Chapter 13

Lecture 1: Physical Activity Definition

  • Physical activity: any muscle movement that increases energy expenditure
    • Includes purposeful/planned exercise
    • Also includes leisure, work, or unconscious movement: walking, taking the stairs, standing
  • Physical fitness: state of being created by the interaction of nutrition and physical activity
    • Cardiorespiratory fitness
    • Musculoskeletal fitness
    • Flexibility
    • Body composition
  • Canadian 24-Hour Movement Guidelines:
    • Physical Activity:
      • Moderate to vigorous aerobic physical activities, accumulating at least 150 minutes per week
      • Muscle strengthening activities using major muscle groups at least twice a week
    • Sleep:
      • 7-9 hours of good-quality sleep on a regular basis, with consistent bed and wake-up times
    • Sedentary Behaviour:
      • Limiting sedentary time to 8 hours or less
      • No more than 3 hours of recreational screen time
      • Breaking up long periods of sitting as often as possible
      • Several hours of light physical activities, including standing
  • Physical activity in Canada:
    • Varies geographically; refer to the map for specific percentages in different regions.
  • Physical activity & health:
    • Proportion (%) of disease cases attributable to physical inactivity:
      • Osteoporosis
      • Stroke
      • Type 2 diabetes
      • Heart disease
      • Colon cancer
      • Breast cancer
      • Hypertension
  • Reaping the benefits of physical activity:
    • More than ½ of all Canadian adults do not do enough physical activity
    • In Edmonton, only 50% of people are active enough to reap the benefits of activity
    • Inactivity is more prevalent in women than men, and in girls vs boys

Lecture 2: Fuels Usage During Exercise

  • Eating for exercise is an issue of:
    • Fuel
    • Hydration
    • Nutrients of concern
  • Types of fuel, source and availability:
    • ATP: 1-3 seconds
    • Creatine phosphate: 3-15 seconds
    • Glucose: 15s onward
    • Fatty acids: 2min onward
  • Fuel for physical activity
    • Adenosine triphosphate (ATP) – the energy carrying molecule in the body
    • ATP must be generated continuously since muscles have only enough ATP for 1-3 seconds of activity
  • Creatine phosphate
    • After depleting ATP stores, muscles turn to other sources:
      • Creatine phosphate stores some energy that can be used to make ATP
      • Creatine phosphate stores enough energy for 3-15 seconds of maximal physical effort
  • Fuel for physical activity
    • After creatine phosphate, carbohydrates are the next source of energy for the production of ATP
    • Glucose is the primary carbohydrate used to generate ATP
  • Fuel for PA - Metabolism of glucose
    • Glucose (C6H{12}O_6)
    • Glycolysis occurs in the cytoplasm, producing pyruvic acid and 2 ATP (Anaerobic respiration)
    • In Aerobic respiration, the citric acid cycle and electron-transport chain produce 6CO2 + 6H2O + 38ATP
  • Fueling Exercise by the Minute
    • ATP and creatine phosphate provide instant energy (10 sec)
    • Glucose provides short-term energy (anaerobic metabolism) (30 sec - 2 min)
    • Fatty acids and glucose provide long-term energy (aerobic metabolism) (10 min onward)
  • Fuel for physical activity
    • Triglycerides (fats) can be metabolized to generate ATP
      • For low intensity exercise
      • For exercise of long duration
      • A very abundant energy source, even in lean people
    • 9 kcals/g compared to 4 kcals/g – LOTS of energy!
  • Burning stored glycogen vs fat depends on…
    • Activity intensity: higher intensity = more carbohydrate used (per minute)
    • Activity duration: longer duration = more fat used in total (glycogen storages depleted)
    • Individual training level: untrained muscles deplete glycogen more rapidly
    • Individual diet composition: high CHO diets increase the amount of stored glycogen
  • The Effect of Exercise Intensity
    • At rest the body uses mostly fatty acids for energy.
    • During moderate-intensity activity, the body uses a mix of fatty acids and glucose.
    • During high-intensity activity, the body primarily uses glucose for energy.
  • Fuel for physical activity
    • Carbohydrates and fats can both be used as energy sources for the production of ATP
      • Carbohydrates are mostly used to fuel high intensity movement
      • Fats are used to fuel low intensity (but longer duration) movement
    • Under normal conditions, proteins (amino acids) are not used as a fuel source for exercise

