Kidney Renal Activity

Background: During prolonged exercise of a sub maximal intensity, the body becomes hot due to an increase in muscle contractions. In response to this, sweating occurs and evaporates from the skin resulting in an increase in water and sodium loss from the body. To counteract this process, the kidney has evolved a control mechanism whereby water and sodium is conserved and the kidneys decrease the rate of urine production. When water is ingested it is rapidly absorbed by the intestine diluting the blood. This is detected by osmoreceptors in the hypothalamus which reduces the anti-diuretic hormone, ADH, by the pituitary gland. The kidneys respond to this drop in hormone by increasing the production of urine i.e. les water is reabsorbed.

Aims: The main aim of this experiment was to investigate the interaction between water consumption and prolonged sub maximal exercise on kidney function. The main observations of the study focused on changes in urine production and its pH, osmolality, Na+ and K+ content alongside changes in skin and core body temperature.

Methods: 80 ppts in groups of 4 were divided into 2 subjects and 2 experimenters. Subjects then allocated exercise or control condition. It was important that subjects came to the lab in a normally hydrated state. All subjects were then given a code letter to label urine samples with. Both control and exercise Subjects emptied their bladders before ingesting 1000mls (1 litre) of water at which the time was noted. Non-clothed weights were recorded immediately and repeated after 1 hour and 2 hours. The control and exercise subjects produced urine samples every 20mins for the next 2 hours. The exercise subject took part in 1 hour of sub maximal intensity exercise on a cycle ergometer ( suggested workloads being 120 watts for females and 150 to 180 watts for males) followed by a 1 hour recovery period. Skin temperature at the surface of the thigh and aural temperature (indicator of core temperature) were taken...