NUTR250 Human Nutrition and Metabolism Chapter 11 PDF

NUTR250 Human Nutrition and Metabolism Chapter 11 Nutrition, Exercise, and Sports Dr. Keting Li, FDST, UNL Benefits of Regular and Moderate Exercise Physical Activity Guidelines – 3 Goals 1. Adults should move more and sit less throughout the day and some physical activity is better than none 2. For...

NUTR250 Human Nutrition and Metabolism Chapter 11 Nutrition, Exercise, and Sports Dr. Keting Li, FDST, UNL Benefits of Regular and Moderate Exercise Physical Activity Guidelines – 3 Goals 1. Adults should move more and sit less throughout the day and some physical activity is better than none 2. For health benefits, each week adults should engage 150 min/week of moderate intensity aerobic exercise OR 75 minutes/week of vigorous intensity exercise 3. Should perform muscle-strengthening activities on 2 or more day per week. lifting weights working with resistance bands heavy gardening, such as digging and shoveling climbing stairs hill walking cycling dance push-ups, sit-ups and squats yoga Characteristics of a Good Fitness Program A good fitness program meets a person’s needs. To reach goals, fitness program planning should consider: Mode Frequency Intensity Progression of exercise Consistency Variety Achieve and maintain fitness Characteristics of a Good Fitness ProgramExercise Modes Aerobic exercise: Any activity that uses large muscle groups, can be maintained continuously, and is rhythmic in nature. Causes the heart and lungs to work harder than at rest Brisk walking, running, swimming, cycling Characteristics of a Good Fitness ProgramExercise Mode Resistance exercise (or Strength training): Activities that use muscular strength to move a weight or work against a resistant load Flexibility exercise: Increases the ability of a joint to move through its entire range of motion Characteristics of a Good Fitness Program-Duration Duration The amount of time spend in an exercise Last at least 30 minutes, not counting time for warm-up and cooldown. Ideally, exercise should be continuous. How to avoid quitting workouts Start slowly, small steps Vary activities; make exercise fun Include friends and others Reward yourself for being successfully in keeping up with your goals Focus on long-term benefits to your health Characteristics of a Good Fitness Program-Frequency Frequency The number of times an activity is performed weekly Best fitness level: daily Cardiovascular fitness: 3-5 days/week Weight loss: 5-6 days/week Muscular fitness: 2-3 days/week resistance training Characteristics of a Good Fitness Program- Intensity The level of effort required, or how hard the exercise is to perform Low intensity: Very mild increased heart rate Moderate intensity: Increased breathing, sweating, and heart rate Can still hold a conversation High intensity: Significantly increased breathing, sweating, and heart rate Difficult to carry on a conversation Characteristics of a Good Fitness Program- Intensity Heart rate Use a percentage of age-predicted maximum heart rate Maximum heart rate (MHR) = 220 – Age in years Heart range between 60 and 90% of maximum is called target zone. e.g., the target zone for a 20-year-old person is 120 to 180 heartbeats per minute Characteristics of a Good Fitness Program- Intensity Borg Scale of Perceived Exertion (Rating of Perceive Exertion scale, RPE) Ranges from 6 to 20, with numbers corresponding to subjective feeling of exertion To achieve fitness, aim for 12-15 Characteristics of a Good Fitness Program- Intensity Measure oxygen consumption In this test, O2 consumption is measured as the treadmill speed and/or grade is gradually increased until the subject can no longer increase O2 consumption as workload increases. VO2max – Maximum volume of oxygen that can be consumed per unit of time during exercise Individual differences in VO2max Intensity is best described in % of VO2max Characteristics of a Good Fitness Program- Intensity Metabolic Equivalents (METs) One MET is the amount of energy used while sitting quietly Approximates Resting Energy Expenditure E.g., energy needed to walk 4.0 mph on a flat surface is 5 METs Characteristics of a Good Fitness ProgramProgression How the duration, frequency and intensity of exercise increase over time Initiation phase (first 3-6m): body adapts to the exercise program Improvement stage (next 5-6m): intensity and duration increase to a point that no further physical gains are achieved; beginning of maintenance stage-may need to adjust their exercise Characteristics of a Good Fitness ProgramConsistency To make it part of a daily routine Best time is whenever it fits one’s lifestyle; however, working out before bedtime has usually been discouraged Characteristics of a Good Fitness