Proteins, amino acids and exercise Proteins and amino acids n Proteins n the most important biological compounds needed for life n act as the structural materials in humans n Enzymes are proteins that catalyze the body's chemical reactions. n make up muscles that aid in movement. n Amino acids n Proteins are made up of chains of amino acids. n an amine group (-NH[2]) bonded to a carbon atom that is bonded to a carboxylic acid group (-COOH) Amino acids can bond together by peptide bond Amino acids (AA) n 20 amino acids in the nature n Classification of amino acids n Essential AA - methionine, leucine, isoleucine, lysine, phenylalanine, threonine, tryptophan, and valine n Conditionally essential AA - histidine, arginine (required for infants) n Nonesential AA – glycine, aspartic acid, asparagine, proline, glutamine, glutamic acid, cysteine, tyrosine, serine, alanine, hydroxyproline Digestion and absorption of protein n Digestion n The stomach n Hydrochloric acid, pepsine n Proteins => polypetides, amino acids n The small intestine n pancreatic and intestinal proteases n Polypeptide => oligopeptides, tripeptides, dipeptides, amino acids n Peptidase n Tripeptides and dipeptides => amino acids n Absorption n Specific carriers transport AA Roles of proteins in the body n As a building material n As enzymes n As hormones n As regulator of fluid balance n As acid-base regulators n As transporters n As antibodies n As a source of energy and glucose Protein metabolism n Protein turnover and the amino acid pool n proteins are being made and broken down n Nitrogen balance n Positive – growing infants, childrens, pregnant women n Negative – people who are starving or suffering severe stress n Using AA to make proteins, nonessential AA n Using AA to make other compounds n Tyrosine → neurotransmitters - norepinephrine, pigment melanin, hormon thyroxin, precursor for the vitamin niacin Proteins in food and their quality n Source of protein n Animal source – meat, fish, milk and dairy products, egg n Plant source – lentils, legumes, nuts, whole grains, vegetables n Limiting AA n e.g. lysine in grains, methionine in legumes n Complete protein = animal protein – contains all esential AA n Biological value (BV) n A measure of protein quality n The amount of protein nitrogen that is retained from a given amount of protein nitrogen absorbed n BV egg 100, meat 92 – 92, fish 94-96, legumes 75-80, grains 70 RDA of protein n 12 – 15 % energy n Diet 2000 kcal = 300 kcal from protein = 75 g Approximate protein content of various foods Metabolism of amino acids and protein during exercise n Amino acid x not source of energy n Hormones influence muscle protein turnover n Influence synthesis, breakdown or both n Anabolic - synthesis n Catabolic – breakdown n Single exercise bout modify the amount of circulating levels of hormones n Growth hormone, tyrosin ↑ Hormones influence muscle protein turnover n Insulin n Release is stimulated by elevated blod glucose and less potently by elevation of AA n Promote uptake of AA to cells (skeletal muscle) n Promote a synthesis of protein, limiting break down n During exercise is release of insulin blunted (greater glycogen and fat breakdown) n Endurance exercise - more AA available for gluconeogenesis Hormones influence muscle protein turnover n Cortisol n Released by the adrenal gland during physiological or nutritional stress n Stress hormone n Increase energy nutrient availaility – breakdown protein n Vary in level during exercise (intensity, duration) n Growth hormone (GH) n Increase during exercise, remain elevated for some time afterward n Increase level of AA after protein rich meal => ↑ GH n ↑ GH => ↑ AA uptake to muscle cells, protein synthesis Hormones influence muscle protein turnover n Insuline-like growth factor 1 (IGF-1) n Anabolic efect of GH is mediated with IGF-1 n If IGF-1 is ↓ and GH is ↑ = inhibited protein synthesis n Testosterone n Promoter of protein synthesis in muscle n Enhance utilization of AA for protein synthesis n Level of testosterone ↑ = resistance and endurance training Resistance exercise (RE) n Protein synthesis n unchanged or reduced during RE n Increase for several hours after RE n Protein breakdown n Not occur during RE n May increase after RE n AA oxidation n Not enhanced during RE n Consumption of a carbohydrate and protein meal after RE => minimize protein breakdown => maximize protein synthesis Endurance exercise (EE) n Protein synthesis n unchanged or reduced during EE n Protein breakdown n can occur during higher intensity, longer duration EE n AA oxidation n Can occur during prolonged moderate to higher intensity submaximal EE n Consumption of carbohydrate and protein meal after EE => minimize protein breakdown => maximize protein synthesis Protein intake of athletes n Endurance athlete 1,2 - 1,4 g/kg n Strength athlete 1,4 – 1,8 g/kg n Timing and composition of meal - postexercise n Carbohydrates – fuel and increase the uptake of AA n AA – allows for an influx into muscle cells, protein synthesis n After training n 0,5 g protein per kg + 1,5 g carbohydrates per kg n Weight training - at lest 135 g of carb. and 45 g of protein for a 90 kg weight trainer n Endurance training – at least 105 g of carb. and 35 g of protein for a 73 kg endurance athlete = 560 – 720 kcal (1/5 – 1/6 daily energy needs) n After 3-4hour eat again => Maximise positive efect of exercise on muscle protein turnover Protein intake of athletes n Timing and composition of meal – during exercise n Carbohydrate consumption (e.g. Sport drinks) – support better recovery and adaptation n Number of meals n Numerous smaller meals over the waking hours = more consistent influence on insulin level = minimize catabolic periods between meals = more consistent availability essential AA = more desirable influence on protein synthesis n 5 – 6 meal during a day n After exercise approximately 40 g protein n Each other meal 15 – 20 g of protein