Lecture 3: Hydration

  • Fluids and hydration
    • Maintaining water balance is critical for physically active people
    • Dehydration: lack of body water
    • Water is essential for:
      • Digestion and absorption of nutrients
      • Waste product excretion
      • Maintenance of blood volume
      • Temperature regulation
  • Hydration & physical activity
    • Avg fluid losses (70 kg man): sedentary
      • Insensible losses: 700 ml
      • Urine: 1400 ml
      • Feces: 100 ml
      • Sweat: 100 ml
      • Total: 2300 ml
    • Avg fluid losses (70 kg man): 2h training at 30C
      • Insensible losses: 1000 ml
      • Urine: 500 ml
      • Feces: 100 ml
      • Sweat: 5000 ml
      • Total: 6600 ml
    • Cannot cure dehydration during sport – need to prevent and pre-hydrate
  • Fluid requirements for athletes
    • Environmental conditions
      • Heat, humidity or both (Humidex)
      • Clothing
    • Metabolic needs
      • Growth, pregnancy or breastfeeding
    • Activity level
      • Duration, intensity, type
  • ACSM Fluid Guidelines
    • 2 hours before exercise: 400-600 ml
    • During exercise: 180-360 ml every 15-20 min
    • After exercise: at least 450-675 ml per 1 lb of weight (water) lost during exercise
  • Recommended fluid sources
    • For exercise lasting < 1 hour
      • Plain, cool water
    • For intense exercise lasting > 1 hour
      • Plain, cool water
      • CHO/fluid replacement beverages
        • Help to replace CHO and fluid
        • May enhance endurance
        • Sport drinks (ie Gatorade)
        • ?Tolerance – trial during training
  • Monitoring hydration
    • Urine colour
      • Pale and plentiful
    • Body weight
      • Weigh in before and after exercise
      • 1 lb = about 500 ml fluid
    • Signs/symptoms of dehydration
      • Thirst, headache, fatigue, irritability, nausea, chills, collapse
  • %BW Loss and Effects (80kg)
    • 1. 5-2% BW loss: Body temp control, performance affected
    • 2. 5-3% BW loss: Performance 5-10% Pulse rate, core temp
    • 3. 5-6% BW loss: Strength, coordination, endurance
    • 4. 5-9% BW loss: Heat stroke, heat exhaustion, the person is likely to collapse

Lecture 4: Training Diet

  • Training diet: the eating pattern that a competitive athlete follows to prepare for their event
  • Goals:
    • Maintain body weight
      • Dieting during periods of intense training is not advisable
    • Enhance performance
      • Training, recovery and competition
    • Meet basic nutritional needs and maintain health and wellness
  • Training Diets
    • “A good diet does not make an average athlete great, but….
    • A poor diet can make a great athlete average” - Dr. David Costill
  • Training diets vary depending on the specific sport involved
    • Sprinting vs marathon running
    • Nutrient requirements of the athlete vary by sport
    • Some recommendations are common to the diets of all athletes
  • Nutrition for training: energy
    • Energy (or calorie) needs vary by:
      • Age
      • Genetics
      • Type of sport
      • Training routine and goals
      • Body size and composition
      • Needs may be very high for training athletes, ie 5400 kcal/d for a 90 kg adult body builder in the building phase of training
  • Low energy intakes = poor sport performance
    • Loss of muscle mass (power & endurance)
    • Fatigue
    • Increased risk for injury and illness
    • Menstrual dysfunction, leading to long-term consequences for bone health
  • Nutrition for physical activity - Macronutrients
    • Generally – recommended diet includes
      • 45-65% of kcal from carbohydrates
        • 6-10 g/kg body weight/day
        • CHO is the limiting fuel needed to support vigorous exercise
      • 20-35% kcal from fat (< 30%)
      • 10-35% kcal from protein
        • Endurance: 1.2-1.4 g/kg/day
        • Strength: 1.2-1.7 g/kg/day
        • 12-20% of total kcal
  • Effect of CHO consumption on endurance
    • High-carbohydrate diet increases initial muscle glycogen and time to exhaustion.
    • High-fat diet decreases initial muscle glycogen and time to exhaustion.
  • Low carbohydrate diets
    • Decrease glycogen stores
    • Decrease blood glucose levels
    • Decrease aerobic endurance
    • Promote loss of lean body mass
    • Strength, power, muscular endurance
  • Training Diet: micronutrients
    • The requirements for some vitamins and minerals may be altered in athletes
      • B vitamins
        • Thiamin, riboflavin, niacin: produce ATP from carbs and fat
        • B6, folate, B12: needed for synthesis of RBCs
        • B6: glycogen breakdown
      • Calcium
        • Weight bearing exercise can increase bone density
        • Female athletic triad can decrease bone density: restrictive eating, large amounts of exercise, hormonal changes
  • Training Diet: micronutrients (cont’d)
    • Requirements for iron in athletes may be increased
      • Due to: increased RBC production; an increase in iron loss with training
      • Iron deficiency common in female athletes
        • Impairs exercise, reduces immunity
    • Adequate intake of these nutrients can easily be met with a healthy diet and should not require supplementation
  • Sports Anemia
    • Sports anemia is not a true form of anemia
      • Poor intake
      • Foot strike hemolysis
      • Increase in losses
      • Blood volume (amount of blood in total) expands in response to training
        • Hemoglobin production sometimes lags behind somewhat
    • Treatment of sports anemia is not necessary
      • Given time, the situation will normalize provided dietary iron intake is adequate

