My sports nutrition Q&A coincides perfectly with my weekend plans. Saturday I am partaking in a 80 mile relay with 6 friends. We will all run about the equivalent of a half marathon and make our way from Naples beach to Sanibel and back! I gathered a handful of questions from facebook and wordpress so let’s get to it!
Dehydration – does it affect performance?
We sweat to reduce the heat load and reduce our core temperature. There are many fluid shifts that also occur during exercise as heart rate increases which results in fluid leaking from the blood vessels into the surrounding space (called the interstitial space). With greater sweat loses, more fluid is lost from the plasma (the blood vessels) and this can have detrimental effects.
While athletes are encouraged to take fluids during endurance exercise, gastric emptying, or the rate of absorption may be a limiting factor. While there is a chance of overhydration and drinking too much, typically only 1.0 – 1.5 liters of fluid can be comfortably absorbed per hour. Each athlete also has a unique sweat rate that may fluctuate based on conditions like temperature, humidity, clothing, and intensity. Remember, consuming too much fluid is also harmful and can lead to hyponatremia. Check out these tips for endurance events and avoiding hyponatremia from the Boston Marathon: http://www.baa.org/races/boston-marathon/participant-information/hydration-information.aspx
Research has show that a loss of 3-5% of body weight does NOT reduce anaerobic performance or muscular strength, but it does affect thermoregulation which increases the risk of heat illnesses such as heat stroke. Therefore a hydration plan is important for safety. It is not expected that all fluid loses be replaced during exercise, and it is likely not feasible. Water, or H2O is also an important component in anaerobic (oxygen requiring) energy production so you can see the importance for endurance events (affects perceived exertion and pace). Sweat loses up to 10% of body weight are not uncommon for endurance events (if fluids are not replaced), which can have detrimental effects. For athletes training and preparing for endurance events it is best to calculate your personal sweat rate and plan a hydration routine to match. Check out this hydration tool from Runner’s World: http://www.runnersworld.com/tools/hydration-calculator
Pre workout foods – What should I eat prior to a work out?
These foods need to be easily digestible and typically low in fiber, to minimize gastric distress. Studies have shown that carbohydrate intake 3 to 4 hours prior to endurance exercise is beneficial in a ratio of 3 grams of carbohydrate per kg of body weight. To find out how many kg you weight, divide your weight in pounds by 2.2 (150lbs/2.2=68kg). Then take your weight in kg and multiply by 3 grams of carbohydrate (68kg x 3 g = 204 g of carbohydrate). Including some protein and fat in this meal is also beneficial for preventing feelings of hunger during exercises. If you only have 1 hour prior to exercise consume 1 gram carbohydrate per kg, if you have 2 hours prior to exercise consume 2 gram carbohydrate per kg.
Typically foods and meals eaten prior to exercise need to be tested and trialed during training, listening to your body for tolerance and impacts on performance.
Post workout foods – What should I eat after exercise?
Studies have shown consuming 20 grams of protein after weight training exercise leads to an increase in lean muscle mass. Elite endurance athletes who have a heavy training load also need to be concerned about replacing carbohydrate stores, or glycogen, and should have a carbohydrate containing meals within one hour of exercise.
The average athlete, take me for example, does not need to be as concerned about the macronutrient composition of meals after exercise. My typical routine includes running 25 miles a week, resistance training two times per week, and a yoga or spinning class. I do not need to be as concerned with replacing my glycogen stores because I have plenty of rest between training sessions and they will be adequately replaced through regular meals. Even though I am training for a half marathon, my carbohydrate needs can be met through regular meals and snacks. That is not to say that I do not contain a carbohydrate containing meal after my long runs, but remember many nutrition recommendations that are mainstream are actually directed towards elite athletes that are training 3+ hours per day, 7 days a week!
Bottom line, maintain a healthy diet for optimal sports nutrition!
Protein shakes – What’s the deal?
Like I mentioned a 20 gram protein shake after exercise may help increase lean body mass. However, to get the desired results of increasing lean body mass, the training program is just as important! Resistance training increase protein needs, for building and repairing skeletal muscles (along with maintaining a healthy immune system and replace daily protein loses). Protein supplements will help reach these increased protein needs, but are no more or less effective than food sources of protein.
Endurance athletes also have increased protein needs, so protein supplements may be a convenient way of reaching this target and may be incorporated into their sports nutrition plan. Protein shakes are receiving more attention for weight loss and satiety and can be a part of any healthy diet. Breakfast meals are usually inadequate in protein and may be a great opportunity to get in a source of lean protein.
The bottom line…
Evaluate what level of an athlete are you? Are you pulling two-a-days or just a weekend warrior?
Listen to your body! We all tolerate foods differently especially when it comes to timing of before, during or after.
Get professional help! Have questions, or think your diet is holding you back? Seek out an expert in the field. Sports nutrition is very unique to the individual, the event, and therefore the nutritional needs. Find a local dietitian here: http://www.eatright.org/programs/rdfinder/
Dunford M, Doyle JA. Nutrition for Sport and Exercise. 2nd ed. Belmont, CA: Wadsworth; 2012.