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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two types of experiments concerning estimated magnitude of self-motion during exposure to linear oscillation on a parallel swing are described in this paper. Experiment I examined changes in magnitude estimation as a function of variation of the subject's head orientation, and Experiments II a, II b, and II c assessed changes in magnitude estimation performance following exposure to sustained, "intense" linear oscillation (fatigue-inducing stimulation). The subjects' performance was summarized employing Stevens' power law (R = k . Sn, where R is perceived self-motion magnitude, k is a constant, S is amplitude of linear oscillation, and n is an exponent). The results of Experiment I indicated that the exponents, n, for the magnitude estimation functions varied with head orientation and were greatest when the head was oriented 135 degrees off the vertical. In Experiments II a-c, the magnitude estimation function exponents were increased following fatigue. Both types of experiments suggest ways in which the vestibular system's contribution to a spatial orientation perceptual system may vary. This variability may be a contributing factor to the development of pilot/astronaut disorientation and may also be implicated in the occurrence of motion sickness.
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PMID:Self-motion magnitude estimation during linear oscillation: changes with head orientation and following fatigue. 4 23

Three sea going vessels steamed side by side through slight seas off the coast of Oahu, Hi. A 4-h octagon was transmitted twice each day for three consecutive days while motion sickness symptomatology was recorded from 18 enlisted men who alternated among the vessels. Dramatic differences in illness severity were obtained whether comparisons were made using objective evidence of vomiting episodes or subjective reporting of symptoms on questionnaires. Reliability of this scoring method was excellent (r = .95). In addition to face and construct validity, evidence is presented of the predictive validity of the scoring method in a separate octagonal steaming experiment using a 95 ft Coast Guard patrol boat in an equivalent experimental paradigm. This study showed significant covariance between the magnitude of motion sickness symptomatology and the encounter direction of the vessel to the primary swell (p less than 0.01). Additionally, significant correlations were found between sickness severity and test subject concentration, fatigue, urine production, and urine specific gravity. The majority of these relationships would not have been disclosed had only the dichotomous criterion of vomit/nonvomit been employed in assessing motionsickness severity. Implications of these data as design criteria for marine vehicles are discussed.
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PMID:Susceptibility to seasickness: influence of hull design and steaming direction. 51 49

The purpose of the present study was to investigate the effects on driving ability of the new analgesic ethyl-N-(2-amino-6-(4-fluor-phenylmethylamino) pyridin-3-yl) carbamate (flupirtine, D 9998) in comparison with pentazocine and placebo. Flupirtine was tested in a double blind cross-over experiment in 12 healthy volunteers using 7 different tests which are known to correspond to the most important aspects of driving ability. Subjects were given 3 consecutive doses of flupirtine of 100 mg each and tested following the first and third administration. The comparison drug pentazocine and placebo were administered in the same dosage regimen (a single dose of pentazocine amounting to 50 mg). Significant differences between flupirtine and placebo could not be detected. Following single dosage of pentazocine subjects more often reported a general feeling of discomfort, including nausea, dizziness and motion sickness, than was the case after administration of flupirtine. While single administration of pentazocine did not produce any significant differences from placebo, multiple administration resulted in both objective and subjective fatigue symptoms. It was concluded that flupirtine, in contrast to pentazocine, did not produce any impairment in driving ability in healthy volunteers.
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PMID:[The effect of the analgesic flupirtine on automobile driving]. 403 55

Coca appears to be a useful treatment for various gastrointestinal ailments, motion sickness, and laryngeal fatigue. It can be an adjunct in programs of weight reduction and physical fitness and may be a fast-acting antidepressant. It is of value in treating dependence on stronger stimulants. Coca regulates carbohydrate metabolism in a unique way and may provide a new therapeutic approach to hypoglycemia and diabetes mellitus. With low-dose, chronic administration it appears to normalize body functions. In leaf form coca does not produce toxicity or dependence. Coca can be administered as a chewing gum or lozenge containing a whole extract of the leaf, including alkaloids, natural flavors, and nutrients.
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PMID:The therapeutic value of coca in contemporary medicine. 611 6

