Exercise Physiology PDF - Endocrine Response During Exercise

Exercise Physiology Endocrinal response & body weight during exercise DR. Nivin Sharawy Professor of Clinical Physiology User name: [email protected] Hormones & impact on 01 metabolism, heart, muscle...

Exercise Physiology Endocrinal response & body weight during exercise DR. Nivin Sharawy Professor of Clinical Physiology User name: [email protected] Hormones & impact on 01 metabolism, heart, muscle 02 Regulating Centers for food intake Short, intermediate & long regulation food intake 03 04 Obesity and exercise Insulin When exercise starts, the sympathetic nervous system suppresses the release of insulin It is important to avoid foods with high levels of sugar (including sports drinks) before exercise because it can elevate insulin levels and promote glycogen storage instead of allowing it to be used to fuel physical activity. Glucagon Released in response to low levels of blood sugar Glucagon is produced by the pancreas It stimulates the release of free fatty acids (FFAs) from adipose tissue and increase blood glucose levels, both of which are important for fuelling. As glycogen levels are depleted during exercise, glucagon releases additional glycogen stored in the liver. Diabetes and exercise Exercise benefits for individuals with diabetes Improved glycemic control (increased sensitivity of tissues to insulin so better uptake of glucose) Decreases cardiovascular risk factors Promotes weight loss Decreases anxiety levels Diabetes and exercise Guidelines for diabetic patient : Monitor blood glucose before, during, and after exercise Carbohydrate intake — Ingest 15-30 grams of CHO for each 30 min of intense exercise — Consume CHO snack after exercise Insulin Dose — Decrease insulin dose — Avoid exercising when insulin injection was given for 1 hour Avoid exercising in late evening Diabetes and exercise Exercise should be avoided in diabetics Blood glucose < 80 mg/dl Blood glucose > 250 mg/dl and urine ketones are present Cortisol & Thyroid hormones Cortisol is a steroid hormone produced by the adrenal gland in response to stress, low blood sugar and exercise. It supports energy metabolism during long periods of exercise by facilitating the breakdown of triglyceride and protein to create the glucose necessary to help fuel of exercise. Thyroxine (T4) & Triiodothyronine (T3) – stimulate metabolism and regulate cell growth and activity Epinephrine and Norepinephrine Help the sympathetic nervous system to produce energy during exercise. (breakdown of glycogen for energy and make lipolysis) Both hormones increase cardiac output, increase blood sugar (to help fuel exercise).  Testosterone & Growth Hormone Testosterone Muscle protein resynthesize Repair of muscle proteins damaged by exercise It increases red blood cells. Growth hormone Increasing muscle protein synthesis Increasing bone mineralization Supporting immune system function Promoting lipolysis. The body produces GH during high-intensity exercise such as heavy strength training. Growth hormone  Vasopressin (ADH) and aldosterone During exercise there is loss of fluids and electrolytes that is mediated by sweating as a result of increased body heat associated with exercise performance. The two hormones that responsible for stabilization of fluid and electrolyte balance in response to exercise ,they promote sodium, potassium, and water retention by the kidneys Endorphins β endorphin released as neurohormone from anterior pituitary to relieve pain and improve sense of well being during exercise It Increases with long-duration exercise. Endocrinal Response 2 Glucose: glucagon & insulin 2 metabolism: cortisol and thyroid hormones 2 metabolism & CVS : epinephrine & norepinephrine 2 muscle & bone: Testosterone and Growth hormone 2 Water maintenance: ADH & aldosterone Happy feeling: Endorphin  Control of Food Intake Regulating Centers for food intake: Present in the hypothalamus. These are: 1. The lateral nuclei (feeding center): Stimulation of this center results in increased food intake (hyperphagia), while its destruction causes marked weight loss. 2. The ventromedial nuclei (satiety center): Stimulation of this center causes complete satiety (aphagia), and its destruction leads to obesity. In addition, there are other centers : Paraventricular nuclei (PVN) which act to decrease food intake. Dorsomedial nuclei (DMN) which act to increase food intake. Arcuate nuclei which are the sites of action of gastrointestinal (as CCK and ghrelin) and adipose tissue hormones (as leptin) to regulate the food intake Factors that control the food intake: Short- term regulation: 1. Gastrointestinal filling and distension suppress the feeding center by stretch inhibitory signals transmitted via the vagi nerves 2. Oral factors as chewing, salivation, swallowing and tasting can affect the food intake. 