Nutrition for Exercise and Sport Energy Systems Applying the Principles of Nutrition to a Physical Activity Programme

Session aims Identify ATP as the energy currency Revise the characteristics of the three energy systems:  Fuels Duration Intensity Describe the contribution of different fuels in ATP production at different exercise intensities: Carbohydrates Fats Proteins (gluconeogenesis) Creatine phosphate

ATP: The energy currency High energy compound essential for muscle contraction Cannot be stored, therefore a continual supply on demand is essential ATP can be made by three energy systems

Energy systems – complete the table Fuel Duration Intensity Considerations CP Lactic acid Aerobic system

Energy systems – summary Fuel Duration Intensity Considerations CP Creatine stored in the muscle Sections Maximum The potential duration of this system is dependant on the individual’s fitness level and training Lactic acid Glycogen stored in the muscle Minutes Moderate − High As above. Through training we are able to increase the capacity of this system. This enables us to work at a higher intensity for longer and extend the duration of this system. Aerobic system Predominantly fat with the assistance of carbohydrates Ongoing Low − Moderate Fitness level and effective fuelling will effect an individual’s aerobic capacity.

Contribution of different fuels in ATP production Carbohydrate and fat are used to produce ATP Exact proportions depend on the conditions Protein is not normally used to produce energy unless glycogen stores are low. Protein from muscle can be broken down to release glucose for energy (gluconeogenesis) Creatine phosphate – present in small amounts inside the muscle can also be used to generate ATP for high intensity exercise

Fat or carbohydrate? Carbohydrate is stored in in the liver and muscles in the form of glycogen. Fat used during exercise comes from fat stored all over the body underneath the skin, and needs to be transported to muscles by the blood Carbohydrate and fat are usually used in combination High intensity, anaerobic exercise of short duration will predominantly rely on carbohydrate, as fat cannot be used in the absence of oxygen Aerobic exercise will use different mixtures of fat and carbohydrate depending on the intensity

Exercise for Nutrition and Sport Eating for Energy Applying the Principles of Nutrition to a Physical Activity

Learning outcomes Describe where carbohydrate and fat are stored on the body and in what quantities State the role of both muscle and liver glycogen Explain the onset of gluconeogenesis during prolonged exercise List factors that affect glycogen storage Describe how long glycogen stores can last List strategies to maximise glycogen stores Provide guidelines to ensure effective fuelling and refuelling for exercise

Stores of carbohydrate (glycogen) Energy stores Stores of fat (adipose tissue) Stores of carbohydrate (glycogen) Liver =60 – 100g (240 – 400kcals) Muscle =200 – 400g (800 – 1600kcals)  Total = 1040 – 2000kcal Body Weight = 60kg (female) % Body fat = 20% (i.e. very lean) Weight of fat = 12kg or 12,000g Fat kcal = 12,000 x 9 (9kcal per gram of fat) = 108,000 kcal

Glycogen stores Glycogen stored in each muscle cell is for the exclusive use of that muscle cell and cannot be transferred Liver glycogen stores are primarily reserved to maintain blood glucose levels If blood glucose falls the brain stimulates hunger in order to obtain fuel, or triggers glycogen breakdown During prolonged exercise the brain stimulates the use of amino acids from muscle tissue to convert to glucose - gluconeogenesis

Factors affecting glycogen storage Time of day (glycogen will depleted first thing in morning & after exercise) Fitness/training level (trained muscle better at storing glycogen) Lean muscle mass (more muscle = more glycogen storage capacity) Diet (consistent high carbohydrate intake is essential to replenish glycogen stores)

How long can glycogen store last? Moderately hard activity glycogen stores will last approximately 60-90 minutes Normal day-to-day activity: 4-5 hours

Strategies to maximise glycogen stores Pre training Ensure you top up your carbohydrate stores every 4 – 5 hours. Eat small regular meals to reflect your activity levels throughout the day. Aim to consume most of your kcal when you are more active Do not go for long periods of time without eating. If you are very hungry you tend to consume the wrong type of food. Do not exercise on an empty stomach, i.e. first thing in the morning. Aim to consume a light meal up to 2 hours prior to training or a larger meal 2 – 4 hours prior to training. Aim to consume low GI foods throughout the day to ensure a steady supply of carbohydrate energy. High GI foods may be beneficial immediately prior to activity to provide an immediate supply of energy.

Strategies to maximise glycogen stores During Activity If your activity/training session lasts more than 90 minutes ensure you consume carbohydrates during the session. Aim to consume approximately 20g of carbohydrates every 30 minutes.

Strategies to maximise glycogen stores Post activity After exercise consume enough carbohydrates to get your stores back up Consume them as soon as possible after your training session has finished The window of opportunity to refuel after exercise lasts up to 2 hours Research suggests that 15mins post‐exercise is the optimal time to refuel Females aim to refuel with 40–50 g of carbohydrates. Males aim to refuel with 60–80 g of carbohydrates Be realistic with the duration and intensity of the training session. If your session is low intensity and of short duration your refuelling requirements will be lower