Physiological requirement, definition

In human exercise physiology, fatigue is often defined as an inability of a muscle or a group of muscles to sustain the required or expected force (Edwards, 1981). This definition is very applicable for the study of factors limiting dynamic or isometric exercise in intact organisms at varying intensities. 

The impact of the root to shoot ratios on calculated maintenance requirements is important because root to shoot ratios are highly variable and almost always underestimate below-ground biomass. Amos and Walters (2006) reported that the net below-ground C deposition in com at physiological maturity was 29% 13% of the shoot biomass (leaves, stems, and husks) in 41 studies. The use of these values is further complicated by the use of different definitions for root to shoot ratio. Converting Amos and Walters (2006) units to units used by Johnson et al. (2006) would reduce the reported values from 0.29 to 0.15 (harvest index 50%). 

Study of plasma catalase activity on an individual basis has been limited in scope. For 50 adults the range was found to be from 4.2 to 9.5 per ml. of plasma. 19 One of the normal individuals was studied for five days, and the following values were obtained 9.5, 8.5, 9.5, 7.0, 9.5. Further study is required before one could conclude definitely that there are significant inter-individual differences. The available evidence points in that direction. In various anemias the values may be 50 or more. In one "diagnostic problem case" the value was 42. It seems highly probable that "normal" differences have physiological significance. 

The response of the Anerican public to utilize diet and exercise for maintenance of health has increased the need for more definitive scientific information about the interactions of exercise with dietary needs. This book reviews some of the physiological and metabolic changes that occur during exercise training and examines the impact of routine exercise on nutritional requirements. 

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