Search

Muscle ATP, CP, ADP, glycogen, G-6-P. lactate, and blood lactate concentration were studied in three subjects during intermittent exercise. One min of extremely heavy bicycle work was followed by five min of rest, which was repeated five times. Oxygen uptake was determined continuously and oxygen deficit could be calculated for each activity burst. Oxygen uptake was also measured during the first 60 min of recovery following the last exercise period. The accumulated oxygen deficit increased with each work period. The ratio between oxygen deficit and oxygen debt was 0.55. The breakdown of ATP and CP stores showed progressive phosphagen depletion with each burst of activity while the muscle lactate concentration reached its highest level, ca 23 mmoles × kg-1 wet muscle, as early as after the first work period. Blood lactate increased gradually during the first 15–20 min of interval periods and then reached a level of 20 mmoles × l-l. Muscle glycogen concentration was reduced with each work period but did not become completely depleted in any of the subjects. The subjects were as exhausted after the first work period as after the last one. Of the studied metabolic variables muscle lactate concentration was then the one best related to the point of exhaustion.

The use of the palmaris longus as the motor for lumbrical replacement is recommended as an operation of choice. This is advocated on the basis of electromyographic studies, the technical ease of the operation and saving of tourniquet time which permits the operation of opponens replacement to be undertaken at the same procedure thus halving the loss of work period. The author wishes to acknowledge the help of the physiotherapists Mr. W. Jennings and Mrs. Naik for assisting in the follow up and assessment of the cases; or Dr. S. Pandya for the electromyographic studies and Mr. S. G. Kamat for the photography and drawings.

Responding by one pigeon was reinforced with food on fixed-interval schedules of 30, 60, and 300 sec duration. A second pigeon was studied under fixed-interval durations of 60 and 300 sec. For both birds, the average post-reinforcement pause was one-half the duration of the fixed interval. Autocorrelation coefficients revealed first-order sequential dependencies in series of post-reinforcement pauses. On the 300-sec fixed-interval schedule, successive post-reinforcement tended to alternate between long and short durations. At the shorter fixed-interval durations there was less evidence of alternation sequences. A second experiment was conducted to determine if the time intervals between the first response after reinforcement and the next reinforcement (the work periods) were responsible for the alternation patterns in the series of post-reinforcement pauses. To evaluate the role of the work period, several procedures were used to modify the work period from that obtained on the fixed-interval 300-sec schedule. Adding a schedule to the fixed-interval schedule that set the minimum amount of time that could elapse between the first response after reinforcement and the next reinforcement eliminated the alternation pattern. Control schedules indicated that the elimination of alternation patterns resulted from constraints on the work period per se and not from confounded changes in the interreinforcement intervals.

27 college students performed a total of 297 work periods, in which the work of lifting a ten-pound weight with the flexors of the middle finger was continued to exhaustion. The following conclusions were drawn: Absolute variability decreases sharply in the early work periods of a series and fluctuates irregularly throughout the remainder of the series. Relative variability shows no regular change throughout the series. The work done with unfatigued muscles (first ten contractions) is more variable in the later periods of the series than in the earlier periods. With fatigued muscles (last ten contractions) there is no systematic change in variability throughout the series. A comparison of the work done in the first ten contractions of each work period with that done in the last ten contractions shows that the mean output of work done with fatigued muscles is one-fifth of that done with unfatigued muscles. The relative variability of work done with fatigued muscles is three times the variability of the work done with unfatigued muscles. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Sixteen healthy male subjects performed a complex choice-reaction task under time pressure. Adrenaline and noradrenaline excretion, heart rate, and subjective reactions were measured before, during, and after the work period and at corresponding points in time in a control session without work. Mean adrenaline excretion, heart rate, and subjective arousal increased significantly during work and returned to baseline levels within 1–2 hr after the end of work. There were large inter-individual differences in the rate at which adrenaline output decreased. When subjects whose adrenaline output decreased rapidly were compared with those whose adrenaline output decreased slowly, it was found that ‘rapid decreasers’ had higher baseline levels of adrenaline, performed better on the choice-reaction task, and had lower scores in neuroticism. The significance of temporal factors in adrenaline-mediated adjustment to environmental stressors is discussed.

