What are the Fuels the Body Uses for Activities? Table 14-3, p. 485 Reviewing Aerobic Metabolism 1
Features of Aerobic Exercise Uses oxygen in the generation of energy Low intensity, long duration activity Builds endurance Uses primarily fat as the primary energy source Examples of Aerobic Activities Abundant energy from the breakdown of fat can come only from aerobic metabolism. 2
Reviewing Anaerobic Metabolism Features of Anaerobic Exercise No oxygen used in the generation of energy High intensity, short duration activity Builds strength and bulk of muscles Uses primarily carbohydrate as the primary energy source Split-second surges of power as in the heave of a barbell or jump of a basketball player involve anaerobic work. 3
Recycling of Glucose Production of Lactic Acid Energy Fuels The proportion of carbohydrate, fat and protein used for energy depends on a number of factors: diet intensity & duration of activity training Glucose Use during 1. High carbohydrate intake increases glycogen storage, increasing endurance time. 4
Glucose Use during (2) 2. Intensity of activity affects glycogen use: Moderate activities use it slowly Intense activities use it quickly Glucose Use during 3. Duration of activity affects glycogen use: First 20 minutes of activity primarily uses glycogen After 20 minutes, both glycogen and fat used Glucose Use Fat and protein diet Normal mixed diet High-carbohydrate diet Maximum endurance time: 57 min 114 min 167 min Diet affects glycogen storage and use Fig. 14-3, p. 486 5
Maximizing Glucose Supply High-carb diet: 8 g/kg body weight or 70% of total energy intake Glucose during activities if activity lasts longer than 1 hour (sports drinks, diluted juice) Eat approximately 60 g high-carb foods after activity Glycogen Loading Glucose After Activity High-carb meal within 15 minutes accelerates glycogen storage by 300% High-carb meal within 2 hours: rate of glycogen storage declines by half 6
Glucose After Activity (2) High-glycemic index foods may be more beneficial to those wanting to maximize muscle glycogen synthesis Training Affects Glucose Use Trained muscles will store more glycogen. Conditioned muscles rely less on glycogen and more on fat for energy: Have more mitochondria Can use oxygen better Training Affects Glucose Use (2) Untrained muscles depend more heavily on anaerobic pathways 7
Fat Use During Duration of activity affects fat use: Beginning of activity uses fatty acids in blood Body fat used after 20 minutes of activity Fat Use During Intensity of activity affects fat use: As intensity increases, fat contributes less to fuel mix Oxygen must be abundant to metabolize fat. Training Affects Fat Use The better trained the muscles, the more fat is used The better trained, the stronger the heart and lungs to deliver oxygen 8
Training Affects Fat Use In the better trained, hormones slow down the release of glucose from liver cells, so they burn more fat for energy. Protein in Muscle Building Synthesis of body protein suppressed during activity After activity, protein synthesis accelerated Protein Use During Diet affects protein use during activity: Diets rich in energy and carbs use less protein for energy Carbohydrates spare protein 9
Protein Use During Intensity and duration of activity affects protein use: If glycogen stores are depleted, then more reliance on protein for energy Protein Use During (2) Intensity and duration of activity affects protein use: Anaerobic strength training demands some more protein to build muscle, but not large amounts Protein Use During (3) Training affects protein use: The better trained the muscles, the less protein is used for energy 10
Table 14-4, p. 491 To learn more about coming diet and fitness trends, please visit the following website. http://www.webmd.com/diet/features /diet-and-fitness-trends?page=1 11