Week 3 - CHO for sport and exercise Student PDF

Carbohydrates Dr Joel Craddock [email protected]...

Carbohydrates Dr Joel Craddock [email protected] 1 1 Lecture Outcomes By the end of this lecture, you should be able to: Classify carbohydrates according to their chemical composition. Describe the digestion and absorption of carbohydrates. Explain the metabolism of glucose. Describe how muscle glycogen and blood glucose are used to fuel exercise. Detail and explain carbohydrate recommendations for athletes, including specific guidelines for intake before, during, and after exercise. Describe how carbohydrate periodisation could be used to optimise exercise performance Determine the daily carbohydrate needs of an athlete, and select carbohydrate-containing foods to meet the recommended intake. 2 2 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 1  Carbohydrates in Food 3 3 Carbohydrates in Food Monosaccharides Disaccharides Polysaccharides 4 4 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 2  Characteristics of Monosaccharides Chemical name Sweetness (100 = Glycemic index Miscellaneous information Sweetness of table (based on 100) sugar) Glucose 75 100 In the body, found circulating in the blood and stored as glycogen. In food, generally found as part of disaccharides and polysaccharides (starches). When added to food, glucose is referred to as dextrose. Fructose 170 19 In the body, found temporarily in the liver before being converted to glucose. In food, found naturally in fruits and vegetables and added to processed foods, often as high-fructose corn syrup. Galactose 30 Unknown Found in food only as part of lactose. 5 5 Chemical Structure of Monosaccharides 6 6 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 3  Characteristics of Disaccharides Chemical name Monosaccharide Sweetness Glycemic Miscellaneous information composition (100 = sweetness index of table sugar) (based on 100) Sucrose Glucose + fructose 100 68 Found in fruits, vegetables, honey, and maple syrup; sugar beets and sugar cane are processed into white and brown sugar. Lactose Glucose + galactose 15 46 Most adults lose their ability to digest lactose (milk sugar). Maltose Glucose + glucose 40 105 Minor disaccharide in most diets. 7 7 Chemical Structure of Disaccharides 8 8 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 4  Polysaccharides Starch − Amylopectin − Amylose Glycogen Fiber − E.g. Cellulose 9 9 Polysaccharides 10 10 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 5  Classifying Carbohydrates There is no single way to classify carbohydrates Sugars and starches Simple and complex Minimally processed (“quality”) vs. highly processed “Good” vs. “bad” 11 11 Document title 12 Whole vs Refined 12 12 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 6  Digestion, Absorption, and Transportation of Carbohydrates 13 13 The Human Digestive Tract 14 14 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 7  The Human Digestive Tract - CHO 15 15 The Structure of the Small Intestine 16 16 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 8  Carbohydrate Digestion and Absorption 17 17 Metabolism of Glucose in the Body 18 18 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 9  Glucose Metabolism Involves many metabolic pathways, which include: The regulation of blood glucose concentration The immediate use of glucose for energy The storage of glucose as glycogen The use of excess glucose for fatty acid synthesis The production of glucose from lactate, amino acids, or glycerol 19 19 Regulation of Blood Glucose 20 20 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 10  Regulation of Blood Glucose 21 21 Glycemic Response 22 22 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 11  Survey Activity 2 All of these foods contain carbohydrates, but they each have a different effect on blood glucose. Why is this? How might this affect an athlete’s carbohydrates choices? 