Five subjects were trained to tap on a light Morse-key during nerve compression block. The training sessions lasted for 40 sec., with a 5 sec. rest after the first 20 sec. work period. The group learning curve reached 89.5 per cent. level of normal performance by the eighth training session. In the ninth, the testing session, subjects tapped with visual and auditory sense reduction superimposed on the kinaesthetic and tactile impairment of the training condition. Performance in the testing session reached 40.9 per cent. of normal. The sixth subject was trained in the same task as the other five subjects, but the training condition included elimination of cues from all four sensory channels. He reached 79.09 per cent. of his normal tapping performance in the seventh session. These results show that the motor skill of tapping can be relearned in the absence of kinaesthetic cues. Furthermore when the subject has no conscious knowledge of any peripheral sensory cues connected with the ongoing motor activity, learning can nevertheless take place. These findings lead to the hypothesis, that skilled motor activity can be monitored by central processes alone. During the training sessions subjects showed a tendency of tapping in groups of gradually increasing length. It is hypothesized that increased number of taps forming a group gives an indication to the possible mode of action of these central processes.

Summary. 1 The temperature in resting muscles, measured by means of needleshaped thermocouples, shows considerable variation. In the muscles of the extremities it is most generally 34–35.5°. In the thenar the temperature is found to be 4° lower than the rectal temperature. 2 When the subject is sitting still, with the skin exposed, the muscle temperature shows a gradual fall. 3 During dynamic work (51 kgm in 3 minutes) with the flexor muscles of the elbow, the temperature in the biceps rises 1.4–2.05°, the least in the strongest subjects. In the after-period the temperature falls gradually, the faster the less the work has been. Even relatively light work may, however, occasionally lead to protracted displacements of the temperature level in the muscle. 4 For the same subject the temperature rise during the work, with the same work rhythm, is directly dependent upon the magnitude of the work. 5 In experiments of very short duration the muscle temperature rises after the work has ceased, presumably because of inadequate circulation during the work. 6 In dynamic work with heavy load the muscle temperature is found to behave as in static work; conversely, in static work with light load the temperature will behave as in dynamic work. 7 During static work the muscle temperature rises moderately or only very little during the work period, but the rise continues for a shorter or longer period after the work has ceased. 8 This phenomenon is still more pronounced when the circulation to the working muscle group is arrested. Then the high temperature rise will not appear until the circulation is restored. 9 The experiments show that the temperature rise in the muscle in the main is due to processes with positive heat effect in the muscle itself, not to increased circulation. 10 The heat production is mainly due to oxidation processes, but is also observed during and after work with the circulation arrested. The anaerobic heat production is very small, however.

Before, and after 22 weeks of physical training, oxygen uptake, heart rate and cardiac output (dye dilution technique) were measured in 7 male subjects (22 to 26 years old) during pro longed severe exercise (60 min on 75 % of the individual's maximal oxygen uptake) and during exhausting work loads of about 5 min duration. Maximal oxygen uptake increased from 3.41 l/min (48.0 mllkg per min) before to 3.64 I/min (52.0 ml/kg per min) after the training (p

Oxygen consumption curves were obtained during static exercise on 34 young males. The workloads consisted of 70, 100, 130, and 160 Ibs. resistance. At the onset as well as immediately after the termination of the work period sudden changes of the normal (dynamic exercise) pattern of oxygen consumption were noted and explained in terms of circulatory factors. The linear increase in the “debt/income” ratio (oxygen intake during recovery over oxygen intake during work) with the increase in load shows that the circulation becomes increasingly impaired during static contraction. The metabolic cost of static work must be met by a relatively larger debt payoff during the recovery period.

Work-study programs at South Dakota State University during the academic year include part-time work in the university dairy processing plant, in research laboratories, and at the dairy research farm. Summer work experience is gained in dairy processing plants in several states. Students can receive 3 h of academic credit for summer experience and up to 12 credits during a semester. A 10-page guide is provided for employers of workstudy students, and a 4-page mimeograph package outlines responsibilities of the student to the employer. Students write reports of their job experiences. A faculty advisor counsels these students and makes on-site visits during the summer work period.

