Physical activity is a way of life for many PHS Commissioned Corps officers. With the spring approaching, many athletes are currently training for races and gearing up for spring and summer competitions. Proper nutrition is very important for athletic performance and recovery.

Who should be concerned about sports nutrition?
Athletes that exercise vigorously most days of the week for extended periods of time (> 60 minutes/day) can benefit from particular attention to their diet during training and competition. Athletes who train for at least 90 minutes most days of the week can benefit from increased carbohydrate consumption during recovery to replenish glycogen stores.

Energy metabolism during exercise
Energy is the ability to do work. Depending on the type and duration of physical activity, anaerobic and/or aerobic pathways for energy metabolism may be used. Energy is available in various forms (glycogen, adenosine triphosphate (ATP), creatine phosphate, fatty acids, etc.) in the muscle tissue, liver, fat (adipose) tissue, and blood. The primary fuel source during vigorous physical activity is derived from carbohydrate. Therefore, adequate carbohydrate stores are critical for optimum athletic performance.

General Recommendations

• Make sure to consume enough calories as inadequate calorie intake can result in loss of muscle mass, fatigue, a prolonged recovery process and other issues. You can find out what your current energy needs are at the following website: www.supertracker.usda.gov
   
• Carbohydrate recommendations range from 6 to 10 grams(g)/kilogram (kg) (2.7 to 4.5 grams/pound) body weight per day in most athletes. In general, the following amounts of carbohydrate are typically needed:
  1. 6 to 7 g/kg/day for training (>1 hour per day)
  2. 7 to 10 g/kg/day for endurance (1-3 hours per day)
  3. 10 to 12 g/kg/day for ultra endurance (3-5 hours per day)
  4. 3 to 5 g/kg/day for moderate activity
  5. 2 to 3 g/kg/day for weight loss may be appropriate depending on activity
  
  
• Protein recommendations for endurance and strength-trained athletes range from 1.2 to 1.7g/kg (0.5 to 0.8 g/lb) body weight per day. These recommendations can be met through diet alone and without the use of additional protein or amino acid supplements
   
• Fat recommendations are between 20 to 30% of total energy (calorie) intake.
   
• Hydrate, hydrate, hydrate. Adequate fluid intake before, during and after exercise is important for preventing dehydration. Consuming sports drinks with electrolytes and carbohydrate will help to replace losses of those nutrients and aid in recovery. Here are some general guidelines for fluid intake:
  1. 16 to 20 ounces 2 hours before training/competition
  2. 6-8 ounces every 15-20 minutes during exercise
  3. Use a sports drink with carbohydrate and electrolytes if you are exercising for more than 60 minutes at high intensity
  4. Athletes should aim to replace sweat losses during exercise by consuming 16 to 24 ounces fluid for every pound of body weight lost during exercise.
  
  
• Before a race or competition eat a meal or snack that provides carbohydrate and fluids. Foods that are low in fat and fiber (e.g., bagel, pretzels, etc.) may prevent stomach upset during intense physical activity.
   
• During exercise aim to replace fluid losses and consume carbohydrates for maintenance of blood sugar levels. Approximately 30 to 60 grams of carbohydrate per hour is typically needed.
   
• Don’t wait to hydrate or consume carbohydrate. By the time you feel dehydrated or sluggish it is too late! Try using a sports drink and/or other product specially formulated for replacing carbohydrate and electrolytes within the first 30 minutes of your physical activity.
   
• After exercise carbohydrates are needed to replace muscle glycogen stores. Recommendations are to consume about 1 to 1.5 g/kg (0.5 to 0.7 g/lb) body weight during the first 30 minutes and then again every 2 hours for 4 to 6 hours after intense training or competition. Sports drinks, fruit, salty snacks such as pretzels or crackers, and low-fat candy (e.g. gummy bears) can help to replace carbohydrates and/or electrolytes.
   
• Use performance-enhancing supplements (e.g. creatine, caffeine pills, etc.) with caution. These products are not regulated in the U.S. and should only be used after a careful evaluation for safety, efficacy, potency, and legality. It is recommended that you consult with your doctor or other medical care provider before taking performance-enhancing supplements.
   

References

Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Am Diet Assoc. 2009;109:509-527.