Jet lag. Present day aircraft operating round northern and southern latitudes cross time zones at almost the same rate as the earth rotates, and it is these rapid transmeridian transitions that lead to the syndrome commonly referred to as jet lag. On arrival at their destination, individuals find themselves out of synchrony with the social and time cues of their new environment and, until they adapt, may experience symptoms such as malaise, gastrointestinal disturbance, loss of appetite, tiredness during the day and poor sleep. The severity and exact nature of the problems vary with the direction of travel and the number of time zones crossed, and some people react more unfavourably to intercontinental travel than others. Clearly, with increasing numbers of passengers undertaking such journeys, there is considerable interest in strategies to reduce the immediate effects of jet lag or to facilitate acclimatisation. Motion sickness is a generic term which embraces seasickness, airsickness, carsickness, space sickness etc, names that identify the provocative environment or vehicle. It is a normal reaction of humans to exposure to certain motion stimuli that occur during passive transportation.
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PMID:Jet lag and motion sickness. 833 93

Promethazine hydrochloride, Phenergan, is a phenothiazine derivative with antihistaminic (H1), sedative, antiemetic, anticholinergic, and antimotion sickness properties. These properties have made promethazine a candidate for use in environments such as microgravity, which provoke emesis and motion sickness. Recently, we evaluated carotid baroreceptor-cardiac reflex responses during two Space Shuttle missions 18 to 20 hr after the 50 mg intramuscular administration of promethazine. Because the effects of promethazine on autonomic cardiovascular mechanisms in general and baroreflex function in particular were not known, we were unable to exclude a possible influence of promethazine on our results. Our purpose was to determine the ground-based effects of promethazine on autonomic cardiovascular control. Because of promethazine's antihistaminic and anticholinergic properties, we expected that a 50-mg intramuscular injection of promethazine would affect sympathetically and vagally mediated cardiovascular mechanisms. Eight healthy young subjects, five men and three women, were studied at rest in recumbency. All reported drowsiness as a result of the promethazine injection; most also reported nervous excitation, dry mouth, and fatigue. Three subjects had significant reactions: two reported excessive anxiety and one reported dizziness. Measurements were performed immediately prior to injection and 3.1 +/- 0.1 and 19.5 +/- 0.4 hr postinjection. We found no significant effect of promethazine on resting mean R-R interval, arterial pressure, R-R interval power spectra, carotid baroreflex function, and venous plasma catecholamine levels.
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PMID:Promethazine affects autonomic cardiovascular mechanisms minimally. 926 49

To study the main predictors of childhood preschool headache, 1443 families expecting their first child were followed from the onset of pregnancy to the child's sixth year of life. Subject selection was based on stratified randomized cluster sampling. Of the children, 14.9% (144) suffered from headache disturbing daily activities at the age of 6 years. The mother's assessment of the infant's poor health (OR 2.5, 95% CI 1.1 to 5.8) and feeding problems (OR 1.9, 95% CI 1.1 to 3.2) at the age of 9 months predicted later occurrence of headache. At 3 years, depression and sleeping difficulties (according to Achenbach's psychological test) and recurrent difficulties in falling asleep (OR 3.2, 95% CI 1.5 to 7.2) were strong predictors. Headache in other family members (OR 3.5, 95% CI 2.0 to 5.9), especially in the mother (OR 1.7, 95% CI 1.2 to 2.4), predicted preschool headache in a child. At the age of 5 years, travel sickness (OR 2.8, 95% CI 1.5 to 5.1), nocturnal enuresis (OR 1.8, 95% CI 1.1 to 3.0), and the presence of long-term disease (OR 1.8, 95% CI 1.1 to 3.0) were strong predictors of later headache. At the same age, concentration difficulties (OR 2.3, 95% CI 1.3 to 4.2), behavioral problems (OR 2.7, 95% CI 1.1 to 6.4), unusual tiredness (OR 3.8, 95% CI 1.0 to 13.5), and, conversely, high sociability (OR 1.5, 95% CI 1.0 to 2.2) predicted headache. The three last-mentioned psychological factors seemed to be associated with concentration difficulties at the age of 5, which was found to be the strongest predictor. The parents of child headache sufferers often became aware of the child's problems long before the emergence of headache.
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PMID:Factors of early life as predictors of headache in children at school entry. 950 99

