Energy Systems Interplay
Using your class notes / textbook / wealth of knowledge, explain the interplay of energy systems used in a sport of your choice. Below is an example of basketball.
For any activity, rather than considering the overall contribution of the 3 energy systems it is probably more accurate to consider the energy system contribution and interplay at various stages of performance by considering the key factors of intensity (how hard the athlete is working) duration (how long the activity has been going for) and availability of fuels.
Basketball
Walking onto the court uses the aerobic system to produce energy. The body is receiving sufficient oxygen to produce energy aerobically. Fats are the main fuel source for this.
At the tip off all three energy systems are activated. The tip off predominantly uses the ATP-CP system as creatine phosphate is already stored in the muscle. It is an immediate fuel supply for up to 6 seconds of high intensity exercise.
Nicole then sprints to get the ball after Tam produces a magnificent tip off. She is still using her CP stores and is working at 95% of her maximum heart rate. As Nicole sprints to set up the first zone position her CP stores are depleting rapidly. We are now nearly 10 seconds into the game.
Gary then runs up and down the court for 15 seconds of high intensity effort. The lactic acid is the predominant supplier of energy for this effort, as CP stores have been depleted, and a fuel source of glucose is being used.
After 30 seconds the aerobic system becomes the predominant energy supplier. Enough oxygen is getting into our blood to start producing ATP aerobically. Respiratory rate, tidal volume, stroke volume and heart rate all increase to increase oxygen delivery to the working muscles.
Quarter time approaches and Melissa desperately needs a rest. During this break her CP stores are being replenished. The cardio-respiratory system is now providing enough oxygen to work aerobically, as energy demands have severely decreased.
Intermittent Team Sport: Netball
Netball is characterised by repeated bouts of high-intensity action interspersed with periods of moderate activity and active rest (during play stoppages). When the whistle blows to start play al 3 energy systems start contributing, but most energy is derived from the ATP-PC system in the first 3-5 seconds. During the same time the lactic acid system is increasing its contribution to energy production, but is slower than the ATP-PC system due to more complex chemical reactions required to break down glycogen as compared to PC. If efforts above 85% max heart rate last for longer than 5 seconds, the lactic acid system will increase its contribution.
There is sufficient PC to “power” efforts for up to 10 seconds and following each explosive burst, this will be drained and deplete the ATP-PC system. Restoration of PC will occur at very low intensities but it is likely that until a 60+ second break occurs (quarter time) this system will not have adequate opportunities to totally rebuild/restore PC and increasing high intensity efforts will be driven by the lactic acid system as the match progresses, especially for mobile players such as centres, wing attacks/defence etc.
The aerobic energy system only supplies a small portion of energy during these initial intense efforts, but its contribution increases as PC has less time to resynthesise and the game progresses.
The aerobic energy system provides most of the energy needed during moderate activity during the game after the 30-second mark, and it is critical for efficient recovery between play stoppages and breaks. During a quarter, even if high intensity efforts are required, once the aerobic system has established itself as the major ATP producer (30+ seconds), it still contributes more to ATP production than the lactic acid system which despite increasing its contribution can only produce 1/5 – 1/7 as much ATP in total as the aerobic system.
i.e. at the 5 second stage the contribution from the 3 energy systems for a centre might be:
ATP-PC – 90%; LA – 5-7%; Aerobic – 3-5%
At the 60 second stage the contribution from the 3 systems for a centre might be:
ATP-PC – 25%; LA – 15%; Aerobic – 60%
Continuous Individual Activity: Marathon
The marathon is a continuous activity that lasts for just over 2 hours at the elite level. When starting, all 3 energy systems supply energy. PC will be used at a slower rate, as a marathon runner will not be running at maximal effort. Hence it will peak later, at about 8-10 seconds. The lactic acid and aerobic systems are also contributing to ATP production and from the first step increase their contribution, but because the activity will not exceed the lactate inflection point in the earl stages, the aerobic system quickly takes over as the major ATP producer.
During any surges in the race, where the lactic acid system increases its contribution, it still cannot produce the same amount of energy as the aerobic system (2-3 ATP compared to 30-36 ATP). During surges the lactic acid system isn’t the major ATP provider, rather it is the system that provides the extra energy required to allow an increase in intensity / work output.
Once PC is depleted it does not have a chance to replenish itself so the ATP-PC contribution is limited to the first few seconds of the race.
The aerobic system is not only important for producing ATP during the race but it also plays an important role in breaking down any metabolic byproducts that accumulate when the lactic acid system increases its contribution, as well as converting any accumulated lactic acid back into glucose to be used either aerobically or anaerobically.
i.e. at the 5 second stage the contribution from the 3 energy systems might be:
ATP-PC – 80%; LA – 15%; Aerobic – 5%
At the 1 hour stage the contribution from the 3 energy systems might be:
ATP-PC – 0%; LA – 5%; Aerobic – 95%