Exercise physiology

Intro The very basis of exercise is dependent on the body’s ability to take up and utilise oxygen in order to produce energy. This unit examines the production of energy (ATP) and those factors that influence the uptake and delivery of oxygen to working muscles

ATP, ADP and AMP Energy for muscular contraction comes from the breakdown of ATP (adenosine Tri Phosphate) The three (tri) phosphate molecules are the key to the release of energy As a phosphate is split off, energy is released

ATP, ADP and AMP Why is it preferable to break down ATP in the muscle cells? Because the muscles are the site of action. It makes sense to break ATP down where it will be used The body however only has limited stores of ATP. The body needs a mechanism for the creation of a regular supply of ATP for muscular work? What might this be? Food break down to provide the fundamental components of ATP

Sources of ATP The nutrients we extract from food are used to produce ATP. These are: Carbohydrate Fat protein

1. Carbohydrates Carbohydrate is broken down into ________ and stored as _________ in the muscle or liver Carbohydrates are the preferred source of ATP and can be used to produce energy either with or without oxygen present glucose glycogen

2. Fats Fats are broken down into _____________ or _____________ Fats are stored in the body as ____________ Fats tend to be used in the chemical production of ATP during very sub-maximal exercise and increasingly during aerobic exercise triglycerides free fatty acids adipose

Proteins amino acids tissues Proteins are broken down into ____________ and are used to create ____________ Proteins are used as a source of ATP in extreme cases only Why? tissues Because it requires breaking down tissue

Chemical production of ATP Production of ATP at rest At rest ATP is produced in the presence of oxygen (aerobically) This process is called: Cellular respiration This process occurs in muscle fibres in the Mitochondria The production of ATP at rest uses a mix of carbohydrates (glucose) and fats (free fatty acids)

Why is it preferable to burn mostly fats at rest? So the carbohydrates are made available in exercise when they are the preferred energy source

Muscular contractions Chemical pathway is: 1/3 glucose Free fatty acids ADP + P TCA or Krebs Cycle CO2 Energy Muscular contractions ATP Heat Water

Equation Oxygen Glucose + free fatty acids CO2 + H2O + Heat + Energy

What happens to the CO2 produced? What happens to the water produced? It is breathed out What happens to the water produced? Breathed out as vapour but also lost via sweat This is a very efficient system for producing ATP. For every molecule of glucose or fat used 38 molecules of ATP are produced What would this ATP be used for at rest? Heart beating, breathing, skeletal muscle pumps, gut contracts

Production of ATP during exercise During exercise, production of ATP depends upon the energy system being used. This in turn will be governed by the intensity and duration of the exercise. ATP-CP system this system uses the ATP already stored within the muscles. The breakdown of ATP to ADP releases energy for muscular contraction ATP Stored Creatine Phosphate Energy ADP + P

What is the role of creatine phosphate within the muscles? Used to reform ATP from the broken down components of ATP. A theory is that the more stores of CP the more the ATP-CP, the more ATP-CP system can be used What might the advantages be of taking the dietary supplement creatine? To increase the stores of CP in the body, so this process can occur more frequently This system occurs without the presence of oxygen (anaerobically) and provides energy for intense exercise over 0-10 sec

b. Anaerobic glycolysis (Lactic acid system) Anaerobic means In the absence of oxygen Glycolysis means Breakdown of glycogen Anaerobic glycolysis is defined as the breakdown of glycogen in the absence of oxygen for energy production

The pathway of energy production Glycogen ADP + P Glucose Muscular contractions ATP Pyruvic acid Insufficient O2 Lactic acid

What are the consequences of the product produced at ‘D’ Causes fatigue and the ‘burn’ associated with high intensity, repetitive exercise This system provides energy over 30-120 seconds for high to moderate intensity exercise

c. Aerobic glycolysis (aerobic system) Aerobic means In the presence of oxygen Glycolysis means the breakdown of glycogen in the presence of oxygen Aerobic glycolysis is defined as the breakdown of glycogen in the presence of oxygen for energy production

Muscular contractions Aerobic Glycolysis pathway Muscular contractions Glycogen Glucose Pyruvic acid CO2 Energy Sufficient O2 TCA or Krebs Cycle ACETYL COA Sufficient O2 Heat Water Fats triglycerides Free fatty acids

Continued Initially this process uses blood glucose, followed by stored glycogen. This process produces 36 molecules of ATP for every molecule of glycogen used. This is the preferred system during aerobic exercise of moderate intensity, e.g. Running and swimming

For sub-maximal exercise such as walking, fats (as free fatty acids) are the main source of fuel for the aerobic system. Explain why. Because there is plenty of oxygen to break it down. Also it saves the carbohydrates for more intense work For prolonged exercise such as marathons, the main fuel source once again turns to fats. Why? Because stores of glycogen are used up Fats however require more oxygen than carbohydrates to produce the same amounts of ATP. What are the consequences of this for the athlete? They have to slow down to increase oxygen uptake

What happens when an athlete hits the wall? When an athlete ‘hits the wall’ there is a sudden decrease in the amount of glycogen used and matching rise in fatty acid usage. As a result, there is an increased requirement for oxygen to use fatty acids as a fuel for exercise. If they do not slow down, they will start to produce ATP anaerobically. Lactic acid levels will rise, causing a sudden decrease in performance