, psychomotor vigilance task and subjective workload ratings (NASA-TLX) assessed pre-exercise, mid-exercise and postexercise. Physical activity was described using Euclidian Norm Minus One (mg), with moderate vigorous physical activity (MVPA) and sedentary light physical activity (SLPA) as ≥ or <113 mg, respectively. Changes in general cognitive performance (total accuracy-speed trade-off (ASTO) % change) and function outcome variables (overall mean reaction time, ASTO and number of correct and missed responses) were calculated for each assessment from pre-exercise, to mid-exercise and postexercise. RESULTS: For the exercise duration (50:12±02:06 hh:mm) participants spent more time completing SLPA compared with MVPA (1932±234 vs 1074±194 min; p<0.001), equating to 33% of the time spent completing MVPA. Overall cognitive performance decreased over the exercise (pre-to-post: -249). However, the largest decrement was observed pre-to-mid (-168). Perceived mental demand associated with the cognitive assessments significantly increased over the duration of the exercise (pre-: 33; mid-: 38 and post-: 51; χ2 F(2) = 26.7, p = <0.001, W=0.477) which could suggest that participants were able to attenuate a further decline in cognitive performance by investing more effort/mental resources when completing assessments. CONCLUSION: The study successfully quantified the physical activity, and subsequent impact on cognitive function, in soldiers completing a 48 hours tactical field exercise. Further research is needed to better understand how physiological stressors interact with cognitive function during military operations.

A comparison of physical performance during one- and two-person simulated casualty drags.

The ability to drag a casualty to safety is critical for numerous physically demanding occupations. This study aimed to establish whether the pulling forces during a one-person 55 kg simulated casualty drag is representative of a two-person 110 kg drag. Twenty men completed up to 12 × 20m simulated casualty drags using a drag bag (55/110 kg) on a grassed sports pitch, with completion times and forces exerted measured. Completion time for the one-person 55 and 110 kg drags were 9.56 ± 1.18s and 27.08 ± 7.71s. Completion time for the 110 kg two-person drags for forwards and backwards iterations were 8.36 ± 1.23s and 11.04 ± 1.11s. The average individual force exerted during the one-person 55 kg drag was equivalent to the average individual contribution during the two-person 110 kg drag (t(16) = 3.3780, p < 0.001); suggesting a one-person 55 kg simulated casualty drag is representative of the individual contribution to a two-person 110 kg simulated casualty drag. Individual contributions can however vary during two-person simulated casualty drags.

1.5mile run time and body mass predict 8mile loaded march performance, irrespective of sex.

OBJECTIVES: To develop a statistical model to predict 8mile Loaded March (LM) performance and quantify differences in physical characteristics for men and women British Army Personnel. DESIGN: 135 trained soldiers (87 men; 48 women) completed two sessions, seven days apart. METHODS: Session 1: Participants' stature, body mass, Fat Free Mass (FFM) [by dual-energy X-ray absorptiometry], Single Lift (SL), Water Can Carry (WCC), and 1.5mile run performance were measured. Session 2: Participants completed an 8mile LM, carrying 25kg (4miles paced and 4miles individual best effort). Sex differences were compared using independent samples t-tests and 8mile LM performance time was predicted using various multiple linear regression analysis: hierarchical forced entry multiple ordinary least squares, principal component and ordinary least products. RESULTS: A combination of 1.5mile run time and body mass were the strongest predictors of 8mile LM time (R2=0.71; SEE=4.17min; p<0.001). Including stature, FFM, sex, SL score, or WCC score did not further improve predictions (p>0.05). Compared to women, men had faster mean 1.5mile run and LM times, greater body mass and total FFM and higher SL and WCC scores (p<0.001), however some women outperformed men. CONCLUSION: 1.5mile run time and body mass predict 8mile LM performance with no further improvement gained in the model by including sex as a variable.

Energy expenditure during a single-handed transatlantic yacht race.

BACKGROUND: The popularity of sports that expose people to consecutive days of high-intensity physical activity continues to increase. The ability to adequately nourish the human body to sustain the required level of competitive performance may be a key contributor to success in such events. METHODS: The energy expenditure of a male competitor in a single-handed, transatlantic race (Transat 2004) was assessed using the doubly-labelled water technique. RESULTS: Mean total daily energy expenditure (TDEE) during the race (13 days) was 14.5 MJ/day with a peak expenditure of 18.6 MJ during the most physically demanding 24-hour period. DISCUSSION: This mean TDEE was approximately 25% lower than that reported in a previous study (14.5 vs. 19.3 MJ/day) for a 13-day leg of a fully crewed offshore race. The difference in results was probably due to the fact that in the previous study, the crew operated in "watches" (work shifts), affording each crew member greater opportunity to eat, rest and sleep. Effective planning and efficient management of resources is essential to the success of the solo sailor. However, the extent to which maintenance of energy balance underpins competitive success remains to be established. To maintain energy balance during the race, a mean daily energy intake of 14.5 MJ/day was necessary for the subject in this study. However, this mean value for energy intake would have been inadequate to match the peak energy expended during the most physically demanding 24 hours of the race.

