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The Scientific Basis of Aerobic Fitness

The Scientific Basis of Aerobic Fitness. Chapter 3. PE 254. Overview of Energy Metabolism. large nutrients digested into smaller, usable fuels carbohydrates  glucose fats ( triglycerides )  fatty acids proteins  amino acids

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The Scientific Basis of Aerobic Fitness

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  1. The Scientific Basis of Aerobic Fitness Chapter 3 PE 254

  2. Overview of Energy Metabolism large nutrients digested into smaller, usable fuels carbohydrates  glucose fats (triglycerides)  fatty acids proteins  amino acids blood delivers fuels to muscle which transforms them into ATP (adenosine triphosphate) ATP is the universal “currency” used by tissues for energy needs food + O2  ATP + CO2 + H2O + heat

  3. Energy Systems: Fuels Carbohydrates primary form is glucose transported to muscle (and other tissues) via blood stored in liver and muscle as glycogen ATP produced more quickly from CHO than from fats or proteins CHO stores can be depleted

  4. Energy Systems: Fuels Fats (triglycerides) stored in adipose tissue and in muscle muscle uses fatty acids for fuel produce ATP more slowly than CHO during rest, provides >½ the ATP, but little during intense exercise fat stores not depletable

  5. Energy Systems: Fuels Proteins split into amino acids in gut, absorbed, and transported by blood primary role is providing building blocks for metabolic functions and tissue building provides 5-15% of fuel for ATP production

  6. Overview of Energy Metabolism muscles have small ATP storage capacity 3 energy systems produce ATP aerobic – primary system for endurance events anaerobic – primary system for speed events “immediate” – primary system for power events systems may work simultaneously depends upon exercise intensity and duration

  7. Interaction of Energy Systems Aerobic system takes 2-3 min to fully activate Anaerobic system takes ~5 s to fully activate Immediate system can provide ATP immediately

  8. Exercise Energy Metabolism During Exercise At onset of exercise, three systems are used continuously, though contribution of the three systems change with time.

  9. Aerobic Capacity • Ability of the Cardiovascular system to deliver oxygen rich blood to body tissues. • Muscles ability to process and utilize oxygen to produce energy.

  10. Evaluating Aerobic Capacity • Measure • VO2max via spirometry / graded exercise stress test • Estimate • Sub-maximal graded exercise test • Step test • Based on the fact that individuals with higher SV will recover faster • Recovery HR will be lower in individuals w/ higher VO2max

  11. Heart Rate Response to Step Test

  12. Factors That Effect Aerobic Conditioning • Initial level of cardiovascular fitness • Frequency of training • Duration of training • Intensity of training • Specificity of training

  13. Initial Fitness Level • Lower initial fitness level allows more room for improvement • Generally “average” individual can expect 5-25% improvement w/ 12 weeks of training • Everyone has GENETIC Limit • Some people are genetically more gifted and/or respond better to training

  14. Frequency of Training • Generally recommended: at least 3 X’s/week • Training 4 or more days per week results in only small increases in VO2max • Weight control: 6 or 7 days/week recommended

  15. Continuous vs. Discontinuous Exercise • Continuous (Long Slow Distance) • 70-90% of HR max • Less taxing on individual • Interval Training • Repetitive exercise intervals separated by rest intervals • Exercise Interval: 90% HR max • Rest interval: 3X’s as long as exercise (3:1 ratio)

  16. Training Intensity • Most critical factor in training • May be expressed as: • % of VO2max • Heart rate or % of maximum HR • METS (metabolic equivalents) • Rating of Perceived Exertion (RPE) • Calories per unit time

  17. Training Intensity • Threshold for aerobic improvement • At least 50-55% of VO2max • 70%+ of age predicted max HR (220-age) • Often referred to as “conversational exercise” • Overload will eventually become average activity • Must increase intensity / duration to continue improvement in CV endurance

  18. ACSM Recommendations • At least 3X’s per week • 30 – 60 minutes • Continuous, large muscle mass exercises • Expend at least 300kcals per session • 70% of age predicted max HR

