Download rodahl physiology of work pdf

He is author and coauthor of several anatomy and physiology textbooks. Sigmund B. He earned his PhD from Yale University in Since he has researched and taught at the graduate level with emphasis on exercise and work physiology. Dahl,Sigmund B. Stromme libros ebooks, Textbook of Work Physiology Libro pdf gratis. Written by world-renowned exercise physiologists and sports medicine specialists, the new edition retains the important historical background and exercise physiology research conducted by the authors over the past 40 years.

The book addresses the application of this information to the fields of exercise physiology and work physiology. In the following, we shall attempt to present a brief review of some of the more important factors affecting our ability to perform physical work, based on Figure 3. Service functions As already pointed out, the ability to perform physical work basically depends on the ability of the muscle cell to transform chemically-bound energy in the food which we ingest, into mechanical energy.

This in turn depends on the capacity of the service functions that deliver fuel and oxygen to the working muscle fiber. This involves intake, storage and mobilization of nutrients fuel , and the uptake of oxygen through the lungs and the delivery of this oxygen by the cardiovascular system to the muscles for the oxidation of the fuel for the purpose of providing energy.

Training and adaptation Some of these service functions are subject to improvement by physical training. An important part of this training effect is an increase in the stroke volume of the heart, which causes an increase in the cardiac output, augmenting the oxygen transport from the lungs to the muscles Saltin et al.

A study of assembly-line operators showed that the physically fit workers were less fatigued at the end of the work shift than were those who were unfit Hettinger and Rodahl, a. A certain amount of adaptation of the energy-yielding processes, and some of the service functions supporting them, may take place under certain adverse environmental conditions. Thus, exposure to hot environments may within a week or so cause a beneficial acclimatization to heat, causing better heat tolerance due to more efficient sweating, lowered skin and body temperature, and a reduced heart rate Lind and Bass, ; Figure 3.

Prolonged exposure to reduced barometric pressure at high altitude leads to compensatory acclimatization changes involving increased pulmonary ventilation, increased haemoglobin concentration in the blood, and increased capillarization, myoglobin content and modified enzyme activity in certain tissues.

Changes in heart volume with bed rest, followed by physical training from Saltin et al. Different symbols correspond to individual subjects. This relationship, however, is by no means absolute or clear cut. Thus, remarkable accomplishments have been achieved by highly motivated but handicapped or disabled individuals, who were far from healthy.

On the other hand, apparently healthy individuals may feel unable to contribute their share of work, due to a variety of subjective complaints. It is not always a matter of being absolutely healthy or completely sick, but of being somewhere in between, or in the process of becoming less well or less sick. The point at which the individual feels sufficiently sick to stay away from work, may depend on the type of work to be performed, but may at any rate vary greatly from one person to the next.

However, some of these ailments may prevent the individual from doing certain jobs or from working under certain environmental conditions, such as excessive heat or abnormal atmospheric pressures. In the individual assessment of fitness for work in such cases, the clinical work physiologist may be of help in performing specific laboratory tests such as work electrocardiography, or similar stress tests, as well as ambulatory recordings of EGG, heart rate, blood pressure and body temperature on the individual during the performance of his work at the actual work place.

Mean values for maximal oxygen uptake maximal aerobic power in male and female subjects 4 to 65 years of age from I. Sex Basically speaking, there are few jobs which cannot be equally well performed by females as males, except in cases where heavy lifting or very heavy physical work loads are involved. As a matter of fact, experience has shown that women may, in many cases, be superior to men, especially in jobs requiring accuracy, patience, alertness and perseverance.

Women are better able to identify substances by smell than are men; their hearing is better, especially in the case of high frequency sounds, and they maintain a better hearing as they become older than do men. For references see Velle, The maximal aerobic power, i. This means that women exposed to the same physical work load as men may have to exert themselves some 25—30 per cent more than men for the same salary. In the case of light to moderate physical work, however, this may not be of any practical importance.

Women have approximately the same maximal oxygen uptake per kilogram of fat-free body mass as men Figure 3. Maximal oxygen uptake in male ana female subjects, 4 to 33 years of age, in relation to body weight modified from P. Changes in maximal muscle strength with age in women and men are shown in Figure 3. The increase in muscle strength in children is definitely a consequence of growth. In children up to the age of ten to twelve years, there is no significant difference in strength between boys and girls.

After this age the boys continue to become stronger, while the girls gradually level off. The difference is mainly caused by differences in muscle mass 25—35 per cent of the body weight in women, as against 40—45 per cent in men.

Thus, the maximal strength per unit of cross-sectional area of the skeletal muscle is about the same in men and women of all ages. Changes in maximal isometric strength with age in women and men by courtesy of E.

Body size While aerobic power and muscle strength are related to body size and muscle mass, body size as such is rarely a limiting factor in industrial performance. In terms of the energy cost of transporting the body by locomotion, the most efficient vehicle known is a human being on a bicycle, requiring only one-fifth of the energy used when the same human being is walking Diamond, Yet, the natural evolution never created the wheel. Age Maximal oxygen uptake, heart rate, stroke volume, pulmonary ventilation, and muscle strength decrease significantly with old age Figure 3.

In both sexes, the maximal aerobic power reaches a peak at the age of 18—20 years Figure 3. At the age of 65, the mean value is about 70 per cent of what it is for a year old individual.