3. Gut Theory which states that the GIT secretes polypeptide hormones that can affect the food intake.  Factors that control the food intake: Gastrointestinal hormones which decrease feeding as: Peptide YY (PPY) secreted especially from ileum and colon. It reaches a peak value 1-2 hours after meals. Its secretion depends on the food composition and increases in meals with high- fat content CCK which inhibit the feeding center. Glucagon-like peptide secreted from the intestine enhances glucose-dependent insulin production and secretion from pancreas. Gastrointestinal hormones which increase feeding: Ghrelin which is secreted mainly from the parietal cells of stomach and to a lesser extent from the intestines. It increases during fasting and stimulates feeding.  Factors that control the food intake: Intermediate and long- term regulation: Glucostatic theory of hunger and feeding: A rise in the blood glucose level increases the glucose utilization and the rate of firing of the glucosensitive neurons (Glucostats) in the satiety center. At the same time this increase in blood glucose inhibits the activity of glucosensitive neurons in the feeding center.  Factors that control the food intake: Intermediate and long- term regulation: Lipostatic theory: The hypothalamus is sensitive to the fat stores in the adipose tissue This is mediated by leptin which is secreted by adipocytes. Leptin crosses the blood-brain barrier by facilitated diffusion to reach its receptors in hypothalamus. Stimulation of leptin receptors results in multiple actions to decrease fat storage as follows: It increases sympathetic activity. Noradrenaline also binds to β3-adrenergic receptors on brown fat to stimulate production of uncoupled proteins resulting in release of large amounts of heat energy and little amount of ATP. Factors that control the food intake: Thermostatic theory: Exposure to cold weather results in increased food intake To increase the metabolic rate and thereby increases the heat production. To provide increased fat stores for insulation. This effect is due to interaction between food-regulating and temperature- regulating systems in the hypothalamus. Obesity and exercise Obesity: It is defined by an excess of body fat. It occurs when energy intake exceeds energy outcome. Body fat content can be measured by body mass index (BMI). It is calculated as follows: BMI = Weight in Kilograms / Height in square meter Values from 25-30 are overweight, and values above 30 are obese.  Obesity and exercise Causes of obesity: Decreased physical activity results in decreased muscle mass and increased body fat mass. Abnormal behavior of feeding (hyperphagia) related to environmental, social and psychological factors. Abnormalities in the neural pathways of the hypothalamus that control feeding. This leads to a higher ̔set- point ̓of feeding greater than in a non-obese person. Decreased sensitivity of feeding center to the inhibitory leptin signals, resulting in increased food intake. Genetic factors that may run in families. Endocrinal causes as in myxedema and Cushing syndrome. Sex: females are more susceptible to obesity more than males due to their lower muscle mass. Obesity and exercise Complications of obesity: Cardiovascular: Hypertension and increased incidence of atherosclerosis. Insulin resistance and development of type 2 diabetes mellitus Fatty liver and development of gall stones Osteoarthritis in the hip, knee and lumbar joints, and flat feet. Psychological problems.  Obesity and exercise Management of obesity: Producing a negative energy balance: Decreasing energy intake (restriction of food intake) Increasing energy expenditure (increasing physical activity and exercise). Drugs : Act centrally to decrease the degree of hunger Act peripherally to reduce lipid digestion and absorption. Surgical procedures: Gastric bypass Gastric banding Liposuction Obesity and exercise What kind of exercise do obese person need ? Walking Water aerobics Treadmill Key Points Hormones regulation during exercise: Glucose, stress, metabolism, fluid balance & muscle growth Food regulating centers Short, intermediate, long term regulation of food intake Obesity: Cause, complication & managements