LEARNING OBJECTIVES 1.Am I able to explain how athletes manipulate their diet to enhance performance?
STARTER Discuss what you think athletes do to enhance their performance – What is legal and illegal? How can athlete’s adapt their diet to enhance performance?
DIETARY MANIPULATION PRE-COMPETITION Carbohydrate (CHO) Loading is a dietary strategy aimed at increasing the body’s glycogen stores prior to an event to improve performance time This involves a 10-day programme – High intensity exercise for 7 days before an event to deplete muscle glycogen stores – In the first 3 days a diet high in fat and protein is consumed to fully deprive the muscles of CHO, whilst on a reduced or tapered training load (this increases the activity of glycogen-synthase, which helps break down glycogen) – High CHO and fluid diet 3-4 days prior to the event along with low fat and protein consumption on a low training load (this loads muscles with glycogen) – More glycogen is able to be stored due to the increase in Glycogen-synthase
DIETARY MANIPULATION SUMMARY OF CARBOHYDRATE LOADING POSITIVE EFFECTSNEGATIVE EFFECTSUSERSLEGAL STATUS Increases muscle glycogen levels prior to competition. Quality of training may suffer with low glycogen levels. Athlete may gain weight due to water retention. Long- distance Aerobic athletes Legal
DIETARY MANIPULATION COMPETITION DAY CHO-rich meal 2-4 hours before an event tops up liver glycogen stores High volumes of food and fibre-type foods should not be consumed in the days leading up to the event (which can cause digestive problems) CHO should be avoided one hour before the event (which can cause a decrease in muscle glycogen stores) as this may cause rebound hypoglycaemia, which may actually decrease muscle glycogen stores and bring on earlier onset of muscle fatigue Consuming a chocolate bar 5 minutes before an event can actually provide an energy fuel during the activity
DIETARY MANIPULATION SUMMARY OF PRE-EVENT MEALS POSITIVE EFFECTSNEGATIVE EFFECTSUSERSLEGAL STATUS Muscle glycogen levels and liver glycogen stores are high. Glucose can be eaten just before exercise. If meal is eaten 15-45 mins before exercise it can cause early exhaustion. Games players and Aerobic athletes Legal
DIETARY MANIPULATION DURING EXERCISE Performers should consume frequent but small amounts of food or drink high in CHO during activity of 45 or more minutes (this replenishes vital glycogen stores and delay’s fatigue) There is less need to consume CHO during exercise if the duration is less than 45 minutes Examples of CHO food consumed during exercise include bananas, glucose tablets, gels and sports jelly beans, or the preferred CHO drink
DIETARY MANIPULATION FLUID INTAKE DURING EXERCISE The state of Hydration (water content) changes from at rest to different exercise conditions If you feel thirsty then you are too late for hydration Water intake during prolonged exercise reduces the risk of dehydration and optimises performance Dehydration will increase the temperature and with have a detrimental effect on performance (possibly leading to heat exhaustion) Hydrating the body before an event will help to prevent dehydration etc
DIETARY MANIPULATION SUMMARY OF FOOD/FLUID INTAKE DURING EXERCISE POSITIVE EFFECTSNEGATIVE EFFECTSUSERSLEGAL STATUS Consuming small amounts of carbs maintains blood glucose level. Feeling uncomfortable when exercising. Gastro problems may occur. Athletes performin g longer that 45 mins Legal
DIETARY MANIPULATION TYPES OF SPORTS DRINKS Hypotonic drinks have lower levels of glucose than blood (about 4% glucose). They are vital during prolonged exercise. Drinking 4-8g of CHO per 100ml solution every 10- 15 minutes reduces the risk of dehydration and provides a partial energy supplement Isotonic drinks promote fluid hydration and replenishment of glucose during endurance events of more than one hour. They have equal levels of glucose as the blood (5-7% glucose) Hypertonic drinks are suitable as a recovery drink post- activity as they have higher levels of glucose (19%). These increase dehydration, so should not be consumed during the activity, as water is needed to help dilute CHO as it is converted into glycogen/glucose
DIETARY MANIPULATION POST COMPETITION The body can break down and convert CHO to glycogen/glucose better within the first 2 hours of recovery (which speeds up recovery) Adding protein to CHO consumed in the first hours post- exercise may stimulate glycogen recovery rates in performers involved in several consecutive bouts of high- intensity activity over a period of days There is a 45 minute window of opportunity for optimal refuelling after activity (e.g. a meal or drink high in CHO and protein) CHO stores used up in short duration exercise can be replenished in a few hours (recovery will depend on the intensity and duration of exercise) If stores are depleted after long duration activity, then recovery will take longer (sometimes days)
DIETARY MANIPULATION SUMMARY OF POST-EVENT MEALS POSITIVE EFFECTSNEGATIVE EFFECTSUSERSLEGAL STATUS Liver glycogen stores are replaced within hours. Muscle glycogen replacement is much quicker during the first 2 hours after exercise. NoneAthletes using carbs for energy. Legal
PLENARY Discuss which of the methods of dietary manipulation you use – How effective are they for you? – Would you consider trying other methods that you have not tried already?