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

The vital first phase of the overall materials study to protract the life of the total joint replacements is the identification of the fracture toughness and fatigue properties of bone cements. Information gained from fatigue testing, performed in a manner which simmulates in vivo conditions, and fracture toughness, which is a measure of the propensity of a crack to propagate, is the first step towards the prediction of the life of the total joint replacement. This study is concerned with the fracture toughness of Zimmer and Simplex-P cold-curing bone cements. Following cement fabrication conditions which closely approximate clinical procedures, fracture toughness testing was conducted on cement specimens which were immersed in bovine serum at 37 degrees C in order to simulate in vivo conditions. In addition, a similar study was completed on specimens, tested in air at ambient temperature for purposes of comparison. Results of this procedure, when analyzed by a Student's t-test at the 95% confidence level with eight degrees of freedom, indicate that both Zimmer and Simplex-P exhibit a higher fracture toughness in the simulated physiological environment. In order to determine whether the addition of barium sulfate to these cements compromises the fracture toughness, the above described testing rationale was repeated, indicating the existence of a complicated relationship between the different testing environments and barium sulfate. The importance of these results lies in the fact that an increased fracture toughness indicates that a cement will inherently exhibit a greater degree of resistance to the propagation of cracks, which could contribute to the ultimate failure of the total joint replacement.
J Biomed Mater Res 1976 Sep
PMID:Fracture characteristics of acrylic bone cements. I. Fracture toughness. 97 7

The health condition of female cash register operators in relation to their working conditions was investigated. A questionnaire study revealed that cash register operators more frequently complained of general fatigue, headache, sleeplessness, and low back pain than female office machine operators or other female workers. Dullness and pain in the shoulder, arm, hand, and fingers especially on the right side were characteristic of cash register operators. Physical examinations in 1973 showed that 31.3% of 371 cash register operators suffered from muscle rigidity or tenderness; 13 were severely afficted and, 69 operators had to be either laid off, reassigned to other jobs, or given shorter working hours. Occupational cervicobrachial disorders were suggested to have been caused by repetitive upper limb motions combined with static load, an unfavorable working environment, and mental stress. Implementation of some improvements including shorter operation time, worker rotation, and adoption of electronic registers proved effective in reducing the number of sufferers of cervicobrachial disorders found during the 1975 physical examinations. But the improvements were not effective enough to alleviate fatigue of the neck, shoulder, and back due presumably to sustaining upper limbs while operating the keyboard.
J Hum Ergol (Tokyo) 1976 Sep
PMID:Health hazard among cash register operators and the effect of improved working conditions. 102 12

An ortho-oblique-type binary data decomposition based on data matrices providing relevant conditions of accidents is proposed as a means of classifying patterns of human error, and the computing procedures are described. The usefulness of the technique is shown by a numerical example of accidents in freight-car classification yard work. Forty-two severely injured victims were interviewed by psychologists and the contents of case reports were rearranged into a reliable binary data matrix which indicated the presence or absence of an interrelationship between each sample and each of 42 items of operational, environmental, and psychological conditions. Three patterns of error leading to an accident were identified by interpreting the orthogonally rotated results. They were 1) failure of strenuous performance in relation to fatigue and poor communication, 2) veterans' mistakes in teamwork, possibly due to hasty operation or distractions, and 3) errors caused by certain defects of machines or inappropriate work space. Recommendations were thus made on training plans for beginners. The importance of using non-scaled accidental data in binary form and allowing rotation for data decomposition is discussed.
J Hum Ergol (Tokyo) 1976 Sep
PMID:Pattern-analytic approach to analysis of accidents due to human error: an application of the ortho-oblique-type binary data decomposition. 103 Jul 29

One-arm cranking was done by ten healthy male adults at an oxygen intake level of about 1.0 liter/min. Each subject performed two kinds of cranking at a speed of 60 rpm: forced cranking using only one arm continuously for 15 min and free cranking for 30 min with the instructions to alternate from one arm to the other whenever fatigue set in. The results, excluding those of a subject who changed arms very frequently, were analyzed. In forced cranking, oxygen intake and heart rate steadily increased, the average time of appearance of local fatigue being 161 sec for the stronger arm and 122 sec for the weaker one. In free cranking, the working arm was changed 6 to 23 times during the 30-minute period, while oxygen intake and heart rate increased with fluctuations. The mean duration interval was 175 sec with the stronger arm and 123 sec with the weaker one. The mean interval of arm alternation was positively correlated with the individual time of onset of the sensation of local rigidness during forced cranking, but not with the individual time of initiation of respiratory distress. It is suggested that alternation of active muscles in moderately dynamic work may be linked with an early stage of local fatigue which is different from that of static work.
J Hum Ergol (Tokyo) 1976 Sep
PMID:Spontaneous alternation of the working arm in one-arm cranking. 103 Jul 31