A self-study inservice educational program on drug information resources was designed to improve staff pharmacist competence in responding to drug information requests. Pharmacists attended two introductory sessions in the drug information center (DIC) that focused on available resources and the systematic search process. Each pharmacist also spent an eight-hour work period in the DIC. Twenty-four hours of regular staff time was allowed for each pharmacist to complete a self-study manual. The manual consisted of three section: (1) discussion of selected references; (2) assignments based on common types of drug information questions; and (3) assignments that required the use of indexing and abstracting sources. Each pharmacist had to complete 50 questions during a 12-week period. The pharmacists were evaluated through pre- and post-tests and by the accuracy of answers to assignments in the manual. Six pharmacists initially participated in the program; five of them attained an average grade of more than 70 on the post-test and assignments. Three new staff pharmacists now have also completed the program. The success of the program depended on the support of pharmacy administration, as well as the motivation of the participating pharmacists. This staff development program using a self-study manual has been an effective means for improving pharmacists' use of drug information resources. The manual is flexible to accommodate differences in the rate of staff development and it is a useful training tool for new pharmacists.

Urinary excretion of thioether before starting work and in the early work period in a rubber factory was measured in urine samples collected after one, two to four, and five or more months of starting work. The study population consisted of 84 new workers. The urinary excretion of thioether decreased after one month's exposure and increased thereafter up to five months. Measurement of urinary thioethers in groups of new workers is therefore informative of exposure to alkylating agents only after several months from starting work. This effect may be mediated by the induction of the pertinent metabolic pathway.

Exposures to benzene vapour were measured in a group of coal tar distillation workers and the concentration of benzene in the air that they exhaled was determined at the beginning of the following work period. Time-weighted average benzene concentrations were principally in the range 0.02-0.9 ppm. Benzene vapour was detectable in the breath of all subjects 16 h after exposure, and a progressive build-up over the working week was found. Nevertheless the relationship between exposure and concentration in exhaled breath was found to be poor. This suggests that at concentrations below about 1 ppm, the analysis of exhaled breath is not a reliable method of measuring previous exposure to benzene.

Twelve young women, athletes (n = 6) and nonathletes (n = 6), walked on a treadmill at loads equivalent to approximately 30% Vo2 max for two 50-minperiods in three environments: 1) 28 degrees C, 45% rh, 2) 35 degrees C, 65% rh, and 3) 48 degrees C, 10% rh. There were no differences between groupsin rectal temperature, heart rate, evaporative heat loss, or mean skin temperature at 28 or 35 degrees C or during the first work period in the 48 degrees C environment. However, a significantly lower cardiac output (Q) andstroke volume (SV) observed for nonathletes by the 46th min of work at 48 degrees C may explain why no nonathletes were able to complete a 2nd h of workwhile four of six athletes successfully finished the period. It appearsthatin conditions of severe heat stress (48 degrees C) athletes were able to maintain a cardiac output sufficient to meet the metabolic requirements and the large increase in peripheral blood flow for a longer period of time thannonathletes.

The effects of a good-behavior contract on the on-task behavior, disruptive behavior, daily assignment completion, and weekly grades of four sixth-grade students were examined in a public school classroom. The contract consisted of presenting the students with a list of good conduct and assignment completion goals and a list of disruptive behaviors coupled with a list of rewards and penalties that could be earned. The rewards and penalties made use of existing facilities and classroom privileges. At the beginning of each morning work period, the teacher negotiated the good-behavior contract with each experimental subject. During the negotiations, the teacher emphasized student self-management and encouraged each student to earn a reward by achieving the good-conduct goals and completing the contract assignments. An isolated work area was provided to allow students the opportunity to remove themselves from their desks for a fixed period of 15 min. At the end of the work period, the teacher determined whether each student earned a choice of reward or penalty dependent on assignment completion and whether the teacher had observed disruptive behaviors. Thus, the contract permitted the student to negotiate the goal behaviors and contingencies with the teacher. Throughout the study, the students were in agreement with the teacher on whether a choice of reward or penalty had been earned. The contract was introduced for different children at different times, constituting a multiple-baseline analysis. On-task behavior and daily assignment completion increased, weekly grades were higher, and disruptive behavior decreased when the contract was in effect. Three contrast subjects were selected from the class as model students who consistently produced acceptable assignments and who did not engage in high rates of disruptive and/or off-task behaviors. When the contract was in effect for the experimental subjects, their performance compared favorably with the contrast subjects, who never received the daily contract. The results demonstrated that the contract was effective within the confines of the facilities and contingencies readily available in a public school classroom setting.

