Fuelling Right = Performing Right.
Athletes have many strategies they can use when fueling for performance. Nutrition can play a crucial role in optimizing training sessions as well as with recovery and metabolic adaptation. Athletes should be able to obtain both adequate macronutrients (protein, carbohydrates, fats) and micronutrients through a variety of foods. Sports medicine providers should help athletes navigate the many facets of sports nutrition, including food composition, nutrient timing, supplement use, and energy balance. Additionally, athletes’ nutritional requirements may vary widely depending on sport, position, timing of season, and training vs rest day. Most athletes will plan to either gain lean muscle mass, lose fat, or maintain their current body composition while not impeding their performance on the field. It can be difficult for an athlete to navigate all the various “fad diets” and “healthy” choices when shopping or eating outside the home. Athletes also need to be educated on the detrimental effects of rapid weight loss strategies for competitive advantage, especially in sports such as wrestling and gymnastics. Detrimental effects include hypohydration and loss of glycogen stores and/or lean muscle mass.
The thermic effect of food is roughly 3% to 10% of caloric expenditure but may vary depending on the types of food eaten and is not usually incorporated into energy expenditure calculations. This effect reflects the energy it takes for the body to digest food consumed. This is where some advocates have proposed eating small frequent meals to continue to fuel your metabolism, especially when athletes are looking to lose fat while keeping lean mass.
Another easy way to estimate baseline caloric needs is to multiply weight (lbs) by 14. One caveat is that this calculation should not be used in athletes with more than 30% body fat, as it would overestimate caloric needs. With any of the above equations, it is important to follow caloric intake and training for a couple weeks and then adjust based on an athlete’s progress. Once an estimate for an athlete’s total EI is determined, macronutrient needs can be calculated
The 3 main macronutrients are protein, carbohydrate, and fat. It is important for athletes to consume the optimal ratio of macronutrients in their diet based on their training goals, such as gaining muscle or losing fat while maintaining lean mass. Food quality is also very important, as whole foods should be consumed whenever possible versus packaged foods and bars or shakes. Shakes can be a good source of nutrition but should be made with whole ingredients without added sugars. An example of a whole food shake would be the following: 1 cup unsweetened almond milk, 1 cup frozen banana or berries, 1 tablespoon coconut oil, 1 cup plain Greek yogurt, and 1 to 2 scoops of protein powder. This would contain approximately 400 calories and have around 30 g of protein and 30 to 50 g of carbohydrate.
Protein and carbohydrates have 4 kcal per gram, while fat has 9 kcal per gram when calculating an athlete’s needs. Alcohol is not a macronutrient but does have 7 kcal per gram and is obviously discouraged for optimal training and health.
Proteins are important for many body processes. Not only are they the building blocks of muscle, tendons, and other soft tissues, but they also are essential for building enzymes, hormones, and neurotransmitters for many bodily functions.
Carbohydrates are the main energy source during high-intensity activity for the central nervous system as well as muscular work. Carbohydrates have been vilified in the media lately with their link to the obesity epidemic and possible gut inflammation. This has also led to the explosion of available gluten-free products, but the vast majority of people do not need to avoid gluten as there are many health benefits to eating a diet rich in whole grains. This can lead to a lot of confusion for an athlete trying to make good food choices to fuel his or her body. Carbohydrates are not all created equal, as there is a vast difference between eating a bowl of oatmeal versus a bowl of ice cream. Whole grains, fruits, vegetables, and legumes are highly nutritious foods that are rich in antioxidants, fiber, vitamins, and minerals, while processed sugars abundant in the Western diet can be quite detrimental to health.
Fat requirements for athletes are similar to those for nonathletic (20%-35% total daily calories should come from healthy fats). The International Olympic Committee does not recommend consuming less than 15% to 20% of total calories from fat because it is essential for many processes in the body, including cell membrane structure, absorption of fat-soluble vitamins, hormone regulation, brain health, and energy for muscle metabolism. Athletes should focus on good sources of fat that are high in unsaturated fats and essential fatty acids. Trans fats should be avoided, and saturated fat should be less than 10% of total consumption. Healthy sources of fat include salmon, nuts and nut butters, and avocado, as well as coconut and olive oil. Athletes may also consider taking omega-3 supplements as they can also counteract inflammatory and free radical formation sustained from training.