The value for a year old man is, on the average, roughly the same as that of a year old woman. As is evident from Figure 3. The rate of decline in muscle strength with age is in both sexes greater in the leg and trunk muscles than in the strength of the arm muscles Grimby and Saltin, The decline in muscle strength with age is due to a decline in muscle mass, due to a reduction in the number of motoneurons.

A decline in muscle strength of about 30 per cent from the age of 30 to the age of 75 coincides with a 30 per cent decline in the urinary elimination of creatinine, suggesting a muscular atrophy of this magnitude Figure 3. Nutritional state In carefully controlled laboratory studies varied nutritional states in terms of caloric and protein intakes over a day period had no appreciable effect on physical performance at room temperature.

However, a combination of nutritional deficiency and cold stress had deteriorating effects on performance Rodahl et al. Similarly, Crowdy observed no apparent negative effect on performance in troops living on restricted rations for limited periods of time.

In a study of military cadets exposed to considerable work stress during a 5day period on reduced dietary intakes combined with sleep deprivation, it was shown that dietary supplements did not affect performance significantly, while sleep did Opstad, Individual differences Individual differences in special skills or functional capabilities, whether genetically endowed or not, may certainly play a role in many types of occupations where such special skills and capabilities are essential aircraft pilots etc.

This emphasizes the importance of proper selection procedures. The magnitude of individual differences in performance capacity may perhaps best be illustrated by considering the wide scatter of such a basic function as the maximal oxygen uptake in a group of individuals of the same sex and of the same age.

Traditionally, certain jobs may have been looked upon as being typically suited for men, others for women. While this may have changed with changing trends in the industrialized parts of the world, these attitudes may still persist in more primitive societies. Motivation Motivation plays a major role in all kinds of human pursuits. Biologically speaking, the basic concept of reward and punishment still plays a basic role in determining our attitude towards work, and our willingness to employ all our resources in the pursuit of our goals.

This aspect of our state of mind is closely associated with an awareness of a personal role in the working team or in the job. A strong sense of responsibility may cause an individual to feel that he would be missed, or that he would let his co-workers down, if he failed to show up for work. In many cases, a system of piece work as opposed to fixed salary, may be an incentive to work harder.

In most individuals, a role of responsibility may in itself be a motivating factor. Sleep deprivation Sleep deprivation, when severe, i. This includes information-processing, perceptual-motor tasks, word recall, mathematical problem solving, visual vigilance tasks, auditory tasks and memory tasks. The effect is particularly noticeable in the case of sustained or continuous mental tasks Asken and Raham, Emotional effects are even more conspicuous after several days of sleep deprivation, including depression, hostility, anxiety, tension, confusion and even hallucinations.

In a study of sleep-deprived military cadets it was found that three hours of sleep caused a marked improvement in performance Opstad, Stress with which one is unable to cope, on the other hand, may affect the individual subconsciously, making him preoccupied with the problems involved. This may block his ability to concentrate on the task confronting him, and to cope with the situation which may develop.

Examples of this have been seen in wartime fighter pilots during combat, commercial pilots and in people involved in traffic accidents. Nature of work to be performed Type of work physical or mental The human being is unique among mammals in that he utilizes an exceptionally high proportion of his overall energy output in his central nervous system Mink et al.

The energy metabolism of the central nervous system is extremely high, even at rest. Most studies in the past have failed to detect any significant increase in the overall energy metabolism of the body during mental activity such as thinking or problem solving, unless it is associated with some form of physical activity involving muscle contractions. Recent measurements have shown, however, that when subjects are engaged in pure mental activity, regional cerebral oxidative metabolism, in several areas of the brain, increases, and so does regional cerebral blood flow.

This also includes the cerebellum. Physical work Physical work performed by the human body is accomplished by muscular contractions, supported by oxidative metabolic processes in the muscle cells, in which fuel essentially carbohydrate and fat is oxidized in the presence of oxygen.

For each liter of oxygen utilized, some 5 kcal about 20 J of energy is liberated. Oxygen uptake, therefore, is an expression of the rate of energy output or rate of work Figure 3. The mechanical efficiency of the human body as a work-producing machine is roughly 20—25 per cent, or similar to that of an automobile engine. Since all life functions generally consist of rhythmic, dynamic muscular work in which work and rest, muscle contraction and relaxation, are interspersed at more or less regular, fairly short intervals, the ideal way to perform physical work is to perform it dynamically, with brief work periods interrupted by brief pauses.

This routine will provide some rest during the actual work period, so the worker may avoid fatigue and exhaustion and be able to leave the workplace with sufficient vigour left over for the enjoyment of leisure. Work load As already mentioned, work load may be expressed in terms of liters of oxygen uptake per minute.

Examples of the energy cost of a variety of common everyday activities are given in Figure 3. In view of the fact that maximal aerobic power, i. Suppose two men are to perform the same task, such as carrying a heavy load uphill, requiring an energy expenditure of about 2 liters of oxygen per min. One of the individuals has a maximal oxygen uptake of 6. In the first case, the individual is merely taxing 30 per cent of his aerobic power.

Furthermore, he can continue to cover more than half his energy expenditure from the oxidation of fat, since his metabolic processes are essentially aerobic at this low relative work load. Participation in physical activity and cardiovascular fitness have different effects on mental health and mood.

Pulmonary limitations during exercise: A review. Walking to Health. Int J Exerc Sci 5 2 : , Autonomic changes induced by pre-competitive stress in cyclists in relation to physical fitness and anxiety. Health Promotion and Exercise Training. Related Papers. Abstract Topics 1, Citations Related Papers.