Recovery Following Exercise Objectives: Define EPOC Explain why there will always be an oxygen deficit Explain what the excess oxygen is being used for in the fast and slow replenishment stages

PCr, R.E.R, OBLA, VO2 max, ATP, PFK, ADP, EPOC? Acronyms game What do each of these acronyms stand for / mean? PCr, R.E.R, OBLA, VO2 max, ATP, PFK, ADP, EPOC?

EPOC What happens to an athlete’s cardiorespiratory system during exercise? Why? What happens after exercise? Why?

Following exercise… … regardless of the type of exercise performed, breathing rates will remain elevated during recovery. This is called the excess post-exercise oxygen consumption (EPOC)… …and it enables the body to replenish ATP and PC stores, remove lactic acid and restore muscle oxymyoglobin levels.

Excess Post-Exercise Oxygen Consumption (EPOC) EPOC is the total volume of oxygen that is consumed after exercise which enables the body to fully recover and return to its pre-exercise state. It includes the oxygen debt which is oxygen that is used to restore muscle ATP and PC, and remove lactic acid. It also includes the oxygen required to keep breathing and heart rates elevated, and the oxygen restored to muscle myoglobin.

Oxygen Debt An oxygen debt will occur… … when the body has exercised anaerobically, either at the start of any exercise before the aerobic system kicks in, during intense exercise lasting up to 3 mins, or when the anaerobic threshold has been exceeded. The oxygen debt is used to compensate for the oxygen deficit – the amount of extra oxygen that would have been required to complete the exercise aerobically. As aerobic respiration does not happen for the first 3 mins of exercise, a deficit will always occur.

EPOC and Oxygen Deficit can be easily shown on a graph of Oxygen Consumption during exercise: VO2 (L/min) Sub-maximal Exercise Recovery

It does not necessarily follow that EPOC will equal deficit, as extra oxygen is required post exercise to: Supply oxygen to re-saturate muscle myoglobin stores Supply energy for the increased cardiac and respiratory rates that remain elevated during the recovery phase Consequently the amount of oxygen consumed during the EPOC is greater than that which might have been consumed during the oxygen deficit.

The excess post-exercise oxygen consumption (EPOC) has two components: 1. The fast replenishment stage (alactacid debt) 2. The slow replenishment stage (lactacid debt)

The fast replenishment stage This is the first component of the oxygen debt that is replenished and requires up to 4 litres of oxygen. Within this component, the very first amount of oxygen consumed is used to resaturate myoglobin with oxygen. The rest of the oxygen is required to produce sufficient energy from aerobic respiration to restore the muscle ATP and phosphocreatine stores It takes a short amount of time (2-3 mins) for this to be replenished This means that after a short (<10s) bout of intense work, the body will be sufficiently recovered after 3 mins to repeat the exercise

Interval training plays on this quick replenishment of phosphagens Training can increase muscle PCr and ATP stores.

The Slow replenishment stage (Lactacid Debt) Can take up to 2 hours and require 5-10 litres of oxygen which is used to do 4 main things: 1. Maintain the elevated heart and respiratory rates 2. Remove lactic acid from the muscles Most (65%) LA is converted into pyruvate and oxidised into CO2 and H2O through aerobic respiration – this requires oxygen! Typically this process of lactic acid removal takes approx 1 hour, but it can be accelerated by a cool down which ensures a rapid and continuous supply of oxygen to the muscles

EFFECT OF COOL-DOWN ON LACTIC ACID REMOVAL REMOVAL OF LACTIC ACID FOLLOWING EXERCISE cool-down continues to provide oxygen to skeletal muscle which therefore enhances oxidation of lactic acid and ensures that less lactic acid remains in tissue and there is less muscle soreness

The Slow replenishment stage (Lactacid Debt) 3. Replenish muscle glycogen stores: This depends on the type of exercise performed and the amount and timing of carbohydrate consumption following exercise Continuous endurance activity: little glycogen replenishment immediately after exercise, and can take up to 48 hours High intensity short duration exercise: significant muscle glycogen replenished within 30-60mins and all within 24hrs Due to conversion of LA back into glycogen via cori cycle Replenishment occurs much more rapidly if a high carbs meal (200-300g) is consumed within 45-60mins after exercise – the carbohydrate window

The Slow replenishment stage (Lactacid Debt) 4. Meet the increased metabolic demands associated with an elevated body temperature A 10˚C rise in body temperature doubles the rate of metabolic reactions Body temp doesn’t change this much, but metabolism does speed up meaning more oxygen is required!

Task: Exam Questions Q1- Outline the function and process of the fast component of the recovery process. (4 marks) Q2- The Graph shows the oxygen consumption (VO2) of a subject during a period of rest, sub maximal exercise and recovery. a) (i) State which letter (A–F) represents oxygen deficit and which letter (A–F) represents EPOC. (2 marks) (ii) How long did the exercise last and what does letter F represent? (2 marks) (b) EPOC consists of fast and slow components. What are the functions of the slow component and how are these functions achieved? (3 marks)

Q1- 4 marks for 4 of: A. EPOC explanation – volume of oxygen consumed in recovery above the resting rate B. The alactacid/alactic (debt/component) C. Re-saturation of myoglobin/haemoglobin with oxygen D. Re-synthesise ATP/PC levels E. Uses 2-4 litres of oxygen F. Completed in 2-3 minutes G. 50% PC stores replenished within 30 seconds/75% within 60 seconds A – NOT repay oxygen debt A – NOT removes lactic acid Allow a few minutes

Q2- (a)(i) 1. Deficit . B; 2. EPOC . C. (Credit first two letters only) 2 marks (ii) 1. Duration = 14 mins; 2. F = steady state/period when VO2 remained constant/consumption = requirement/supply and demand. (Do not credit VO2 max/max VO2/plateau) (b) 1. Slow. extra oxygen needed; 2. For removal/breakdown of lactate/buffering; 3. For supply to/maintain breathing muscles; 4. For supply to/maintain heart muscles; 5. Lactate mainly converted back into pyruvate; 6. Oxidised to CO2 and water; 7. Produces ATP (to credit must link back to 6 or 7) 8. In inactive muscles other organs (liver); 9. Some lactate converted to glucose/glycogen/protein; 11. Some excreted in urine and sweat. 3 marks

Homework: Revision for exam next lesson. Complete the key terms sheet with detailed explanations for each term AND Produce detailed, neat, colourful revision notes with diagrams. 2 sides of A4 max.