There has been renewed interest in eating high-fat, low-carbohydrate diets in low-intensity and endurance exercise. Fat, in the form of plasma-free fatty acids, intramuscular triglycerides, and adipose tissue, provides a fuel substrate that is both relatively plentiful and increased in availability to the muscle as a result of endurance training. The body cannot extract the energy from fats fast enough for high-intensity exercise, hence the high carbohydrate mantra for athletes. However, our bodies store thousands of calories of fats that can be metabolized at an adequate rate for energy during endurance exercise. Essentially, athletes use these diets to change their metabolism so their body will preferentially burn fat for fuel. This would be beneficial for ultra-endurance events to prevent some athletes from “bonking” or “hitting the wall” when their glycogen stores are depleted because of their metabolism being geared for burning carbohydrates versus fat for fuel. Athletes consuming less than 10% of their calories from carbohydrates are able to oxidize fat between 1.2 and 1.5 g/min during progressive-intensity exercise near 65% . A fat-burning adapted Ironman triathlete is able to use the fat stores in his or her body to fuel the race effectively at that oxidation rate for the entire race compared with a carbohydrate-burning athlete who would need to consume another 90 to 105 g per hour to maintain performance.
Studies addressing the effects of low-carbohydrate diets on the ease of weight control in athletes, the capacity to train and recover, immune function and injury risk, or hand-eye coordination or capacity to concentrate in sports are lacking.Additionally, some endurance athletes can be insulin resistant, and eating a diet high in carbohydrates may not be best for their long-term health. Some studies show that marathon runners with lower coronary risk factors have marked atherosclerosis.
Athletes stress many of the metabolic pathways during training and may have increased micronutrient (vitamin and mineral) requirements. Most athletes should be able to obtain sufficient micronutrients through a well-balanced diet, but athletes who practice extreme dietary or weight-loss patterns or eliminate whole food groups may be at risk for certain deficiencies. Examples would be restricting EI, vegetarians, illness, injury recovery, or those with specific medical conditions. Athletes should be evaluated on an individual basis if there is concern for possible deficiency based on symptoms or performance decline. Hence, there are no general micronutrient guidelines for athletes. Common deficiencies include iron, vitamin D, calcium, and some antioxidants such as vitamins E and C. Vegetarians may require vitamin B12, iron, calcium, vitamin D, riboflavin, and zinc supplementation based on their food preferences. It is important to note that micronutrients are important for optimum health but are not considered to have ergogenic properties.
Iron serves as a key component in oxygen transport via hemoglobin and myoglobin in energy pathways throughout the body. Female endurance athletes are the most common group of athletes with iron deficiency, although any athlete, including males, may become iron deficient. Iron deficiency can occur from many causes, including heavy menstruation, inadequate dietary intake, gastrointestinal losses, and training losses both intravascularly and via sweat. Most experts agree that athletes’ requirements for iron are greater than the recommended daily allowance of >18 mg for women and >8 mg for men. Furthermore, a female athlete’s requirement may be as high as 70% more than the average.
Vitamin D is an important fat-soluble vitamin that helps regulate many metabolic pathways in bone health, inflammation, and muscle function. Some studies have also shown decreased risk of stress fracture and positive effects in injury prevention and rehabilitation. Athletes requiring vitamin D testing are those with a history of stress fracture, signs of overtraining, muscle pain or weakness, and a lifestyle involving low exposure to ultraviolet-B (UVB).
Calcium is important for many metabolic processes, including bone health (with vitamin D) and muscle contraction, nerve conduction, and clotting functions. Low dietary calcium intake is often associated with disordered eating and low energy availability in female athletes, which is another factor leading to stress fractures and low bone mineral density in this group. The IOC recommends 1500 mg per day of calcium along with 1500 to 2000 IU vitamin D to optimize bone health for at-risk athletes.
