[Interconnection of carbohydrate and lipid metabolism in various modes of muscle activity]. / Vzaimosviaz' metabolizma uglevodov i lipidov pri razlichnykh rezhimakh myshechnoi deiatel'nosti.

The activity of hexokinase and lipase has been determined in skeletal muscles of different metabolic types and adipose tissue of untrained albino rats during two variations of predominant aerobic physical exercise: long-term swimming and long-term swimming including short-term loads (20 s) of maximal intensity (acceleration). Muscle and liver glycogen depletion, serum lactate, glucose and free fatty acids concentrations are also investigated. It is shown that long-term swimming (first variation) has promoted a decrease of both enzymatic activities in muscle fibres and an increase in lipolytic activity of the adipose tissue. During the physical exercise with the acceleration an increase in hexokinase activity occurs in response to 20 min swimming, with its maximal decrease in response to 40 min of exercise. Activity of lipase in slow-twitch oxidative fibres of soleus and in the adipose tissue increases from 20 min to the end of the exercise. Depletion of glycogen in the muscles and liver is determined in fast-twitch oxidative-glycolytic fibres and in the liver in two types of exercises, being more significant in muscles after exercise with accelerations. Concentrations of serum lactate, glucose and free fatty acids remain unchanged after both variations of swimming. So, it may be concluded that acute adaptation to the predominant aerobic physical exercise with activity under short-term loads of maximal intensity has induced a rise of the capacity of oxidative muscles to utilise endogenous and exogenous carbohydrate and lipid reserves.

[Utilization and restitution of energy sources during muscular activity under steady-state metabolic conditions]. / Utilizatsiia i restitutsiia istochnikov énergii pri myshechnoi deiatel'nosti v usloviiakh ustoichivogo sostoianiia metabolizma.

During muscular activity at steady state of metabolism both the carbohydrate and the free fatty acids are utilized as energy sources. Kreatine phosphate expense, carbohydrate mobilization, and intensity of glycolysis during the same work are in positive correlation with the work intensity, while fatty acids mobilization is in negative correlation. Intensity of restoration of energy sources is in positive correlation with the intensity of work and the energy source expense, while being in negative correlation with steady state level of metabolism. In trained organism, both the steady state level of metabolism during muscular activity and intensity of restitution during recovery period are greater than in untrained organism.

[Concentration of urea in blood and organs during muscular activity]. / Soderzhanie mocheviny v krovi i organakh pri myshechnoi deiatel'nosti

Muscular activity increases the content of urea in blood, liver, and muscles equally. The urea content in the kidney, however, either decreases or does not change at all, increasing only after an exhausting work or during the rest. The amount of protein in the diet influences upon the urea quantity in the organism, but the level of it's change under the action of muscular activity remains practically identical in the regime of the different protein nutrition. The activity of arginase in the liver and muscles is equally changed with the changes of the urea content in the blood and tissues.