Sports Nutrition

Maximizing your sports performance is dependent on exercise training, genetics, nutrition, hydration and sleep. One major component that is within your control is your nutrition. Remember when your body is hungry, it wants NUTRIENTS, not calories!

PHYSIOLOGY

Food has to be converted to energy, known as ATP, in order for our muscles to use it for running, jumping, pitching, hitting, etc.  ATP is found in all tissues but it is in short supply.  If you require energy for longer periods of physical activity or exercise then it must be harvested from other sources.  There are four main ways to generate ATP – muscle cells, auto-generation, carbohydrates and fat.

Muscle cells have small amounts of ATP but this can only generate energy for very short durations, 1-2 seconds. This is what you use for quick sprints.

Your body can also create ATP by adding other molecules and this energy is available for short bursts. This is what you use for shot put, high jump or bench press.

Eating carbohydrates is another source of energy (ATP). Your body can convert carbohydrates to ATP through two separate pathways:

  1. Provides energy for high intensity exercise lasting 30 seconds – 2 minutes. This is called the anaerobic (without oxygen) pathway and is used for a 200-meter sprint or a 50-meter swim.
    1. A byproduct of the anaerobic pathway is lactate. When this accumulates your muscles get fatigued and you are unable to generate or maintain the same level of exertion and effort.
  2. Provides energy for long distance or endurance activities lasting 20 minutes to 3 hours. This is called the aerobic (with oxygen) pathway and is used for jogging, soccer, basketball and swimming.
    1. In the aerobic pathway, ATP is released slowly and more efficiently
    2. It is critical to maintain blood glucose levels as muscle will “recruit” energy/ATP from this source if carbohydrate conversion is running low.

Fat can also be converted to ATP and this pathway is used during long distance running, marathons and ultra-marathons.

  1. The better your level of muscle training the more efficient your body/muscles are at             converting fat for energy.

NUTRITIONAL GUIDELINES

Food is Fuel and your energy availability (EA) is what determines your performance and if you have enough energy to insure appropriate hormonal and metabolic functions.  Low EA leads to fatigue, poor performance, increased risk of injury and impaired or prolonged recovery.

Carbohydrates are the primary source of energy, therefore optimizing intake of this vital nutrient is paramount.

– If you don’t eat enough carbohydrates muscle glycogen decreases (this is where you                                     store ATP) and performance declines

– If you eat too much carbohydrates it gets stored as fat

Recommended Intake for Carbohydrates  
Low-intensity exercise 3 – 5 g / kg of body weight
Moderate intensity exercise 5 – 7 g / kg of body weight
Endurance exercise for < 4 hours 6 – 10 g / kg of body weight
Endurance exercise for > 4 hours 8 – 12 g / kg of body weight

Protein helps with muscle synthesis and repair.  For this nutrient it is not just quantity but also the quality of the protein.  We need to “eat” our essential amino acids (EAA) because our body does not make them. We also need branched-chain amino acids (BCAA), the most critical of them is Leucine.

Recommended Intake for Proteins  
Endurance athlete 1.2 – 1.4 g / kg
Strength Athlete 1.6 – 1.8 g / kg
Vegetarian Athlete 1.3 – 1.8 g / kg
   
Recommended Intake for Leucine is 2-3 g /day  
12 oz milk 2,000 mg
3 egg whites 990 mg
1 cup of 1% cottage cheese 2,880 mg
3 oz of chicken breast 3,690 mg

NUTRIENT TIMING

Pre-exercise meal should be primarily carbohydrates with moderate amounts of protein and low in fat and fiber.  If you’re eating within 1 hour of your sport then do not consume more than 1 g / kg of carbohydrates.  If you are eating 3-4 hours before exercise then you can consume up to 3 – 4 g / kg of carbohydrates.

During exercise and if the duration is less than 45 minutes then there is no need to consume additional carbohydrates. If however, you are exercising for 1 – 2.5 hours (even if it is a stop-start sport) it is recommended to take in 30 – 60 g /hr. of carbohydrates.

Post-exercise nutrition goals should be to refill muscle glycogen. This synthesis is highest 4 – 6 hours after exercising and it is recommended to consume 1 – 2 g / kg / hr.  To be most effective, combine protein (for muscle synthesis and repair) and carbohydrates (for glycogen / ATP)

Author: Dr. Siatta Dunbar, MHealth Fairview

References

Madden, Christopher C, et al. Netter’s Sports Medicine. 2nd Edition. Elsevier, 2010.