Ten manual metal arc (MMA) high alloy stainless steel (SS) welders were studied during one week and the concentrations of chromium (Cr) and nickel (Ni) were determined in their urine and blood. Stationary and personal air samples were collected from the immediate work environment; they covered the entire work period. Spot urine samples were collected during the follow-up period. Whole blood and plasma samples were taken from the workers before and after one shift, and the retention rate of magnetic dust in the lungs was estimated with magnetopneumography. On the basis of the results, indices of short-term exposure to Cr and Ni were evaluated. Urinary Cr and Ni concentrations (corrected to creatinine) reflect both the body burden caused by long-term and short-term exposure to easily soluble fractions of these metals. The results indicated that the use of Cr and Ni urinary analyses as indices of short-term exposure is not as dependable as previously assumed. The Cr and Ni concentrations in whole blood and plasma did not correlate with the measured exposure, but the daily mean increase in the Cr concentration reflected exposure to total Cr and Cr(VI) very well. The large variation in the Cr concentration of the morning urine (0.01-2.7 mumol/1) and blood (0.05-1.43 mumol/1) indicated large personal variations of body burden among the exposed welders. The retention rate of magnetic dust in the lungs correlated well (P less than 0.01) with the daily mean increase of Cr in blood. Very good correlations (P less than 0.001) were found between the retention rate of magnetic dust and the personal air samples of Cr and Cr(VI).

Three male research volunteers lived in a residential laboratory for 12 days in a study designed to investigate factors controlling patterns of marijuana smoking. All contact with the experimenters was through a networked computer system and subjects' behaviors were continuously recorded. During the first six hr of the day (0945-1545), subjects remained in their private rooms engaging in planned work activities, and during the remainder of the day (7 3/4 hr) they were allowed to socialize (1600-2345). Subjects were instructed that up to five active marijuana cigarettes (1.84% delta 9 w/w THC) could be smoked on designated days between 0945 and 2200. Cigarettes were available on request. Subjects requested all five cigarettes on 15 of 18 possible occasions (three subjects x six days of availability) with a mean latency to the first cigarette of 22 min. The pattern of self-administration was remarkably similar among subjects with all subjects smoking two cigarettes during the private work period and three cigarettes during the social access period. Subjects 1 and 2 smoked 90% of their social period cigarettes together in the social area, while Subject 3 smoked all of his cigarettes alone in his private room.

Contemporary Korean women divers wear wet suits during diving work to avoid the cold water stress. The present study was undertaken to evaluate the effect of wearing wet suits on the daily thermal balance of divers and on the duration of diving work. Rectal (TR) and skin temperatures and O2 consumption (VO2) were measured in four divers before and during diving work in summer (22.5 degrees C water) and winter (10 degrees C water). Subjects wore either wet suits (protected) or cotton suits (unprotected) for comparison. TR decreased 0.4 degrees C in summer and 0.6 degrees C in winter after 2 h of diving work in protected divers, while it decreased to 35 degrees C in 60 min in summer and in 30 min in winter in unprotected divers. Mean skin temperature of protected divers decreased to 31 degrees C in summer and 28 degrees C in winter, while that of unprotected divers decreased to 24 degrees C in summer and 13 degrees C in winter. VO2 toward the end of the diving work period increased by 80 (summer) and 140% (winter) in protected divers and by 160 (summer) and 250% (winter) in unprotected divers. From these values total thermal cost of diving work was estimated to be 260 and 370 kcal . day-1 in summer and winter, respectively.

Truck driver safety was studied under conditions of prolonged normal driving, prolonged continuous convoy during, and continuous convoy during under conditions of task uncertainity. In all experiments drivers were required to drive an experimental truck for four consecutive days. Dependent variables were driver performance, self ratings, and endocrine changes. Apart from changes over time, where possible the effects of age and time of work period onset were determined. Symptoms of fatigue were most typical of the end of the driving shift, becoming evident from about the 9th hour of driving, and were particularly characteristic of older drivers on a shift finishing at 02.30 hours. Nevertheless the requirement to drive 11 hours per day for 4 consecutive days did not lead to conspicuous deterioration in driving performance under normal driving conditions. Even under continuous convoy driving such prolonged work did not produce impairment but elicited compensatory adjustments toward the end of the late shift. Finally, task uncertainity was not found to induce earlier fatigue. Drivers appeared to adjust to this condition by covertly anticipating a demand in excess of actual requirement. A behavioural analysis of the driving task was proposed and among other features its implications for driver fatigue and traffic accidents were discussed.

