University:
California State University, Northridge
Course:
FCS 481 | Sports Nutrition
Academic year:

2009
Views:

308

Pages:

17
Author:

Zoey Chang

Protein & Exercise The Importance of Protein Composed of C, H, O, N  Primary structural material  Many physiological roles in the body  Crucial due to amino acid components   Needed for synthesis of various body proteins & nitrogen molecules  9 Essential  11 Nonessential 1 Protein Needs  Current Normal Adult RDA: 0.8 g/kg/day  Scientific data suggests certain athletes may need more  Endurance: 1.2 – 1.4 g/kg/day  Strength: 1.2 – 1.7 g/kg/day Protein & Exercise   Protein is the “Third Choice of Fuel” Athletes are concerned with:  What type of protein  Food, protein powders, amino acid mixtures  BCAA’s: main amino acids oxidized for energy, role in muscle building  When to eat protein  1 – 2 hours after training session  Enhance anabolic processes in muscle  How much to eat  Endurance & Strength Athletes 2 Biochemistry of Protein Digestion  Absorption  Metabolism  Excretion  Protein Digestion  Stomach ○ HCL denatures protein structure ○ Activation of pepsinogen to pepsin ○ Pepsin hydrolyzes peptide bonds in protein/ polypeptides  In Small Intestine ○ Acid chyme stimulates release of regulatory hormones and peptides (secretin and cholecystokinin) ○ Zymogens secreted by the pancreas further responsible for protein and polypeptide digestion. ○ Peptidases enable peptide digestion and amino acid absorption in the distal small intestine. 3 Protein Absorption  Occurs in Small Intes0ne  most in the proximal small intes0ne Carriers required; paracellular absorp0on can also occur  In general   BCAA absorbed faster than smaller amino acids  Neutral AA ↑ rates of absorp0on dibasic and dicarboxylic AA  EAA absorbed faster than NEAA  Over 60% of amino acids are absorbed in the form of small pep0des. Protein Metabolism Anabolism: building up of tissue proteins  Catabolism: breaking down proteins   For energy Dependent on nutritional status of the individual  Need enough of all essential amino acids (EAAs) in the diet   Primary source of EAAs  If exogenous protein supply is low  fasting or starvation  degradation occurs to provide energy 4 Protein Metabolism  Liver Primary site for the uptake of most (50%-65%) amino acids (AAs)  Regulates absorbed AAs and adjusts the rate of metabolism according to needs  Exception- branched-chain amino acids (BCAAs)  BCAAs are more rapidly metabolized in muscles and adipose tissue Protein Metabolism       BCAAs that arrive at the muscles  Important to exercise and sport Following a meal with protein, AAs usually in excess  Skeletal muscle typically experiences protein synthesis Fasting or strenuous exercise  muscle breaks down protein to AAs Nitrogen (N) transported through the bloodstream and liver in transamination and deamination processes  Alanine-glucose cycle Results in synthesized glucose Transported back to the muscle and used for energy 5 Protein Excretion  Ammonia produced from oxidation is toxic  Accumulation can quickly cause death  Must be safely removed from the body  Urea cycle (ornithine cycle):  Removes ammonia by converting to urea  Takes place in the liver Urea, which is water soluble, is transported to the kidneys and is readily excreted  Healthy individuals with appropriate protein intake urinary urea N represents approximately 80% of all urinary N  Protein Excess Increased calcium excretion  Decreased kidney function  Edema  Liver dysfunction  Vitamin B6 deficiency  Dehydration  Coronary Artery Disease  Build up of Ketones  6 Protein Deficiency  Increased intestinal permeability  Edema  Anemia  Muscle atrophy  Vitamin A deficiency What Current Research Studies Indicates…. Endurance Exercise • Carbohydrates & Endurance Exercise • Strength/Power Athletes • Supplements • 7 Protein & Endurance Exercise Branched-Chain Amino Acids Activate Key Enzymes in Protein Synthesis after Physical Exercise 8 Purpose  The purpose of this study was to review if BCAA’s have anabolic effects on protein metabolism by increasing protein synthesis and decreasing the rate of protein degradation in resting muscle. It also wanted to see what effect resistance exercise had on protein synthesis vs. endurance exercise. Methods  Study was more of a review of articles comparing the effects of exercise on protein synthesis 9 Conclusion The article reviews suggested that an increased availability of BCAAs stimulates translation of specific mRNAs in muscle during recovery of resistance exercise.  There is a lack of data to see the relationship of BCAA and endurance exercise.  Evaluation (+) (-)  Compared multiple  Review of studies so studies (makes the subject and theory more reliable) there was no real protocol, methods, etc.  Not enough information on endurance exercise and its relationship with protein synthesis. 10 Protein, Carbohydrates & Endurance Exercise Carbohydrate and protein hydrolysate coingestion’s improvement of lateexercise time-trial performance 11 Purpose  Primary Purpose: to determine whether a CHO and protein hydrolysate (ProH) beverage would bring out improvements in performance during time-trial cycling versus a CHO beverage alone.  Secondary purpose: to determine whether treatment with CHO+ProH lessened signs of muscle disruption as compared with CHO. Methods  Randomly counterbalanced double-blind design  13 recreationally competitive male cyclists  either a CHO+ProH beverage or CHO beverage  2 computer simulated 60 km time trials  Participants with 2 or more risk factors for coronary artery disease were excluded 12 Measurements        VO2 max respiratory exchange rate (RER) ratings of perceived exertion (RPEs) blood glucose heart rate lactate Plasma creatine phosphokinas (CK) and muscle soreness ratings were assessed before and after 24 hours Results  CHO+ProH beverage improved time-trial performance  All occurring in the final lap (late stage) of the test  Plasma CK and muscle soreness ratings were high in the CHO trial, but not with CHO+ProH 13 Implication  Addition of ProH to the CHO drink may have prolonged the time to muscle fatigue.  ProH may have reduced markers of muscle disruption Evaluation (+)       Adequate background information and review of related literature. Previous studies ambiguous and did not examine differences of late stages Design strong enough to address previous ambiguities explanation of protein hydrolysates Conclusion valid Results supported ProH use (-) Use of more references, including contrasting literature  Small sample size of 13  Need larger sample for more accurate results  Can not be generalized to all athletes, only:  Males  Endurance cyclists  14 Resistance Exercise Increase Postprandial Muscle Protein Synthesis in Humans Purpose The purpose of this study was to examine the impact of acute bouts of resistancetype exercise on muscle protein synthesis in the fed state. 15 Methods-Subjects  10 untrained males  No history of participating in any regular exercise program and were asked to refrain from heavy physical exercise and stay on a normal diet for 3 days during the experiment.  Body comp was assessed  Subjects single leg on rep max was determined Methods-Protocol       Consumed meal night before experiment (55% carbohydrate, 25% protein, 30% fat) Breakfast (52% carbohydrate, 34% protein, 4% fat) Subjects rested supine 1 hour before exercise. 5 min warm-up on bike Unilateral lower limb exercises Arterial blood and muscle biopsies were obtained from the vastus lateralis of the exercised and non exercised leg after 45 min programs were complete. 16 Results Plasma insulin, glucose, phenylalanine, and BCAA concentrations reached maximal levels after cessation of exercise and returned to normal after 2-4hrs.  Phenylalanine levels were significantly higher in the exercised leg  Muscle protein synthesis is stimulated sooner in the exercised leg  Conclusion (+)  Tested exercised vs unexercised on same body so it was more accurately comparable  Regulated diet  That correct diet and exercises did positively effect protein synthesis (-)  Small number of subjects  Only tested untrained individuals  Only males  Only in fed state 17

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