Nutritional Considerations for Intense Training and Sports Competition

1. Nutritional Considerations for Intense Training and Sports Competition Chapter 8

2. Effect of Diet on Muscle Glycogen and Time to Exhaustion (1967) Fig 23.1

3. Preparation for Competition • “Competition eating” • Eating strategies • Before, during and after competition • “preparation” • Weeks, months prior

4. Preparation for Competition • Factors to consider • Duration and intensity of exercise involved • Environmental conditions • Temperature, humidity • Training status • *Previously successful strategies*

5. Preparation for Competition • Factors associated with fatigue • Deletion of glycogen stores • Hypoglycemia (low blood sugar) • Dehydration • Hyponatremia (low total body sodium) • GI discomfort

6. Pre-Competition Meal - Protein • CHO: To “top off” liver and muscle glycogen • CHO: digested and absorbed faster • Protein – thermogenesis raises body heat • Protein – breakdown requires water • Fat: Slows digestion • Thus, the ideal pre-event meal should be high in carbohydrates and low in fats and proteins

7. Supercompensation of Glycogen Stores or Carbohydrate loading Classical method • Prolonged strenuous exercise to deplete glycogen stores • A low CHO diet for three days while continuing to train • 90% CHO diet for three days with light or no activity

8. Supercompensation of Glycogen Stores Modified plan • Tapering workouts over several days from 90 to 40 minutes while eating 50% CHO diet • Two days of 20 minute workouts while eating 70% CHO diet • Day of rest eating 70% CHO diet before event

9. Classical and Modified Methods of Glycogen Super-compensation Fig 23.2

10. Pre-Event Fueling • CHO loading • Hawley et al. 1997 • > 90 min duration • Extend duration ~ 20% • Improve performance 2-3% • 45-90 min duration • Little benefit

11. Pre-Event Fueling • Non-endurance events • Glycogen stores normalize by 24 h rest • Adequate CHO intake (7-10 g/kg BM/day) • For events 60-90 min • CHO loading doesn’t improve performance

12. Pre-Event Meal • Readily digestible foods • Should contribute to energy and fluid requirements • Meals high in carbohydrates and relatively low in lipids and proteins • Three to four hours to digest and absorb the pre-competition meal

13. Ideal Precompetition Meal • Contains 150 to 300 grams of carbohydrates • Is consumed 2to 4 hours before the event • Contains little fat • Contains little fiber

14. Liquid Meals • High carbohydrate content • Supply fluids • Digest rapidly • Can be used for day-long events • Typically well tolerated in body weight supported activities (e.g. cycling)

15. Carbohydrates before Exercise • CHO should be eaten >1 hr prior to activity or just prior • Eating CHO in the last hour before competition • Insulin response • Rebound hypoglycemia • Fructose absorbs more slowly than glucose or sucrose. • Can produce significant GI distress • Avoid it

16. Carbohydrates before Exercise • Preventing hypoglycemia • Pre-event CHO • Consume 60g/hr during the event • 1 liter of fluid • 250 ml of 5-8% sugar solution every 15 min for a 70kg man