During exercise, oxygen consumption in muscle can increase 15-fold, leading to production of free radicals (or reactive oxygen species) that overwhelm the antioxidant protection system. High concentration of these species can be harmful to many cellular tissues, although some reactive molecules such as hydrogen peroxide and nitric oxide may serve functions in cellular signaling and as secondary messengers in moderate concentrations. Athletes should avoid foods that may increase oxidative stress and increase foods that are higher in antioxidants such as vitamins C and E. Two examples would be the Mediterranean diet, which has a favorable effect on blood lipids and also protects against oxidative stress, and a diet high in fruits and vegetables, which raises plasma levels of antioxidants and protects against many chronic diseases. Vitamin C promotes collagen synthesis, facilitates glycogen storage, and may prevent exercise-induced oxidative changes. Vitamin E prohibits propagation of free radical formation. At high doses, vitamins C and E can be pro-oxidant, and large doses of vitamin E can also impede vitamin K metabolism and platelet function.
Proper hydration is important for optimized performance, prevention of metabolic strain, and thermoregulation during exercise. Athletes should have a proper hydration strategy before, during, and after exercise based on their specific needs and fluid losses. Most authorities support athletes losing <2% body weight during activity, as more than that decreases cognitive function and performance. Thirst is often not a good indicator of dehydration as an athlete can sometimes lose 1.5 L before thirst is perceived.
Athletes may lose anywhere from 0.3 to 2.4 L per hour of sweat, and rates vary widely based on environment, sex, body size, and length of activity. Sweat comprises water, sodium, potassium, calcium, magnesium, and chloride, so athletes should replace both fluids and electrolytes with their recovery strategy. Hydration guidelines are summarized in .
Nutrition During Injury Recovery
As a way to facilitate healing, nutrition is often neglected. Athletes may often decrease intake in fear of weight gain during the recovery period. Nutrition can be an excellent tool to help attenuate muscle loss; limit fat gain; aid in muscle, bone, and collagen synthesis; as well as manage inflammation. While it is possible that caloric expenditure will be less during recovery, energy expenditure may initially increase 20% if the injury is severe because of mobility modifications. For example, using crutches during immobilization uses 2 to 3 times the energy compared with walking.
Athletes need to monitor caloric intake to decrease the loss of muscle mass during periods of decreased activity. This is especially important with immobilization, which is associated with decreases in muscle protein synthesis and anabolic resistance. Athletes should consider protein sources such as lean meats, dairy, and soy throughout the day. Those sources along with whey protein are also high in leucine, which aids in muscle synthesis. Athletes should consider increasing protein intake during this time 1.2 to 1.5 times their usual level to help build healing tissue and limit muscle loss. Once athletes begin active rehabilitation, they may resume normal training levels of calories and protein. Athletes may consider consuming 20 to 30 g of protein after rehabilitation sessions as they would with normal strength training sessions. Limiting or eliminating alcohol is beneficial as alcohol can impair muscle protein synthesis. Creatine supplementation may also help attenuate muscle loss during immobilization, but more research is needed.
For bone healing and stress fractures, athletes should have adequate intake of calcium and vitamin D. For athletes with multiple stress fractures, clinicians should consider evaluating vitamin D and other laboratory studies as well as assessing female athletes for disordered eating practices. Zinc, vitamin A, vitamin C, and other micronutrients have a clear association with wound healing, tissue repair, and growth.
Although inflammation is a necessary response to acute injury and is needed in the first phases of healing, prolonged inflammation may decrease recovery, and athletes should consider a diet higher in omega-3 oils such as salmon, flaxseed, and chia seeds. Athletes should also look for foods high in vitamin C as it has anti-inflammatory properties and also has been shown to promote collagen synthesis. Foods high in vitamin C include citrus fruits, red and yellow bell peppers, dark leafy greens, kiwi, broccoli, berries, tomatoes, mango, and papaya.
In conclucion sports nutrition is a key component for optimizing training, performance, injury prevention, and injury recovery. Nutritional recommendations need to be individualized for each athlete; thus, clinicians should be well informed to help determine proper caloric, macronutrient, micronutrient, and hydration intake based on the athlete’s sport demands and training goals. An athlete’s RMR along with his or her weight goals (loss, maintenance, or gain) are used to determine training macronutrient levels for protein, carbohydrate, and fat ratios. Micronutrient intake or supplementation should be determined based on identified nutrient deficiencies and/or dietary restrictions (eg, vegan, vegetarian) to assist with injury prevention and enhance injury recovery. Educating athletes on how to effectively fuel and hydrate for training sessions and competition based on the concept of nutrient timing is important to maximize performance. A comprehensive understanding of sports nutrition is crucial for clinicians to provide individualized and optimized recommendations.
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