The energy systems rarely work in isolation The body supplies energy continuously (hence ‘continuum’) as long as activity occurs. Which is the dominant energy system for: ▪ Marathon? ▪ Shot Put?
It is fairly easy to know the dominant energy system for the marathon and shot put, but other sports are not so easy. So we use the Energy Continuum to show how the body changes between the 3 systems for activities that exceed the limits of one or more systems, or for activities that experience changing levels of intensity.
Important note: ALL 3 ENERGY SYSTEMS OCCUR CONTINUOUSLY, BUT THE PROPORTION OF ENERGY PRODUCED BY EACH SYSTEM CHANGES AS THE EXERCISE CONTINUES. The intensity and duration of the activities is the main determining factor for which system is predominant.
= point at which a particular energy system is unable to provide energy e.g. PC threshold = When no PC left = approx 10 secs
Onset of Blood Lactate Accumulation i.e. The point at which the concentration of lactic acid in the blood rapidly increases. Normal value for rest or aerobic exercise= 1-2 mmol lactic acid/litre blood Above 4mmol = OBLA
When this occurs depends on the aerobic fitness of the performer Untrained = 50% VO2 Max Highly Trained = 85% VO2 Max Why? their increased ability to remove waste products and supply oxygen to working muscles.
Supply of oxygen can determine which energy system is predominant Also the various enzymes and food fuels (this will again depend of fitness levels)
The way energy is provided for a 1500m race are very specific – “The ATP-PC is the predominant system for supplying energy during the 1 st 10 seconds, after which the lactic acid system becomes dominant for the next minute. The Aerobic System takes over for the middle of the race when the pace settles. There is then a return to the Lactic Acid system for the final sprint finish.” Analyse how the energy is provided for the following activities (use the same format as given for the 1500m above) Hockey Game, Marathon, 100m sprint, Trampoline routine
As we know, HR stays elevated after exercise to help get the body back to its pre-exercise state = RECOVERY.
We know the term ‘Oxygen Debt’ but there is actually more to it so we use a different term: At the start of moderate exercise it takes a while for the aerobic system to provide energy, so anaerobic processes provide it. Oxygen Deficit is therefore the extra amount of oxygen that would be needed to complete the activity entirely aerobically. Oxygen Deficit
The extra oxygen taken in after exercise (see graph) is now known as: E.P.O.C. (Excess Post-Exercise Oxygen Consumption) Note: on the graph HR drops quickly when exercise stops but this recovery then slows. i.e. 2 stages to recovery
What happens to the following levels after strenuous exercise? PC Stores Myoglobin Lactic Acid Carbon Dioxide Glycogen Depleted All O2 used up Increased Depleted
So after strenuous exercise these all need to be returned to their pre-exercise levels. Some are done quickly: Alactacid Debt (the fast stage) Some are done slowly: Lactacid Debt (the slow stage)
PC - elevated metabolism => energy used to restore PC stores - takes 3 mins. to fully restore PC (50% restored in 30 secs) - takes approx 4 litres of Oxygen
Myoglobin - (transports O2 from capillaries to mitochondria in sarcoplasm ) - stores are emptied during exercise so the O2 consumed during EPOC replaces it. - Takes 1-2 mins. to fully replenish - Takes 0.5 litres of Oxygen (ie the surplus O2 produced by increased HR and ventilation during EPOC)
Lactic Acid - removed in 4 ways during this stage: - 60% converted to pyruvic acid => krebs cycle - converted to glucose and stored in muscles and liver - converted to proteins - removed via sweating and urine Takes up to 1 hour to remove all lactic acid
CO2 – elevated after exercise and needs to be removed. - 70% dissolved in plasma (carbonic acid) - chemoreceptors detect increased CO2/low pH and stimulate CCC and RCC. Therefore Q and respiratory rate remain high during recovery to expel CO2 through lungs
Full recovery of PC takes 3 mins. If doing speed work – allow full recovery. Active Cool Down – removal of lactic acid is quicker. Intensity of cool down depends on individual but moderate (approx 35%) is best. Monitor training intensities; then you can avoid OBLA and maintain quality of training. Warm Up thoroughly – reduces O2 deficit by increasing O2 supply to working muscles and ensure myoglobin stores are full.