Fatigue was developed by four human subjects after negative work, and by two subjects after negative/positive work by the jaw muscles. Another four subjects did not develop fatigue subsequent to muscular exercise. In subjects with fatigue, the ability to perceive and/or produce repetitively a predetermined mandibular posture, i.e. mandibular kinesthesia, was impaired by about 285%. It is suggested that the distorted kinesthesia resulted from either a fatigue-induced failure of, or a fatigue-induced persistence of, jaw muscle fibers to contract, which in turn led to distorting flows of afferent impulses from muscles spindles and/or tendon organs.
Scand J Dent Res 1976 Sep
PMID:Mandibular kinesthesia in fatigue of human jaw muscles. 106 8

Of 209 patients who fulfilled the A.R.A. criteria for the diagnosis of systemic lupus erythematosus, 43 were selected for study because each had been treated for at least two years with antimalarials, but had not received antimalarials for at least one subsequent year. In each instance, the antimalarial was discontinued solely because of the development of retinopathy. Each year on antimalarials was matched with a subsequent year off antimalarials for each patient. The year immediately following diagnosis and years of pregnancy were excluded. Paired-t test analysis of matched years revealed that general symptoms (fever, fatigue, weight loss) were less common during years on 500 mg chloroquine daily than during years off the drug (p less than 0.05). Skin manifestations were also less frequent during the years on 500 mg chloroquine daily than during the years off (p less than 0.05). No significant steroid sparing effect was found. However, a greater incidence of flare-ups during the matched years off the drug was statistically significant.
J Rheumatol 1975 Sep
PMID:The efficacy of antimalarials in systemic lupus erythematosus. 110 84

The mechanical properties of 126 motor units from medial gastrocnemius muscle have been studied in 12 adult cats. Units with long contraction times (greater than 45 msec) were non fatigable (24 out of 26 units) and small (25 out of 26 units with less than or equal to 0.3% of the parent whole muscle tetanic tension) thus forming a very homogeneous population. In contrast, fast twitch units (contraction time less than or equal to 45 msec) exhibited a very broad range of tetanic tensions and fatigability. Significant correlations were found, however, within the fast contracting population which indicate a tendency for the more fatigable units to develop more tetanic tension and to be faster contracting. These findings are discussed in relation to the problems associated with using the interrelationships between twitch contraction time, tetanic tension and fatigue resistance to classify motor units into subpopulations sharing similar mechanical properties.
Exp Brain Res 1975 Sep 29
PMID:The motor units of cat medial gastrocnemius: problem of their categorisation on the basis of mechanical properties. 118 7

Brain stem auditory-evoked responses were recorded in 24 infants ranging in age from six-weeks premature to term. At a given age, the latency of the response increased with decreasing stimulus intensity. Further, as age increased, there was a systematic decrease in latency of the response at each sound intensity level. The response was shown not to be fatigue or sleep stage. It may, therefore, be of use for evaluating auditory function in high-risk newborn infants.
J Speech Hear Res 1975 Sep
PMID:Brain stem auditory-evoked responses in premature infants. 118 55

The incidence of drowsings as a cause of near traffic accidents was studied on the basis of daily recordings or near accidental events by 288 locomotive drivers during a rotation period of 2-3 weeks. Of 198 near accidents reported during 2,290 trips, 34 cases, or 1,5 cases per 100 trips, were operation missess involving drowsing or strong drowsiness. Improper operation due to drowsing occurred at a certain rate for any group of drivers, irrespective of the type of train, running sections, weather, and other operative conditions such as train delays, whereas 117 cases of danger caused by unforeseen obstacles on the track were related to site characteristics, and 47 cases of other disorders were frequent in unusual operative conditions such as arrival-departure, poor signal display, wrong instructions, or equipment failure. Thus continued driving under ordinary track conditions at a more or less constant speed was likely to induce drowsiness under the dominant influences of fatigue and time of the day; 79% of such cases occurred between midnight and 6 a.m. Most drowsings on the second night appeared during the first 2-4 hr of duty. Effects of monotony and insufficient rest were discussed in relation to recurrent fluctuation in vigilance.
J Hum Ergol (Tokyo) 1975 Sep
PMID:Incidence of near accidental drowsing in locomotive driving during a period of rotation. 122 12

The addition of carbohydrate and sodium to sport drinks has been recommended to enhance fluid intake and absorption and to delay fatigue. Other electrolytes (E) which are lost through sweating are also commonly added. However, too many E may lead to increased serum E and osmolality levels, which may negatively influence thermoregulation, depress sweating, and cause gastrointestinal distress. On the other hand, drinking large amounts of plain water to compensate sweat loss may induce hyponatremia. Therefore, literature describing sweat E losses was examined in order to estimate average whole-body E loss and to determine an upper limit for replacement of E with sport drinks. Mean E loss was determined from 13 studies, with +/- 1 SD resulting in a hypothetical range for E losses. Correction for net absorption resulted in an upper limit fo electrolyte replacement. It is suggested that the E levels in sport rehydration drinks should not exceed the upper limit of the range given.
Int J Sport Nutr 1992 Sep
PMID:Rationale for upper limits of electrolyte replacement during exercise. 129 95


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