Individual differences in pupil size are not surprising since they have been well documented by ocular scientists for years, although emphasis has typically been on abnormalities. What may be surprising, however, is the possibility that some of these presumably inherent differences may be related to performance characteristics of the individuals. I would like to discuss some research which suggests that certain pupillary measurements may be useful as performance predictors of individual capabilities, and/or group behavior. Before describing the first study (Peavler, in press), a brief review of some of the previous pupillary research seems appropriate.

It is argued that effects of fatigue on performance should be progressive as time goes on. Initial decrements, often found in vigilance tasks, cannot be ascribed to what is usually called fatigue, but rather reflect a change from a state of hyper-vigilance to normal vigilance occurring within the first half hour of the work period. Studies on very long-term performance, in particular longterm driving, have generally failed to show progressive effects. This casts some doubt on the usual implicit assumption that fatigue and long-term work are uniquely related. It is probable that effects of declining diurnal rhythm, monotony, and accumulating lack of sleep will also contribute to fatigue.

Early studies suggested that the effects of varying length of work period (TW) and duration of rest period (TR) are additive when TW and TR alternate and are constant within experimental conditions. Recent investigations indicate that the joint effect of these variables on performance depends on the ratio TW:TR. this ratio effect is not predicted by functions traditionally used to describe theoretical massing and distribution effects. Parabolic functions were suggested and were shown to describe reminiscence data adequately. College students were given 30 min, of rotary pursuit practice with 10- or 30-sec work periods alternating with 5-, 10-, or 30-sec rest intervals (n = 30 per group). Predictions that work and rest variables would have orthogonal effects while final performance levels could be described as a parabolic function of the ratio TW:TR were confirmed.

Fuzzy set theory was applied to develop capacities models for combined manual materials-handling (MHH) activities. These models can be applied to job design/redesign to reduce the risk involved to the human operator. Twelve male subjects were employed for this study. The capacities for four individual MMH activities (lifting from floor to knuckle height, lifting from knuckle to shoulder height, carrying for 4.3 m, and lowering from knuckle to floor height) and three combined MMH activities, which were the combination of the above four individual activities, were determined psychophysically under three frequency conditions: one time maximum, 1 handling/min, and 6 handlings/min. In all experimental conditions, the pyschophysically determined capacities were the maximum acceptable work loads for a one-hour work period. The models were developed to combine two individual MMH capacities into a combined MMH capacity using fuzzy set theory. Membership functions and reference points were determined from the previously published literature. These models were tested from the experimental data in this study. The mean absolute error was 5.2%.

Most psychophysical studies in manual materials handling (MMH)are involved only with single MMH activities, i.e. lifting, lowering, carrying, holding, pushing or pulling. Very little research has been reported on the determination of operator capacities for combinations of MMH activities (e.g. lifting a box, then carrying the box, or carrying a box, then lowering the box). These kinds of combined activities are prevalent in industry and in our daily lives. The objective of this study was to utilize the psychophysical approach to examine the effects of combinations of lifting, carrying and lowering activities. Twelve male students served as subjects for the study. The capacities that were determined as the maximum acceptable workloads for a 1-h work period for four individual MMH activities—lifting from floor to knuckle height (LFK), lifting from knuckle to shoulder height (LKS), lowering from knuckle to floor height (LOW) and carrying for 3·4 m (C) —and three combined MMH activities—LFK + C, LFK + C + LKS...

In prolonged work periods, men and women often forego satisfying their sleep need to complete their assigned jobs, resulting in an accumulation of performance/mood degrading sleep loss and fatigue. Sleep need can be satisfied only by a slow process of sleeping for an average of 7 to 8 consecutive hours per 24 hour period, i.e., a long period of 'time-out.' However, sleep management suggests that recovery from fatigue and sleepiness during a prolonged work period can be accomplished by short or ultra-short sleep (naps) taken during a prolonged work period. Naps are shown not only to refresh and restore human functioning, but also to maintain performance and mood during a prolonged work period. In this paper, naps' power as a counter-degradation measure are described first through the literature review, and then through critical evaluation of studies conducted at the Defense and Civil Institute of Environmental Medicine, Canada and the Naval Health Research Center.

Mental load and strain in the work of firemen and fire alarm center operators were studied in a group of 260 fireman and 6 female full-time operators from three fire brigades. The firemen proved to be satisfied with their work, and signs of chronic psychological problems were uncommon. Situational work load and related strain may, however, be extreme during active operations. A large proportion (42%) of the firemen suffered from strain after the 24-h long daily work period. Those who had recently worked as paramedics in the ambulance service or in the alarm center were under more strain than ordinary fire fighters. Biochemical stress indicators revealed a high activation of firemen at the alarm center. The difference found between firemen and full-time female operators may be due to a variation in the adaptive functions of the two sexes.

