Transcript Michael Puglisi, PhD, RD

Sports Nutrition
Michael Puglisi, PhD, RD
Estimation of Energy Needs
Energy Source with Aerobic Training
 ~50-60% of energy during continuous exercise at 70%
maximal oxygen capacity is derived from carbohydrates
 Remainder mainly from fatty acid oxidation
 Greater proportion from fat as intensity ↓
 Energy derived from fat ↑ with aerobic training
 ↑ muscle TG utilized for energy
 Prevents glycogen depletion
Coyle E et al. Am J Physiol. 1997.
Low Energy Intake
 ↓ Muscle Mass
 ↓ Bone density
 Menstrual Dysfunction
 Fatigue, Injury, Illness
 Inability to recover between workouts and from injury
 If weight loss is the goal, should take place in the off-season,
not during the competitive season
Weight Loss in Competitive Season
 Loss of lean mass→↓ strength and endurance
 Impaired immune, endocrine and musculoskeletal function
 ↓ Resting Metabolic Rate
 Poor Micronutrient Intake
 Iron deficiency a major concern, especially with female athletes
 ↓ oxygen carrying capacity, critical for endurance athletes
Burke LM et al. J Sports Sci. 2006.
Iron Deficiency
 Plasma volume expansion occurs with training
 ~300 mL for recreational runners
 Up to 1L for endurance athletes
 ↑ Hemolysis with exercise
 “foot strike” hemolysis for runners
 GI Bleeding
 Up to 1/4 of marathoners
 ↓ visceral blood flow, promoting ischemic damage
 ↓ LES pressure
 Needs estimated to be 70% greater
Zoller and Vogel. Nutrition. 2004.
Carbohydrate Intake
 Muscle glycogen stores of a trained athlete are adequate to
fuel exercise up to 60-90 minutes
 Fatigue or ↓ work capacity with prolonged continuous
exercise or high intensity intermittent exercise of 60 minutes
or greater
 Depletion of glycogen stores
Carbohydrate for Weight Training
 Muscle glycogen most likely not depleted
 Possible with sessions of high intensity lasting longer than an
hour
 May be an issue for athletes doing cardio and weight lifting
 Muscle protein synthesis is maximized with addition of
carbohydrate
Carbohydrate Loading
 Previous Protocol
 3 days of low carbohydrate diet + training
 Deplete stores
 3 days of high carbohydrate diet + tapered training or rest
 Current Protocol
 Found that 24-36 hours of rest and a high carbohydrate diet is
sufficient to increase muscle glycogen stores
High Carbohydrate Diet
 8-12 g/kg/day
 For a 70 kg person, 2240-3360 kcal of carbohydate per day
 60-70% of kcal as CHO for 5000 kcal diet
 Okay for an elite athlete
 Pretty difficult for casual athlete or someone who restricts
intake
 Aim for lower end of range
 Not a good idea to overeat just to maximize glycogen
Overall Carbohydrate Recommendations
 Casual Athlete: 50-55% of kcals
• 60-70% for 1-2 days before competition
 Endurance Athlete
 60-65% of intake
 Protein will most likely be adequate given high caloric intake
 ~20% fat
 High fat diet will displace necessary carbohydrate
Carbohydrates during exercise
 Improves performance for exercise lasting longer than 90
minutes
 Intake greater than 1.5g/min lead to oxidation of exogenous
glucose above 1.0g/min
 Alternative fuel source to muscle glycogen, preventing
depletion
 Recommendation is 0.7g/kg body weight per hour
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Shown to improve performance
70 kg person: 49g/hr
8 oz Gatorade has 14 g carbohydrate
~28 oz (3.5 cups) an hour
Jentjens RL et al. Metabolism. 2005.
Timing of Carbohydrate Ingestion
TABLE 2 . Total work and physiological responses during, and plasma lactate at
the end of, 15-min performance ride following 2 h of exercise at 70+/- 1%
[spacing dot above]VO2 peak with ingestion of a sweet placebo throughout
exercise (CON), 7% carbohydrate throughout exercise (CHO-7), or a sweet
placebo for the first 90 min followed by 21% carbohydrate (CHO-0/21).
McConnell G et al. MSSE. 1996.
2
Recommendations During Exercise
 Consume carbohydrates spaced out every 15-20 minutes
 6-8% carbohydrate, primarily glucose
• More concentrated source or fructose may slow gastric emptying
or cause GI distress
 ~3-4 cups/hr
Postexercise Carbohydrates
 Delaying carbohydrate intake for 2 hours after exercise
reduces maximal glycogen repletion 24 hours postexercise
 Recommendations: 1.0-1.5g/kg carbohydrate every 2 hours
for up to 6 hours postexercise
 70 g person: 70-105 g every 2 hours
 Simple if time meal after exercise
 Not critical if resting next day and diet provides adequate
carbohydrate
Ivy JL et al. J Appl Physiol. 1988.
Postexercise Carbohydrates
 Sample 50 gram carbohydrate choices for the foundation of a meal
or snack:
-Wheaties, 2 cups
-Nature Valley Granola Bar, 2 packets (4 bars)
-Thomas’ Bagel, 1 (3.5 oz)
-Banana, 2 medium
-Orange juice, 16 ounces
-Apple, 2 medium
-Raisins, 1/2 cup
-Pepperidge Farm multi-grain bread, 2.5 slices
-Baked potato, 1 large (6.5 ounces)
-Pasta, 1 cup cooked
-Rice, 1 cup cooked
-Fig Newtons, 5
-Flavored Yogurt + 3 graham cracker squares
Carbohydrate Quality?