Lecture 5: Competition Eating and Ergogenic Aids

  • Competition eating
    • Specific adjustments to timing and food choices the day of event (+/- few days prior)
  • Goals:
    • Improves performance and/or endurance
    • Prevents the sensation of hunger but food digested to the point that it has left the stomach (avoid psychological distraction)
  • Competition eating: GOLDEN RULE
    • Never, EVER try a new food or food combo on the day of a major competition or event!
      • Results could be disastrous!
    • Instead, trial your competition food plan during training
      • Go with what works
  • What to eat pre- competition/practice
    • Week before, use modified CHO loading
      • Only beneficial for longer endurance events
      • Eat 55% of kcals as CHO 4-7 days before event + rest
      • Increase CHO intake 5-10% 0-3 days before event
    • 1 Day out/the night before
      • Avoid consuming excessive fibre
      • Don’t change things drastically
      • Get adequate fluid
    • 4hrs out
      • Balanced meals (eggs and veg on toast, grilled cheese with side of veggies, pasta and meat sauce)
      • Again, keep it like what you would normally eat pre competition
    • 2 hours out
      • Reduce fibre, protein, and fat intake to almost none if possible
    • 1 hr out
      • Keep it to simple carbs (fruit, low fibre cereal, low fibre bread) 30 mins out; low in protein/fibre/fat
    • Simple sugary carbs (sports drinks, low fibre fruit)
  • During/Intra-competition fueling
    • Only really important if:
      • You skipped your pre competition meal
      • You have a long training session/competition >1hr
      • Need to be prepared for a subsequent performance (tournaments, second game the next day)
      • Have trouble putting on/keeping on weight
    • Intra-workout nutrition consists of
      • Mostly sugary carbs: 6-10 g CHO/100ml fluid
      • Done in conjunction with water and electrolytes if the competition is long or hot
  • Sport drinks and supplements
    • Ergogenic aid: a substance that improves exercise performance
    • Sport drinks/aids can contain: CHOs, fluid, electrolytes, other nutritional aids (ie caffeine)
    • Factors to consider when using nutritional sport aids:
      • Palatability
      • Athlete preference
      • Solid food (ie banana) + water
      • What is available
  • Post training/Competition
    • Promote recovery
      • Protein: to help rebuild muscle tissues and keep immunity high
      • Carbs: refill glycogen stores, alleviate stress
    • First nutrient intake should aim for <30 mins after
      • Helps jumpstart recovery
      • Focus on getting easily digestible sources
      • 1-2 hrs post include some fats but keep carbs and protein high (ratio of 4:1 by weight)
      • 4 hrs post return to more normal dietary habits (if no competition next day)
  • Peak Rate of Glycogen Replenishment
    • Glycogen is replenished most effectively in the first 15-30 minutes after exercise.
  • Ergogenic Aids
    • Ergogenic aids: substances used to improve exercise and athletic performance
      • Many of these products are not effective
      • Some of these products are dangerous
      • Reliable research and accurate info on these products is hard to find.
  • Used to increase muscle mass and strength
    • Ie anabolic steroids
      • Serious health consequences
    • Creatine
      • Doesn’t seem to enhance endurance
      • Research is inconclusive about benefits in terms of muscle mass accretion
  • Used to increase feelings of alertness, vitality and/or to optimize fuel use:
    • Caffeine (some side effects)
    • Ephedrine (not approved for sale in Canada)
    • Carnitine (no proven benefit)
    • Chromium (no proven benefit)
  • Summary
    • For optimum sports performance
      • Choose a well-balanced training diet
      • Consume adequate amounts of fluid before, during, and after exercise
      • Enjoy a pre-exercise meal (2-4 hours) and/or snack (30-60 min) before exercise
      • Avoid the use of ergogenic aids