Effect of exercise on cerebral perfusion in humans at high altitude.

The effects of submaximal and maximal exercise on cerebral perfusion were assessed using a portable, recumbent cycle ergometer in nine unacclimatized subjects ascending to 5,260 m. At 150 m, mean (SD) cerebral oxygenation (rSO2%) increased during submaximal exercise from 68.4 (SD 2.1) to 70.9 (SD 3.8) (P < 0.0001) and at maximal oxygen uptake (.VO2(max)) to 69.8 (SD 3.1) (P < 0.02). In contrast, at each of the high altitudes studied, rSO2 was reduced during submaximal exercise from 66.2 (SD 2.5) to 62.6 (SD 2.1) at 3,610 m (P < 0.0001), 63.0 (SD 2.1) to 58.9 (SD 2.1) at 4,750 m (P < 0.0001), and 62.4 (SD 3.6) to 61.2 (SD 3.9) at 5,260 m (P < 0.01), and at .VO2(max) to 61.2 (SD 3.3) at 3,610 m (P < 0.0001), to 59.4 (SD 2.6) at 4,750 m (P < 0.0001), and to 58.0 (SD 3.0) at 5,260 m (P < 0.0001). Cerebrovascular resistance tended to fall during submaximal exercise (P = not significant) and rise at .VO2(max), following the changes in arterial oxygen saturation and end-tidal CO(2). Cerebral oxygen delivery was maintained during submaximal exercise at 150 m with a nonsignificant fall at .VO2(max), but at high altitude peaked at 30% of .VO2(max) and then fell progressively at higher levels of exercise. The fall in rSO2 and oxygen delivery during exercise may limit exercise at altitude and is likely to contribute to the problems of acute mountain sickness and high-altitude cerebral edema.

A modified incremental shuttle run test for the determination of peak shuttle running speed and the prediction of maximal oxygen uptake.

The aim of this study was to determine the incidence of subject drop-out on a multi-stage shuttle run test and a modified incremental shuttle run test in which speed was increased by 0.014 m x s(-1) every 20-m shuttle to avoid the need for verbal speed cues. Analysis of the multi-stage shuttle run test with 208 elite female netball players and 381 elite male lacrosse players found that 13 (+/-3) players stopped after the first shuttle of each new level, in comparison with 5 (+/-2) players on any other shuttle. No obvious drop-out pattern was observed on the incremental shuttle run test with 273 male and 79 female undergraduate students. The mean difference between a test-retest condition (n = 20) for peak shuttle running speed (-0.03+/-0.01 m x s(-1)) and maximal heart rate (0.4+/-0.1 beats x min(-1)) on the incremental test showed no bias (P > 0.05). The 95% absolute confidence limits of agreement were+/-0.11 m x s(-1) for peak shuttle running speed and+/-5 beats min(-1) for maximal heart rate. The relationship (n = 27) between peak shuttle running speed on the incremental shuttle run test (4.22+/-0.14 m x s(-1)) and VO2max (59.0+/-1.7 ml kg(-1) x min(-1)) was r= 0.91 (P< 0.01), with a standard error of prediction of +/-2.6 ml x kg(-1) x min(-1). These results suggest verbal cues during the multi-stage shuttle run test may influence subject drop-out. The incremental shuttle run test shows no obvious drop-out patten and provides a valid estimate of VO2max.

DNA sequence analysis and restriction fragment length polymorphisms of the P1 gene of Haemophilus influenzae biogroup aegyptius associated with Brazilian purpuric fever.

Brazilian purpuric fever (BPF) is a fulminant pediatric disease caused by specific strains of Haemophilus influenzae biogroup aegyptius. A conserved epitope on the P1 protein of strains of H. influenzae biogroup aegyptius is seen on most virulent isolates. The P1 protein from a Brazilian case-clone strain of H. influenzae biogroup aegyptius was analyzed by cloning and sequencing the gene. Three major variable regions are present within the P1 gene of the BPF clone in an architecture similar to that of the previously sequenced P1 genes from H. influenzae. The DNA sequence data of the P1 gene provided information for restriction fragment length polymorphism analyses among strains of H. influenzae biogroup aegyptius. Using PCR for amplification of the P1 gene, we found that AlwI restriction of this gene allowed for a highly accurate segregation of virulent strains of H. influenzae biogroup aegyptius associated with BPF. The strong association of virulent phenotypes with specific AlwI restriction patterns of the P1 gene provides a basis for the convenient and accurate identification of strains of H. influenzae biogroup aegyptius which cause BPF.

Expression of urokinase-type plasminogen activator and plasminogen activator inhibitor in colon disease.