The present paper provides a review of research and theories concerning the question of how and why working in a moving environment may affect performance. It is argued that performance decrements can be expected to occur as a result of general factors or as a result of specific impairments of particular human skills. General effects happen when environmental motion, simulated or real, reduces motivation (due to motion sickness), increases fatigue (due to increased energy requirements), or creates balance problems. Specific effects of moving environments on task performance may only be expected through biomechanical influences on particular skills such as perception (interference with oculomotor control) or motor skills (such as manual tracking). There is no evidence for direct effects of motion on performance in purely cognitive tasks.
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PMID:Working in a moving environment. 985 42

Increased speeds of trains can be achieved by using tilting trains that decrease the lateral acceleration experienced by passengers on curves, thereby allowing trains to run typically 25-30% faster on existing curved track and maintaining good ride comfort. Unfortunately, motion sickness in tilting trains is a major problem for some passengers. To investigate the incidence of motion sickness and the extent to which different tilt compensation strategies influence its occurrence, tests were conducted with a tilting train on a track with a large number of curves. Eighty healthy volunteers were studied, selected partly for their susceptibility. Three different cars were evaluated during 3 test days, with each test ride lasting about 3 h. On four occasions per test ride, the subjects answered a questionnaire concerning activities during the ride, ride comfort, ability to work and read, vegetative symptoms, fatigue, sleepiness, nausea and well-being. Subjects estimation of average ride comfort and ability to work and read was good in all conditions. However, 10% of the test subjects reported various symptoms of motion sickness (SMS). A 55% degree of tilt compensation of the lateral acceleration instead of the normal 70% reduced the symptoms of motion sickness incidence (SMSI) by 25-40%. SMSI correlated poorly with motion doses, which integrates vertical or lateral acceleration but correlated well with roll acceleration motion dose (r2 = 0.43, p < 0.001). For women, riding backward (p < 0.001) minimized SMSI, but men were insensitive to direction. Future railway design will have to optimize tilt systems by both minimizing motion sickness and avoiding excessive lateral acceleration or jerk.
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PMID:Influence of different conditions for tilt compensation on symptoms of motion sickness in tilting trains. 1005 84

To study the potential aftereffects of virtual environments (VE), tests of visually guided behavior and felt limb position (pointing with eyes open and closed) along with self-reports of motion sickness-like discomfort were administered before and after 30 min exposure of 34 subjects. When post- discomfort was compared to a pre-baseline, the participants reported more sickness afterward (p < 0.03). The change in felt limb position resulted in subjects pointing higher (p < 0.038) and slightly to the left, although the latter difference was not statistically significant (p = 0.08). When findings from a second study using a different VE system were compared, they essentially replicated the results of the first study with higher sickness afterward (p < 0.001) and post- pointing errors were also up (p < 0.001) and to the left (p < 0.001). While alternative explanations (e.g. learning, fatigue, boredom, habituation, etc.) of these outcomes cannot be ruled out, the consistency of the post- effects on felt limb position changes in the two VE implies that these recalibrations may linger once interaction with the VE has concluded, rendering users potentially physiologically maladapted for the real world when they return. This suggests there may be safety concerns following VE exposures until pre-exposure functioning has been regained. The results of this study emphasize the need for developing and using objective measures of post-VE exposure aftereffects in order to systematically determine under what conditions these effects may occur.
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PMID:Motion sickness and proprioceptive aftereffects following virtual environment exposure. 1009 14


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