Muscular work

Hultman, E., Bergstrdm. J., McLennan-Andersson, N. (1967). Breakdown and resynthesis of phosphorylcreatine and adenosine triphosphate in connection with muscular work. Scand. J. Clin. Lab. Invest. 16, 56-66. 

McGilvery, R.W. (1975). The use of fuels for muscular work. In Metabolic Adaptations to Prolonged Physical Exercise (Howald, H. Poortmans, J.R., eds.), pp. 12-30, Birkhauser Verlag, Basel. 

Three principal components of the cytoskeleton are microfilaments of 6 nm diameter, microtubules of 23-25 nm diameter, and intermediate filaments of 10 nm diameter. A large number of associated proteins provide for interconnections, for assembly, and for disassembly of the cytoskeleton. Other proteins act as motors that provide motion. One of these motors is present in myosin of muscle. This protein is not only the motor for muscular work but also forms thick filaments of 12-16 nm diameter, which are a major structural component of muscle (see Fig. 19-6). 

Muscular work is accompanied by the production of ammonia, the immediate source of which is adenosine 5 -phosphate (AMP).301 302 This fact led to the recognition of another substrate cycle (Chapter 11) that functions by virtue of the presence of a biosynthetic pathway and of a degradative enzyme in the same cells (cycle A, Fig. 25-17). This purine nucleotide cycle operates in the brain303 304 as well as in muscle. The key enzyme 5-AMP aminohydrolase (AMP deaminase step a, Fig. 25-17) also occurs in erythrocytes and many other tissues.304 305 Persons having normal erythrocyte levels but an absence of this enzyme in muscles suffer from muscular weakness and cramping after exercise.306... 

Heats of combustion of foods and their relation to dietary requirements ha e been thoroughly studied. The food ingested daily by a healthy man of average size doing a moderate amount of muscular work should have a total heat of combustion of about 3000 kcal. About of this is made available as work and heat by digestion and metabolism of the food. 

It was important to note the sufficient decrease (to 25-30%) of carnosine amount after exhaustive muscular work [76]. This was not accompanied by appearance of histidine or P-alanine, which was in agreement with the absence of camosinase in skeletal muscle. This fact illustrated that carnosine is involved in metabolic processes when supporting functional activity of skeletal muscles. These processes can include interaction with ROS and neutralization of glycosyl radicals. 

To calculate energy requirements in an individual, it is necessary to take into account BMR, physical activity (muscular work), age, sex, height, and weight (Appendix I). The energy requirements of muscular work can be measured. Table 5-4 lists the energy expenditure for various physical activities. 

K5. Kennaway, E. L., The effects of muscular work upon the excretion of endogenous purines. J. Physiol. London) 38, 1-27 (1909). 

KHAT OR QAT Catha edulis (Vahl) Forsk. Ex. Endl., family Celastraceae, grows in East Africa. It is cultivated in the mountainous regions (above 1,500 m) in Ethiopia, and Kenya. In countries such as Yemen, the fresh leaves are chewed or used for preparing tea, which is used as a stimulant. Khat counteracts fatigue, facilitates strenuous muscular work, and causes talkativeness. These effects depend on the occurrence in the fresh leaves of the labile alkaloid cathinone, which quickly breaks down into pseudoephedrine. The effects of cathinone are similar to those of amphetamine and there... 

Fat in the body is a major storage site for energy from food eaten in excess of need. The storage of fat is a valuable evolutionary mechanism for people who must live a feast-or-famine existence. The ability to store energy in adipose cells as fat is thought to have contributed to the survival of early humans in times of famine. In addition, fats provide most of the energy needed to perform much of the body s work, and especially muscular work. Fat is the major, if not most important, fuel for light- to moderate-intensity exercise. 

Rohmert, W. (1973a), Problems in Determining Rest Allowances. Part 1 Use of Modern Methods to Evaluate Stress and Strain in Static Muscular Work, Applied Ergonomics, Vol. 4, No. 2, pp. 91-95. 

Demands for response/activity 3.1 Body postures 3.2 Static work 3.3 Heavy muscular work 3.4 Light muscular work, active light work 3.5 Strenuousness and frequency of moves... 

Physical The ability to accomplish sustained, effortful muscular work. 

Chemists have traditionally used calories as the unit of chemical energy. Nutritionists have used kilocalories, or 1000 cal, to express food energy. Ergonomists have used Joules as the metric unit of work. Because energy forms are interchangeable, these units can each be converted into the others, allowing us to calculate the amount of muscular work able to be theoretically obtained from a hamburger. 

Veiersted, K. B., Westgaard, R. H., Andersen, P. (1993). Electromyographic evaluation of muscular work pattern as a predictor of traplezius myalgia. Scandinavian Journal ofWork and Environmental Health, 19, 284-290. 

Murlin J, Riche JA (1916) The fat of the blood in relation to heat production, narcosis and muscular work. Am J Physiol 40 146... 

---