Sports Nutrition : Sports Medicine

Dr. L. Birendro Singh *

A match during 14th Dr Kanti Mukherjee Memorial Invitation Hockey Tournament 2012-13 :: Pix - Jinendra Maibam

Nutrition plays an important role in sports performance. Traditionally, athletes have eaten high - protein diets, believing that if they eat extra meat, they will build extra muscle. In fact, extra protein does not build muscle, only exercise build muscle. In order to build up, the athlete needs to perform resistance exercise such as push-up and weight lifting, along with wholesome diet. A high quality sports diet should include carbohydrate, protein, fats, vitamins and minerals.

CARBOHYDRATES :

Carbohydrates are important for all athletes. Weight-conscious athletes such runners and figure skaters, often stay away from carbohydrates believing them to be fattening. Carbohydrates are not fattening. It supply only 4 calories per gram as compared to fats, which gives 9 calories per gram. Carbohydrates can become flattening if eaten with fatty foods, such as butter on bread, gravy on potato. Carbohydrates are likely to be burned off rather than stored as fat. A daily sports diet should provide 60% to 70% of its Calories from Carbohydrates. Lack of Carbohydrate results in a low blood glucose level leads to feeling light-headed, uncoordinated, unable to concentrate and overwhelmingly fatigue.

Approximately 375 to 475 gm of carbohydrates are stored in our body. Of this, approximately 325 gm as muscle-glycogen, 90 to 110 gm as liver glycogen and only 15 to 20 gms are present as blood glucose. Since each gram of glucose gives 4 calories of energy, the average person stores between 1,500 and 2,000 calories of energy within the bonds of carbohydrate molecule. This is enough energy for a 20 mile run. Excessive fermentable carbohydrate, especially sucrose in the diet is a main cause of tooth decay. Moreover, excessive dietary sugar is believed to be involved in a variety of other disease process like diabetes, obesity, coronary heart disease. Carbohydrates serve several important functions related to exercise performance.

i) as a major source of energy ;
ii) to spare the breakdown of proteins ;
iii) as a metabolic primer for metabolism ; and
iv) as the fuel for the central nervous system.

FATS :

Athletes should reduce this intake of fatty greasy foods such as pastries, butter and ice-cream. The foods tend to fill the stomach and leave the muscle unfueled and also elevated blood cholesterol level. 20% to 25% of the calories in a sports diet can approximately come from fat. The high density lipoproteins (HDL) may protect against heart disease by carrying cholesterol away from the arterial wall and subsequently excreted by the intestines. Regular and moderate levels of aerobic exercise may increase the HDL level.

The functions of body fate include
(a) providing the body's largest store of potential energy
(b) serving as a cushion for the protection of vital organ and
(c) providing insulation from cold environments.

Fat content of the body constitutes approximately 15% of the body mass of males and 25% of females. Fat contributes about 50% of the energy if requirements during light and moderate exercise. In case of prolonged work or exercise, may provide more than 80% of the energy.

PROTEIN :

Eggs, milk, meat, fish are the sources of complete protein. Despite the beliefs of many athletes, there is probably no benefit from eating excessive amount of protein. Excessive intake of protein may be harmful because the metabolism of large quantities of this nutrient may place a strain on liver and kidney function. Protein content of the body constitutes approximately 12 % to 15% of the body mass. It is hard to specify the exact protein requirement for athletes, because their needs vary according to type of sports.

Protein requirement for active adult is 1.0 - 1.5 gm/kg body wt. /day and growing athlete, 1.5-2.0gm/kg body wt/ day. Protein requirements may be increased in explosive events. It's requirements are mainly due to three reasons,
(a) Protein Catabolism contributes towards fuel demands of exercise,
(b) a positive nitrogen balance or increase in muscle bulk due to heavy resistance training
(c) recovery needs that follow damage and efflux of muscle enzymes.

VITAMINS AND MINERALS :

Vitamins and minerals requirement for athletes are higher than sedantary and active counterparts owing to higher energy expenditure. Anti-oxidants like vitamin E, beta-carotine (Vit A) and vitamin C are recommended during intense training programmes in order to prevent free radical damage. However, antioxidants should be discontinued periodically to prevent accumulation in this body and potential toxic effects, especially fat soluble vitamins.

PRECOMPETITION NUTRITION :

The precompetition meal has several advantages, (a) to prevent hypogycemia (Blood Glucose level) (b) to prevent hunger feelings (c) to provide adequate fluids and (d) to provide energy for the muscles. An athlete should eat a 60% to 70% carbohydrate rich diet and drink additional fluids.

Carbohydrate loading is one of the more popular methods used by endurance athletes to enhance performance. Side effects of carbohydrate loading includes (i) the athlete feel too heavy, high cholesterol level, high urea nitrogen level, susceptible to diabetes and heart disease etc.

FLUIDS :

For top sports performance, athletes should drink adequate fluids. Fluids transport nutrients to and from the working muscle, dissipate heat and eliminate waste products. For optimal hydration, athletes should follow few guidelines.

(a) In order to prevent dehydration during training, the athletes should drink adequate fluid on a daily basis - (lots of water, juices). Athletes can determine whether or not he is drinking enough fluid by seeing his urination. Urine should be clear and copius. Dark-coloured, scanty urine is a sign of dehydration and a signal for the athlete to consume more fluids.

(b) Before an event athletes should drink extra water, juice and other fluid preferably 2 hours before the start of the competition. Because the kidneys require about 1 hour 30 min to process fluids.

(c) During an event, athletes should drink one cup every 20 minutes.

(d) After competition or exercise athlete should drink enough fluid.

The best recovery fluids include juices, because the juice replaces not only fluids but also carbohydrates an electrolytes.