 Low GI recovery diet
seemed to increase fat
utilization during 90
minute cycling bout at
70% VO2 max
 No sparing of glycogen
 Needs more research
Stevenson EJ et al. Am J Physiol Endocrinol Metab. 2009.
Hydration
 Loss of 2% of body weight impairs performance
 Within 4 hours of exercise: 5-7 ml/kg
• 70 kg: ~12-16 ounces
 During exercise
 Sweat rates vary depend on person, weather conditions, and
intensity of exercise
 0.3-2.4 L/h
 Fluid intake should be adjusted accordingly
Fluid Recommendations
 Adjust based on conditions
 Plan Ahead!
 Longer than 60-90 minutes: sodium aids in fluid retention
(sports drinks)
 Fluid balance is hard during exercise
 Sweat rates may be greater than gastric emptying
 8% carbohydrate or less
 Postexercise: 16-24 oz for every pound of weight lost
 With food: sodium sources
Tips for Performance
 Test out diets around training
 Get used to drinking fluids with longer sessions
 Meal timing and types of foods before competition should be
tested in training
 Plan!
 Not bringing enough food
 Delaying consumption prior to next workout
Protein Needs
 Generally met in the typical Western diet
• Exceptions may be vegetarians or athletes who severely restrict
their intake
 Current RDA (0.8 g/kg) is most likely adequate for most
noncompetitive athletes
Protein and Endurance Athletes
 Nitrogen balance studies estimate needs at 1.2-1.4 g/kg per
day
• ↑ oxidation for fuel with exercise
 Main concern is adequate energy intake to ensure protein
sparing
 Will ensure that other fuels are oxidized, sparing amino acids
for protein synthesis
Phillips SM et al. Int J Sports Nutr Exer Metab. 2007.
Tipton KD and Witard OC. Clin Sports Med. 2007.
Protein and Resistance Exercise
 Extra protein and energy required for muscle growth
 Range from 1.2-1.7g/kg per day
 Once again, usually being met, especially in resistance training
population
 Needs are highest with initiation of training, where most size
gain occurs
 Trained individuals more efficient in protein use
Phillips SM et al. Int J Sports Nutr Exer Metab. 2007.
Protein Quality
 Cuthbertson et al. and Phillips et al.
 ~8.5-10g of EAAs maximally stimulates protein synthesis
 Comes out to ~20-25 g of protein sources of high biological
value
 ~40% EAAs
 ~20-25 oz milk, 3 ounces meat, fish or poultry, ~4 eggs
Cuthbertson DK et al. FASEB J. 2005.
Phillips SM et al. Int J Sports Nutr Exer Metab. 2007.
Protein Synthesis in Response to
Exercise
Phillips SM. Nutrition. 2004.
Muscle protein synthesis and
breakdown
Phillips SM. Nutrition. 2004.
Protein Intake for Strength Athletes
~1.33 g/kg per day
for Nitrogen Balance
Phillips SM. Nutrition. 2004.
Nitrogen Balance
 Adequate to assess prevention of deficiency, but not for
maximizing gains with resistance exercise
 Positive balance necessary for extra amino acids for muscle
growth
 Problems with measurement
 Higher than possible balances with excessive protein intake
 Calculation of loss is hard to estimate
Recommendations Based on Research
for Strength Athletes
 Protein intake for strength athletes will most likely be
appropriate when energy needs are met
 Adequate energy intake is most often the limiting factor and
area that demands more attention for muscle strength gain
Amount of protein in foods
Protein Consumption Around a Workout
 Essential amino acids (EAA) stimulate muscle protein
synthesis
 6 g EAA shown to be just as effective as 40 g for muscle
protein synthesis stimulation postexercise
 No effect from nonessential amino acids
Fig. 6. Muscle protein synthesis as determined by the 3-compartment model
Rasmussen, B. B. et al. J Appl Physiol 88: 386-392 2000
Copyright ©2000 American Physiological Society
Biochemical Society Transactions
www.biochemsoctrans.org
Biochem. Soc. Trans. (2007) 35, 1302-1305
Amino Acid Infusion
 Acutely stimulates muscle protein synthesis
 Starts to fall back to baseline ~2 hours after infusion
 Substrate needs for synthesis met
 Enzymes for amino acid oxidation are upregulated in
response to greater circulating concentrations
Bohe J et al. J Physiol. 2001.
Importance of carbohydrate
 Insulin suppresses protein breakdown
 After resistance training, carbohydrate alone can reduce
muscle protein breakdown
• No effect on muscle protein synthesis
 Combination of protein and carbohydrate around exercise
would be most beneficial
 Milk?
 Amino acids for synthesis, carbohydrate to stimulate insulin,
thus inhibiting breakdown
Borsheim E. et al. J Appl. Physiol. 2004.
Lecker SH et al. J Nutr. 1999.
Ubiquitin Pathway
 Major pathway for protein breakdown
 Insulin reduces Ubiquitin mRNA
 ATP dependent process
 ↑ by fasting
High Protein Intake
 Not shown to detrimentally affect kidney function
 Difficult to link high protein intake with negative health
outcomes

Of course it exacerbates existing kidney disease
 Does it affect performance?
 Yes if you are an endurance athlete or engage in repeated high
intensity exercise
 ~8 g/kg Carbohydrate is considered optimal; tough to reach if
overeating protein
Phillips et al. Int J Sports Nutr Exerc Metab. 2007.
Questions?