The shock attenuation characteristics of four different insoles when worn in a military boot during running and marching.

A study was undertaken to determine if placing shock absorbing insoles in the boots of Royal Marine recruits would attenuate the peak pressure at the foot-boot interface, when marching at 4.8 kph carrying a 32 kg (70 lb) Bergen and running at 12.8 kph in loose order plus webbing weighing 10 kg (22 lb). Four types of insoles were assessed: viscoelastic polymetric insole (Cambion(R)) polymetric foam insole (PPT(R)) Saran insole (military issue) and Sorbothane(R). There was a fifth control condition in which no insoles were used. Pressure measurements during heel strike and forefoot loading were taken using Paratec equipment with pressure measuring insoles placed in the boots. Data were obtained from eleven subjects and indicated that all the insoles significantly (P<0.05) attenuated the peak pressures generated during heel strike and forefoot loading. The performance of the four insoles in terms of peak pressure attenuation ranked in order with the best first were: Sorbothane Cambion PPT Saran. The Sorbothane insole was substantially and significantly (P<0.05) better than the other insoles in terms of attenuating peak pressures during heel strike. During running, mean peak pressure at heel strike was 494 kPa in the control condition, this was reduced to 377 kPa when wearing Sorbothane insoles (a reduction of 27%). When marching the Sorbothane insoles reduced the mean peak pressure at heel strike from 395 kPa (control) to 303 kPa (23% reduction). During forefoot loading the peak pressure attenuation of all four insoles was similar, although on average the Sorbothane insole performed slightly better than the others and was significantly different (P<0. 05) to the Cambion insole. Mean peak forefoot loading pressure in the control condition when running was 413 kPa, with the Sorbothane insole it was 367 kPa, during marching the respective mean peak pressures were 397 and 323 kPa. It is concluded that of the four types of insoles assessed the Sorbothane insoles attenuated the greatest amounts of the peak pressure generated at heel strike and during forefoot loading when running and marching wearing military boots.

Cognitive performance over 7 days in a distressed submarine.

BACKGROUND: This article contains the results from a psychological assessment of submariners undergoing a survival trial simulating conditions in a disabled submarine. The aim was to determine whether the environmental conditions and rations in a submarine escape compartment had any detrimental effects on cognitive performance. METHODS: The study was conducted in an environmental chamber in which the temperature fell from 22 degrees C to 4.4 degrees C over 2 d and then remained at 4.4 C for 5 d. Of the 11 subjects who were given daily rations of 100 g of barley sugar and 568 ml of water (none on day 1), only 4 remained for the full trial duration. Subjects were administered 2 psychometric tests (choice reaction time and short term memory) on hand held computers. RESULTS: Results showed that subjects did not exhibit any significant performance decrements during the experimental phase of the trial. However anecdotal evidence from observations and subjects' self reports suggest that sustained performance was impaired.

Cerebral perfusion and psychometric testing after exposure to high altitude in the mountains.

Exposure to hypobaric hypoxia is known to cause reductions in mental performance and decision-making and it has been reported that these effects are not fully reversed following descent from altitude. Eight climbers had cerebral perfusion scans performed and undertook a battery of psychometric tests prior to, and upon return from, an expedition to climb the eleventh highest mountain in the world, Gasherbrum 1. No decrements were found in either their performance on the psychometric tests nor to their cerebral perfusion following the expedition. Two subjects had significant cerebral perfusion abnormalities prior to the expedition, which had improved immediately following their return from the expedition. Repeat scans four months later showed the lesion of one of the subjects had returned and there were indications that the lesion in the other subject was beginning to return. These findings are in contrast to previous studies which have suggested that altitude exposure leads to permanent reductions in brain function, this could be because in those studies factors other than hypobaric hypoxia per se lead to the reductions in brain function.

The effects of warming by active and passive means on the subsequent responses to cold water immersion.

Two experiments were undertaken to investigate the effects of warming the body upon the responses during a subsequent cold water immersion (CWI). In both experiments the subjects, wearing swimming costumes, undertook two 45-min CWIs in water at 15 degrees C. In experiment 1, 12 subjects exercised on a cycle ergometer until their rectal temperatures (Tre) rose by an average of 0.73 degree C. They were then immediately immersed in the cold water. Before their other CWI they rested seated on a cycle ergometer (control condition). In experiment 2, 16 different subjects were immersed in a hot bath (40 degrees C) until their Tre rose by an average of 0.9 degrees; they were then immediately immersed in the cold water. Before their other CWI they were immersed in thermoneutral water (35 degrees C; control condition). Heart rate in both experiments and respiratory frequency in experiment 1 were significantly (P < 0.05) higher during the first 30 s of CWI following active warming. In experiment 1, the rate of fall of Tre during the final 15 min of CWI was significantly (P < 0.01) faster when CWI followed active warming (2.46 degrees C.h-1) compared with the control condition (1.68 degrees C.h-1). However, this rate was observed when absolute Tre was still above that seen in the control CWIs. It is possible, therefore, that if longer CWIs had been undertaken, the two temperature curves may have converged and thereafter fallen at similar rates; this was the case with the aural temperature (Tau) seen in experiment 1 and the Tau and Tre in experiment 2. It is concluded that pre-warming is neither beneficial nor detrimental to survival prospects during a subsequent CWI.