23 23 Metabolism of Carbohydrate Once in cell glucose can be used immediately or stored for later use − Depending on requirements How glucose is metabolised depends on several factors − Cell type i.e. Red blood cells vs heart cells or slow twitch muscle fibre − Enzymatic ability of cell − Energy state i.e. glycogen status − Hormonal status − Training hx − Intensity of exercise i.e. aerobically or anaerobically 24 24 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 12  Metabolism of Carbohydrate 25 25 Carbohydrates as a Source of Energy for Exercise 26 26 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 13  Use of Muscle Glycogen During Exercise 27 27 Use of Muscle Glycogen During Exercise The effect of different exercise intensities (lines on the same graph) and different baseline muscle glycogen (individual graphs) on muscle glycogen utilisation Muscle glycogen use increases with the intensity of exercise Fatigue at high intensity exercise levels (100 & 130% VO2max) aren’t associated with low muscle glycogen stores At 70% VO2max the point of fatigue is associated with low muscle glycogen stores. In Figure c., when starting muscle glycogen stores are highest – time to exhaustion @ 70% VO2max is extended in comparison to Figures a. and b., where starting muscle glycogen stores are lower. Of note, an important adaptation to endurance training is the increased ability to store carbohydrate (glycogen) in the muscle. Note time to fatigue only estimated in 70% VO2max Figure: Predicted skeletal muscle glycogen in vastus lateralis during continuous cycling exercise at four exercise intensities (40, 70, 100 & 130% VO2max) for males with a VO2max of 60 ml/kg/min and different baseline (starting) muscle glycogen: a 400, b 600 and c 800 mmol/kg DM). Timepoints are 0, 4.7, 22.7, 53.5 and 116 min, nudged for enhanced visualisation. The grey-shaded timepoints at 70% VO2max represents time to fatigue. Error bars are 90% confidence limits. 28 28 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 14  Muscle Glycogen Content Muscle glycogen content varies depending on both diet and training status A trained athlete has a greater capacity for glycogen storage CHO further enhanced by a high carbohydrate intake Dictates CHO fuelling strategies i.e. more aggressive CHO intake leading into an endurance event in well trained athletes Predicted resting glycogen concentration in vastus lateralis of males with VO2max of 40–70mL/kg/min in conditions of low, normal and high Areta J. & Hopkins W.G (2018). carbohydrate availability. 29 29 Glycogen Use in Different Sports Starting glycogen conc depends principally on 1) training status + pre-exercise dietary CHO intake Figure credit SDA 30 30 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 15  Carbohydrate Oxidation Rates Multiple factors influence CHO oxidation rates. Two main ones Total energy expenditure (TEE) − Exercise intensity and body mass Proportion of energy from CHO − Acute CHO availability i.e. fed vs fasted − Habitual CHO intake i.e. high vs low CHO − Training status − Exercise intensity Can be determined in lab looking at RER CO2 output vs O2 intake 31 31 Respiratory Exchange Ratio and Energy Percentages from Carbohydrates and Fats RER Percent CHO Percent fat 1.00 100 0 0.95 83 17 0.90 66 34 0.85 49 51 0.80 32 68 0.75 15 85 0.70 0 100 RER = respiratory exchange ratio; CHO = carbohydrate The RER calculated from measured VO ̇ 2 and VCO ̇ 2 can be used to determine the percentage of energy that is being derived from carbohydrate and fat oxidation. The full table can be seen in Appendix H. Source: Carpenter, T. M. (1964). Tables, factors, and formulas for computing respiratory exchange and biological transformations of energy (4th ed., p. 104). Washington, DC: Carnegie Institution of Washington. 32 32 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 16  Muscle Glycogen Use and Carbohydrate Consumption During Exercise 33 33 High carbohydrate availability - Acute High carbohydrate availability in an acute exercise setting can be achieved by: Deliberately elevating pre-exercise muscle glycogen stores Consuming a carbohydrate rich pre- exercise meal Consuming carbohydrate during exercise Research consistently shows that exercise with high CHO availability improves acute exercise performance compared to exercising in a state of lower carbohydrate availability (i.e. fasted). Overview of all studies examining carbohydrate (CHO) intake and exercise performance versus a noncaloric placebo. Data represents studies undertaking time trial (TT) protocols only, with all time to exhaustion trials omitted. Stellingwerff T. & Cox GR (2014). 34 34 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 17  High Carbohydrate Availability - Chronic Study Achten et al (2004) Runners undertook an 11-day training block, whilst consuming either 5.4 or 8.5 g/kg/day CHO. On days 1, 5, 8 and 11 runners completed a laboratory performance test, with easy training on days 2,3 and 4, and hard training days on days 6, 7, 9, and 10 Achten J. et al. Higher dietary carbohydrate content during intensified running training results in better maintenance of performance and mood state. J Appl Physiol. 2004; 96(4):1331– 1340. 