Plasma citrate was determined in seven subjects working 45 min at 50-60% of their maximal aerobic power and in six subjects who were exercised intermittently for five periods of 1 min at supramaximal work loads. Determinations of plasma lactate, glucose, free fatty acids and insulin were carried out simultaneously. During submaximal work the mean plasma citrate concentration decreased from 116 +/- 4 mumol/1 at rest to 108 +/- 5 mumol/1 after 10 min exercise (P less than 0.05) and increased above resting level to 136 +/- 5 mumol/1 40 min after cessation of work (P less than 0.05). During intermittent supramaximal exercise, mean plasma citrate concentration rose after the third work period and during recovery from 117 +/- 6 mumol/1 at rest to 181 +/- 9 mumol/1 40 min after last work period (P less than 0.05). Plasma citrate varied similarly to variations in plasma free fatty acids and inversely to changes of lactate concentrations during submaximal exercise. Opposite interrelationships were demonstrated during intermittent supramaximal exercise. Plasma citrate concentration varied in the same way as might be expected for changes in cytosolic citrate levels of muscle from in vitro knowledge of the regulatory role of citrate on glucose oxidation.

The effects of repetition on the Wilkinson Vigilance Task and an unobtrusive performance measure (crossword completion) were examined in 18 subjects over two 8 h work periods. Vigilance trials alternated with breaks in 25min segments across a work period from 0900 to 1700 h and a period from 2400 to 0800 h. Performance decrements were seen in hit rate and on the irrelevant task measure across the night session, and in hit rate across the day session. Decrements were greater at night than during the day on both measures. The number of attempts on the vigilance task decreased across trials similarly in both testing sessions. It was concluded that specific task repetition results in performance decrements, even when circadian incremental effects would be predicted, and that the placement of such task repetition at night magnifies those decrements and extends them to intrinscially as well as extrinsically motivated tasks.

This is the fifth quarterly technical report on a program to prepare a high explosive safety manual for the Department of Energy. The program is described and progress to date is presented. During this work period, the first draft of the manual was completed and the quantitative risk analysis begun.

1. The diencephalon of the unanaesthetized macaque monkey was radio-labelled with calcium by a microinjection of 6-8 muC (45)Ca(2+) into the third cerebral ventricle through a permanently implanted cannula. Successive 5 min push-pull perfusions of the mid-line hypothalamic region with an artificial C.S.F. were carried out at a rate of 28 mul./min every 20 min. A washout curve of declining (45)Ca(2+) radioactivity was thus generated.2. When the monkey exercised strenuously on a special ;rowing machine' to obtain highly palatable banana pellets, its body temperature rose sharply. As the monkey exercised, during a sequence of push-pull perfusions, the concurrent efflux of (45)Ca(2+) ions increased markedly in the corresponding samples of diencephalic perfusate. This enhanced activity of calcium ions continued throughout a 30 min work period and persisted as long as the monkey's temperature was elevated in the interval immediately following exercise.3. Exposure of the monkey's trunk, between neck and thigh to cold air of 5 degrees C likewise augmented the amount of (45)Ca(2+) ions in the diencephalic push-pull perfusates; however, a similar exposure to air warmed to 35 degrees C failed to alter the pattern of (45)Ca(2+) efflux from the animal's diencephalon. If a fasted monkey consumed only the banana pellets but was not exercised, the level of (45)Ca(2+) in the perfusate also increased transiently, just at the onset of feeding.4. We conclude that a local change in calcium transport, binding or other cellular activity of the cation within the diencephalon could play an important role in the central mechanism underlying the set-point rise in a primate's temperature which accompanies vigorous exercise. Further, the results support the idea that this cation functions in the diencephalic control of metabolic heat production as well as in the overall processes of energy metabolism, particularly in relation to feeding.