  19. Guidelines • Start slowly • Much higher risk of injury before adaptation occurs • Warm Up (50-60% Max HR) •  temp. of & blood flow to muscle • Gentle stretching • Dress for the weather • Cool Down • Increases lactic acid removal • Gentle stretching

  20. Lactic Acid – anaerobic breakdownproduct of pyruvate • Fatigue • Predominates at higher intensities – less able to clear • With improved fitness – better able to tolerate lactic acid build up

  21. Basal Metabolic Rate Your basal metabolic rate, or BMR, is the minimum calorific requirement needed to sustain life in a resting individual. It can be looked at as being the amount of energy (measured in calories) expended by the body to remain in bed asleep all day! BMR can be responsible for burning up to 70% of the total calories expended, but this figure varies due to different factors (see below). Calories are burned by bodily processes such as respiration, the pumping of blood around the body and maintenance of body temperature. Obviously the body will burn more calories on top of those burned due to BMR.

  22. Components of Daily Energy Expenditure Thermic effect of feeding Energy expenditure of physical activity Resting energy expenditure 8% 17% 8% 32% 75% 60% Sedentary Person (1800 kcal/d) Physically Active Person (2200 kcal/d) Segal KR et al. Am J Clin Nutr. 1984;40:995-1000. Slide Source: www.obesityonline.org

  23. Energy needed for activity • Calorimetry gives energy needed for various levels of activity. Energy expenditures above basal: • Eating, reading 0.4 Cal/kg-h • Doing laundry 1.3 • Cello playing 1.3 • Walking slowly 2.0 • Walking 4 mph 3.4 • Swimming 2 mph 7.9 • Crew race 16.0

  24. Basal metabolic rate • It takes energy just to stay alive. • Basal metabolic rate, or BMR • For warm-blooded animals, most energy used • to maintain body temperature. • Human BMR: 1.0 Cal/kg-h • Example: m = 70 kg, 24 hour day • Basal metabolism = 1.0 Cal/kg-h * 70 kg * 24 h/day • =1680 Cal/day • This does not account for any activity.

  25. Figuring total caloric needs: One 75 kg person’s day Basal metabolism 1.0 Cal/kg-h * 24 h * 75 kg = 1800 Cal Reading, writing, talking, eating, 12.5 h 0.4 Cal/kg-h * 12.5 h * 75 kg = 375 Cal Walking slowly, 1 h 2.0 Cal/kg-h * 1 h * 75 kg = 150 Cal Playing cello, 1.25 h 1.3 Cal/kg-h * 1.25 h * 75 kg = 120 Cal Energy needed for digestion 2500 Cal consumed * 8% = 200 Cal Total needs: 2645 Cal

  26. Total daily energy expenditure Solving for moderate exercise activity total daily energy expenditure (TDEE) TDEE (moderate) = 1.55 x BMR

  27. Harris-Benedict Men: BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) - (6.8 X age) Women: BMR = 655 + (9.6 X wt in kg) + (1.8 X ht in cm) - (4.7 X age) Note: 1 inch = 2.54 cm.1 kilogram = 2.2 lbs. Example: You are femaleYou are 30 yrs oldYou are 5' 6 " tall (167.6 cm)You weigh 120 lbs. (54.5 kg)Your BMR = 655 + 523 + 302 - 141 = 1339 calories/day

  28. Activity multiplier Sedentary = BMR X 1.2 (little or no exercise, desk job)Lightly active = BMR X 1.375 (light exercise/sports 1-3 days/wk)Mod. active = BMR X 1.55 (moderate exercise/sports 3-5 days/wk)Very active = BMR X 1.725 (hard exercise/sports 6-7 days/wk)Extr. active = BMR X 1.9 (hard daily exercise/sports & physical job or 2X day training, i.e marathon, contest etc.) Example: Your BMR is 1339 calories per dayYour activity level is moderately active (work out 3-4 times per week)Your activity factor is 1.55Your TDEE = 1.55 X 1339 = 2075 calories/day Determine the energy cost: ______________________

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