35 35 High Carbohydrate Availability - Chronic Study Achten et al (2004) 36 36 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 18  Low CHO availability - LCHF Diets for Athletes Not new, but social media ⬆ Upregulation of fat oxidisation + shift point of fatmax to higher % VO2max Generally endurance focused with several theories on benefits − Muscle glycogen limited – fat is just about unlimited − Less CHO during activity required − Fat as a substrate produces more energy/gram > weight efficient fuel source − Can train at lower CHO intake without training compromise and could be beneficial for reducing body weight/fat 37 37 LCHF Diets for Athletes HC: n=10, % carbohydrate:protein:fat = 59:14:25 LC: n=10, % carbohydrate:protein:fat = 10:19:70 Diet for an average of 20 months Fig. Fat (A) and carbohydrate (B) oxidation rate during 180 min of running at 64% VO2 max and 120 min of recovery. All time points were significantly different between groups. LC = low-carbohydrate diet group; HC = high-carbohydrate diet group. Volek et al 2015. 38 38 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 19  Carbohydrate availability - Glycogen Threshold Hypothesis Metabolic adaptations occur within skeletal muscle in highly trained athletes at submaximal work rates. increased capillarisation mitochondrial density mitochondrial number enhanced activity of mitochondrial enzymes such as 3-hydroxyacyl-CoA dehydrogenase (HAD) and citrate synthase (CS) enhanced lactate oxidisation increased concentration of transport proteins glycogen concentration ability to metabolise fat as a substrate Training with low carbohydrate availability enhances the metabolic adaptation to exercise Research suggests that it is the post-exercise glycogen concentration that influences the level of adaptation that occurs coined ‘glycogen threshold hypothesis’. To maximise training adaptations, the post-exercise muscle glycogen concentration should be below a "threshold" value, proposed to be ~ 300mmol/dry wt. muscle 39 39 Low CHO Availability Strategies Instead of following a LCHF diet other nutritional strategies could be employed − Training fasted − No CHO during training − Delayed rescue (no CHO post training) − Training twice daily second session no CHO − Sleep low 40 40 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 20  Carbohydrates and gut training 41 41 Carbohydrate availability + gut training Training with high carbohydrate availability ensures athletes are prepared for competition. − Particularly important if significant carbohydrate intake is required during their competitive event. Gut training crucial for several reasons: To ensure the athlete is familiar with the sports foods and drinks they will consume taste storage/carrying items open the packaging consume them safely and confidently To ensure the athlete is familiar with the timing and quantities To ensure the athlete's gastrointestinal tolerance of the planned food and fluids is sufficient to ensure adequate digestion and absorption (and minimise GI symptoms) during competition. 42 42 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 21  Gut training – Costa et al (2017) Study Endurance runners completed a "gut challenge", 2 hours treadmill running at 60% VO2max whilst consuming 90g/hr of carbohydrate (glucose/fructose mix). Immediately followed by a 1-hour distance trial, where participants ran as far as possible in 1 hour. Gut training consisted of 2 weeks of training 5 days/wk, 1 hour run, randomly assigned to consume 90g CHO from either gels or food, or a placebo gel. The gut challenge and performance test was then repeated following gut training. 43 43 Gut training – Costa et al Study 44 44 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 22  Gut training – Costa et al Study Summary After 2 weeks of gut training, runners randomised to CHO during training (both gels and food) improved distance trial performance by around 500 meters − No improvement in the placebo group. Total and upper GI symptoms were significantly reduced in the CHO groups, with no change in the placebo group. Lab 2 related to this study 45 45 Gut Training Implementation Currently no consensus or published guidelines Possible strategies Undertake training sessions with the target amount of carbohydrate at least 1-2 times a week. § If rapid gut training is required, more frequent sessions may be required. − Gut Challenge § If oxidation rate testing is available, a gut challenge can be undertaken. § At race pace, feed 90g/hr, measuring oxidation rate every 30min for 2-3 hours (endurance athletes only). If CHO oxidation is poor (e.g.