Pulse rate and energy expenditure were measured on fifteen male subjects who had been given ergometer cycling of ‘O’ and 32·6 W to 97·8 W in three temperatures of 22°C, 30°C, and 37°C. The variation in pulse rate of each graded work period was compared with the variation in energy expenditure for each environmental temperature. The pulse rate was significantly increased with the rise of environmental temperature (p <

Manual flax processing originated in Egypt in 2 000 BC. In the present study a representative sample of the workers involved in this trade, where flax is processed in small workshops or homes, was examined, and their dust exposure was evaluated. The study showed that workers handling and processing flax are exposed to high concentrations of dust; the levels of dust at hackling and combing are considerably higher than at batting and spinning. Byssinosis prevailed in 22-9% of the examined workers, and 18-4% of them had their forced expiratory volume in one second reduced by more than 10% at the end of the first morning work period (4 hours) of the week. Both the rates and the grades of these syndromes increased with duration of exposure. Smoking appeared to be one of the important contributory factors in the production of byssinosis. The relationship between dust concentration and prevalence of byssinosis seems to be curvilinear.

The experiments described in this chapter are of particular interest, for two reasons. In the first place, reminiscence seems to be a particularly stable and sensitive index of motivation; the well-known difficulty of finding many such indicators suggests that we should cherish those we have found with particular care. In the second place, the use of motivation as the independent variable in our experimental design enables us to perform what seem crucial experiments to decide between the inhibition and the consolidation theories.

1. Seven healthy male volunteers performed intermittent exercise (15 sec work--15 sec rest) at a high work load for 60 min and six subjects performed continuous exercise at an equally high load to exhaustion, which occurred after 4--6 min. 2. Muscle biopsies were obtained from the lateral portion of the quadriceps muscle before intermittent exercise and after the end of a work period and the end of the subsequent rest period at 5, 15, 30 and 60 min of exercise, as well as before, immediately after and about 15, 30, 60 and 180 sec after continuous exercise. 3. The reduction in glycogen content was smaller and glucose-6-phosphate, glycerol-1-phosphate, lactate and malate contents were lower after both work and rest periods in intermittent compared with continuous exercise, indicating a lower rate of glycolysis. 4. ATP and CP levels had decreased at the end of work periods in intermittent exercise but increased to slightly below basal in the subsequent rest periods. A still larger decrease in ATP and CP levels was found after continuous exercise to exhaustion and a progressive increase occurred over the 3 min of recovery. 5. In each rest period during intermittent exercise citrate levels increased to reach above basal. They increased also in the recovery phase after continuous exercise, although more slowly. 6. The findings support the assumption that ATP, CP and citrate act as regulatory factors of glycolysis in human muscle by retarding certain rate limiting steps. The increase in G-6-P/F-1-6-P2 ratio in rest periods of intermittent intense exercise and in the recovery phase of continuous intense exercise suggests that glycolysis is retarded at the phosphofructokinase reaction. 7. The factors mentioned may therefore contribute to the relative increase in lipid utilization during intense intermittent compared to continuous exercise.

Fifteen adult male research volunteers, in five groups of three subjects each, lived in a residential laboratory for up to 20 days. All contact with the experimenters was through a networked computer system, and subjects' behaviors were monitored continuously and recorded. During the first part of each day, subjects remained in their private rooms doing planned work activities, and during the remainder of each day, they were allowed to socialize. One or two cigarettes containing active marijuana (1.3–2.7% Δ 9 -THC) or placebo were smoked during both the private work period and the period of access to social activities. Two- or three-day contingency conditions requiring subjects to engage in a low-probability recreational activity in order to earn time that could be spent engaging in a high-probability recreational activity were programmed during periods of placebo and active marijuana smoking. During placebo administration, the contingency requirement reliably increased the amount of time that subjects spent engaged in the low-probability instrumental activity and decreased the time spent engaged in the high-probability contingent activity. During active marijuana administration, however, the increase in instrumental activity were consistently smaller than observed under placebo conditions. The decreases in high-probability contingent activity were similar across drug conditions. Smoking active marijuana was thus observed to produce instrumental decrements under motivational conditions involving recreational contingencies.

Off-gas samples obtained during operation of the blanket recombiner at hydrogen flow rates between 0.2 and 2.0 scfm indicated complete recombination with excess oxygen of 0.1 scfm and a steam dilution of 2 lb/min. The catalyst bed temperature varied linearly with hydrogen flow rate from 165 deg C at 0.2 scfm to 290 deg C at 2.0 scfm. (auth)

Urinary excretion of catecholamines was studied in 240 normal, healthy children 12 years of age during a passive condition (film exposure) and an active condition (arithmetic test) at school. No sex differences in catecholamine excretion were found during the passive condition, whereas, during the work period, boys excreted significantly more adrenaline and noradrealine than girls. A comparison is made between catecholamine excretion levels of the children and adult subjects examined in other studies.