Surveillance colonoscopy and biopsy are inaccurate methods of predicting the likelihood of ulcerative colitis patients to develop colon carcinoma. We examined uPA and PAI-1 as potential markers for assessing these patients and those with familial polyposis who are at risk of developing colon cancer. For comparison, biopsies of normal colon and Crohn's disease were evaluated. We examined 77 colonic mucosa specimens taken from patients undergoing elective resection for benign and malignant colonic disease. uPA and PAI-1 were measured using a monoclonal antibody-based ELISA kit (American Diagnostica, Greenwich, CT) and expressed as ng/mg extract protein. Intra- and interassay controls of uPA gave CV = 3-4% and CV = 8-9%, respectively, while those for PAI-1 were 6-7% and 10-11%, respectively. The Mann-Whitney test showed that both uPA and PAI-1 expression were significantly higher in colon cancer, chronic ulcerative colitis, and Crohn's disease than in normal colon. uPA in familial polyposis samples was similar to that of normal colon, while PAI-1 was much lower than in normal colon. Neither patient age nor sex appeared to influence the expression of these potential markers in any tissue. The pattern of uPA and PAI-1 expression in normal, benign and malignant colon suggests these proteins deserve further consideration as markers for assessing colon carcinoma risk.

Stable, conserved outer membrane epitope of strains of Haemophilus influenzae biogroup aegyptius associated with Brazilian purpuric fever.

Brazilian purpuric fever is a rapidly fatal childhood disease associated with a clonal strain of Haemophilus influenzae biogroup aegyptius. We describe a conserved, surface-exposed epitope present on 95% of H. influenzae biogroup aegyptius isolates that are associated with Brazilian purpuric fever. This epitope, defined by reaction with the monoclonal antibody 8G3, is on or associated with the 48-kDa heat-modifiable P1 protein. The epitope is absent on strains of H. influenzae biogroup aegyptius that are not associated with Brazilian purpuric fever but is present on one strain of H. influenzae biotype II. None of 81 other Haemophilus strains tested reacted with 8G3. The sensitivity and specificity of the 8G3 monoclonal antibody in detecting Brazilian case-clone strains of H. influenzae biogroup aegyptius associated with Brazilian purpuric fever are 95 and 99%, respectively. Immunoelectron microscopy revealed that the epitope is surface exposed, and N-terminal amino acid sequencing of an 8G3-reactive P1 protein from a strain of H. influenzae biogroup aegyptius showed 100% correlation with the published N-terminal amino acid sequence of a P1 protein of H. influenzae type b. The virulence of the organism in an infant rat model of bacteremia was not dependent on the expression of this epitope.

Age differences in processing information from television news: the effects of bisensory augmentation.

Younger and older adults listened to segments of television news under one of three conditions: (a) Listen, in which they heard the auditory portion of the segment without its visual track; (b) Listen + Read, in which they listened to the auditory track only while reading along with a written transcript; and (c) Listen + Television, in which they heard the original televised segment complete with audio and visual track. Younger adults showed better free recall for the spoken information when it was augmented by the written transcript or video track; older adults did not show this benefit of bisensory augmentation. Subjects were also tested on a Daneman and Carpenter (1980) style measure of working memory processing. This measure accounted for virtually all age variance in memory performance in the unaugmented Listen condition. In the Listen + TV condition, however, there was a substantial proportion of age variance in performance which could not be accounted for in terms of working memory processing. Results are discussed in terms of the varying involvement of working memory processing in age differences as a function of input modality.

Progesterone-induced sequential inhibition of copulatory behavior in hysterectomized rats: relationship to neural cytoplasmic progestin receptors.

The inhibitory effects of progesterone on the copulatory behavior and on neural cytoplasmic progestin receptors were examined in ovariectomized (DV) and ovariectomized-hysterectomized (OH) rats. Ovariectomized and OH rats were given 2.0 micrograms of estradiol benzoate (EB) followed 24 hr later by 0.1, 0.5, 0.1 or 2.0 mg of progesterone (P) and were tested for lordosis 6 hr later (30 hr). Twenty four hr after the first P treatment, all animals received 0.5 mg of P and were tested again (54 hr). The initial doses of 1.0 and 2.0 mg of P significantly reduced lordosis quotients in response to the subsequent P treatment in OV animals but only the 2.0 mg dose of P effectively suppressed lordosis in OH animals. In order to determine whether the priming dose of EB influences the inhibitory effects of progesterone, OV and OH rats were injected with 1.0 microgram of EB followed by 1.0 mg of P, or 6.0 micrograms of EB followed by 2.0 mg of P and were tested for receptivity under the same schedule. Treatment with 1.0 microgram of EB permitted, and 6.0 micrograms of EB prevented sequential inhibition of sexual behavior by progesterone in both OV and OH rats. Hypothalamic cytoplasmic progestin [( 3H]R5020) receptors were then measured 48 hr after EB injection in OV or OH rats given the same treatments with EB and P. Hypothalamic progestin receptors were significantly lower in OV animals given 2.0 micrograms of EB followed by 1.0 or 2.0 mg of P than oil-treated controls, but only the 2.0 mg dose of P significantly reduced receptors in OH rats.(ABSTRACT TRUNCATED AT 250 WORDS)