Program-Variety A varied fitness routine helps exercise different muscles for overall fitness Keep exercising interesting and fun! Energy Sources for Muscle ATP A resting muscle cell contains a small amount of ATP Just enough to keep the muscle working maximally for about 1-2 seconds. Phosphocreatine (PCr) PCr is activated instantly PCr is used to replenish ATP from ADP quickly PCr stores last for ~10 sec Dietary carbohydrates, fats, proteins Release more energy to make more ATPs Spare some PCr use Energy Sources for Muscle Carbohydrates: Major fuel for short-term, high intensity, and medium-term exercise Anaerobic Pathway Limited O2 supply and/or very high-intensity activity (running 200 meters, swimming 100 meters) Carbohydrate ONLY fuel Advantages: fastest way to resupply ATP in muscle (other than PCr breakdown) Disadvantages: can’t sustain ATP production for long (maximal energy production for 30-120 sec) Accumulation of lactate and H+ causes fatigue Lactate released into the bloodstream – heart use for energy; liver takes up some of lactate and resynthesize it into glucose Carbohydrates: Major fuel for short-term, high intensity, and medium-term exercise Aerobic Pathway Plenty of O2 available and moderate- to low-intensity activity (e.g., jogging, distance swimming) Slower than anaerobic pathway but more efficient than anaerobic Activities lasting from 2 min to 3 hours Energy systems used to fuel exercise change with duration of exercise. Glycogen Storage Glycogen is the temporary storage form of glucose in the liver (~100 g) and muscles (~400 g in sedentary people). Liver glycogen is used to maintain blood glucose levels Muscle glycogen supplies the glucose to the working muscle < 2 h during fairly intense activities Exercise < 30 mins, muscles rely on muscle glycogen as fuel >30mins, muscle glycogens decline, and muscles take up blood glucose for fuel Glycogen Depletion The depletion of muscle glycogen → fatigue The depletion of liver glycogen → fall in blood glucose “Hitting the wall”: Glycogen stores are exhausted or depleted. A person can continue working at 50% maximum capacity. Fat: Major fuel for prolonged, low intensity (aerobic) exercise During prolonged exercise at low intensity, fat is the predominant fuel source. Fat supplies about 50 to 90% of energy required during very lengthy activities (e.g., triathlon) The rate at which muscle use fatty acids is affected by training level. The more trained a muscle, the greater its ability to use fat as a fuel. Training increases: Triathlon Size and number of mitochondria Enzymes for aerobic pathway Fat: Major fuel for prolonged, low intensity (aerobic) exercise Advantages High energy (9 kcal/g) High ATP yield Large storage of fat in body compared to limited glycogen storage Disadvantages Cannot occur fast enough for shortduration, high-intensity activities Do NOT support anaerobic activity ATP Yield from aerobic fatty acid metabolism and aerobic glucose metabolism. Protein: A minor fuel source during exercise Make a small contribution Most of the energy from protein comes from breakdown of branched-chain amino acids (BCAAs): Enter gluconeogenesis or citric acid cycle Fluid Needs for Active Individuals Fluid is needed to: Maintain blood volume Regulate body temperatures Prevent heat exhaustion, heat cramps, heatstroke Dehydration (>2% of weight loss from sweating): Endurance ↓↓ Strength ↓ Cognitive performance ↓ Effects of Hypohydration 1. Heat exhaustion Symptoms: Headache, dizziness, nausea, vomiting, muscle weakness Take to cool environment, remove excess clothing 2. Heat cramps Complication of heat exhaustion Prevention: avoid dehydration, adequate salt 3. Heatstroke (core temp > 104F) Symptoms: Hot and dry skin, nausea, confusion, irritability, seizures, rapid heart rate, diarrhea, coma Death can occur if untreated Treatment: Cool skin (ice, water) until medical help arrives Dehydration is the process of losing water, while “hypohydration” is the actual state of being in a water deficit beyond what is normal Fluid Intake and Replacement Strategies Before exercise: Drink about 2-3 cups fluid about 2-3 hours before exercise During exercise: 1-1.5 cups every 10 to 15 minutes Prolonged exercise: beverage containing 4-8% carbohydrates; 0.50.7 g/L of sodium After exercise Hydrate adequately after exercise Monitor urine color (No darker than lemonade) Water Intoxication Over drinking without replacing sodium losses Hyponatremia: deficiency of sodium in the blood Prevention: Drinking beverages that contain sodium. Sports drinks with 100 mg of sodium per 8 ounces Sports Drinks Carbohydrates: Glucose to support depleted glycogen Enhance performance Electrolytes: Maintain blood volume Enhance absorption of water and carbohydrates