Following five days of physical, psychiatric, and psychological examination and two days of indoctrination and training, volunteers were subjected to a simulated flight of seven days duration in a one-man hermetically sealed chamber.

The understanding of muscle metabolism and its regulation in situ has been greatly advanced in recent years by the analysis of the levels of metabolic intermediates under differing conditions. Only recently has it been possible to perform similar studies in mail. In the present studies muscle samples have been obtained using the needle biopsy technique (1, 10, 11) and the levels of a number of metabolites in these have been determined by enzymatic micro-methods.

It has been shown that when experienced workers in industry, engaged on repetitive method-studied tasks, are free to work at their own pace, their performance displays a highly consistent pattern, the principal feature of which is the absence of any trend in operation times throughout the work period (Chapter 7).

The aim of the present research was to investigate further the possible r81e of myohemoglobin as an oxygen-store during the initial stage of muscular work. One subject worked intermittently with a work load of 2,520 kpm/min with varied duration of work and rest pauses on a bicycle ergometer. A highly significant difference in the blood lactic acid concentration during the experimental time of 30 min was found, at work with short work periods (10 sec, lactic acid concentration about 10–20 mg per 100 ml) compared with relative long ones (60 sec, lactic acid concentration 110–140 mg per 100 ml). The conclusion was drawn that the first type of work is performed aerobically. The calculated oxygen demand, during the work period of 10 sec, however, does not correspond to the measured oxygen intake. A deficit of about 0.43 1 O2 for each period of work will occur. It was suggested that this amount of 0.43 1 O2 is supplied to the working muscle mainly from oxymyo-hemoglobin. This store function of myohemoglobin is discussed in relation to the present findings and to the results mentioned in the literature.

A vigilance task was performed in which regular flashes of light were monitored for an occasional flash of greater brightness. Following every flash a decision of signal present, signal absent, or doubtful had to be recorded. Two separate groups received high and low signal rates with a variety of the task in which the flashes occurred only on one lamp; another group received a high signal rate divided between three simultaneously flashing lights. An analysis in terms of decision theory showed that detrimental changes during the watch period were entirely attributable to movement of the subject's criterion for reporting a signal: his sensitivity to the signals if anything improved during the work period. In addition, criterion changes in the presence of intense noise occurred at high signal frequencies, even when only one source of information was involved: thus showing that division of attention between different sources is not essential for harmful effects of noise. In addition, criteria under quiet conditions were different at different signal rates.

We have recently been interested in the physiological adaptations accompanying the performance of a given total amount of work by a variety of patterns of intermittent and continuous exercise.

An overview of introduction of Sitka spruce in Estonia. First reports of cultivation of Sitka spruce in Estonia come from 1879. In 1895, Peravalla forest area (now Järvselja) obtained a small amount of seed from Thüringen. Saplings from that seed were planted in the forest in 1904, but for 1928 all trees were perished. During the 20th century, seed of Sitka spruce from different provenance of the natural distribution area was repeatedly sown and seedlings grown in Järvselja and some other places in Estonia, but all the cultivation attempts failed sooner or later. There are no Sitka spruces remained from the pre-War period in the mainland part of Estonia. In 1984, a group of saplings from seed of 1978 was planted in Järvselja. These trees are 15 m mean height with 20.6 cm mean diameter now. In 1975, a small group of large Sitka spruces was found growing in a remote forest park of Suuremõisa Manor, island of Hiiumaa. These Sitka spruces were revisited by us in spring 2018, to measure the trees and determine their age by tree rings. Nine trees out of 13 bigger spruces were cored. Age of the trees exceeded nearly 120 years. The planting time coincides with work period of Karl Ahrens, the forest officer of Suuremõisa Manor at that time. In spring 2018, the mean diameter at breast height (DBH) of the tree group was 62 cm and mean height ca 36 m. The biggest tree had DBH 101 cm (with 37 m height) while the maximum height for the tree group was 38 m. The Suuremõisa group of Sitka spruces on 0.02 ha is remarkable by its dense stand. If to extrapolate to one hectare, the growing stock of the stand would exceed 3 thousand cubic meters. The vital group of Sitka spruces at Suuremõisa have proved that this foreign tree species can grow rather well in the western islands and coastal region of Estonia. Sitka spruce can grow faster than native Norway spruce in Estonia. Future decades will show the viability of Sitka spruce cultures in the mainland of Estonia.