Which Energy Systems are Most Critical to the Repeat Sprint Athlete? ...Trick Question?
There are three energy systems which allow the body to produce energy.
While all three are important to athletes, it can be misleading as to which are the most important for the repeat sprint athlete.
Here, we discuss the demands on a repeat sprint athlete and determine the most critical energy systems these athletes should focus on.
What is a Repeat Sprint Athlete?
A repeat sprint athlete is one who is required to tap into a high level of power in a sporadic and repeated fashion while still maintaining a low level of fatigue. Think sports like football (AFL), soccer, rugby, basketball and mixed martial arts….in these sports an athlete may spend a great deal of the game jogging or standing on guard, preparing for action but when action is required – it is explosive, high energy and high-intensity.
These short burst of high intensity, full-body action may be required again and again and yet it is critical that the athlete maintain these actions without becoming fatigued from the very first minute to the last minute of the game.
So what systems most greatly affects the repeat spring athlete?
Let’s examine the energy systems and requirements for the athlete a bit further…
Three Energy Systems Explained…
The three different energy systems are as follows:
1. Alactic (ATP-PC) – Immediate Energy/ High Power, Short Duration
Adenosine Triphosphate (ATP) and phosphocreatine (PC) also sometimes referred to as the phosphagen system is an immediate form of energy that functions without oxygen. This energy system allows for approximately 12 seconds of maximum effort.
Alactic energy is the type the body calls upon when bursting into a sprint or pitching a baseball. These activities are explosive and typically involve full-body involvement. However, these are not activities that are sustained for long periods of time…
First, ATP supplies the energy…as ATP declines, the PC supplements then decline until there is a shift to a different energy system.
Think: 100m Sprinter
2. Lactic (Glycolytic) – Intermediate Energy / Moderate power, Short Duration
Once energy expenditure moves past the ATP-PC phase, it moves into the lactic phase. This is where dietary carbohydrates are utilized. Glucose circulates glycogen into the blood that may have been in the muscles and liver. It is then broken down through a series of chemical reactions called glycogenolysis.
It is estimated that glycolysis creates an energy expenditure of up to 16 calories per minute during this phase.
The lactic/glycolytic energy system helps to supply energy for approximately 30 seconds to 2 minutes. Once 2 minutes has passed, your body begins to move into the third energy system…
Think: 400m Swimmer
3. Aerobic (Oxidative) – Low Power, Long Duration
After your maximum efforts are fueled by the ATP-PC your performance declined and was fueled by the lactic system – finally as energy continues to be expended your body calls upon the aerobic/oxidative system.
The aerobic/oxidative system is dependent on oxygen and is the most complex of the three energy systems. This is the stage where the body starts to prioritize. With continued energy expenditure it understands the need for a recharge of ATP, yet it knows that first and foremost the most important thing to provide the system is oxygen. In this stage the body is performing a sort of ‘triage’, slowing down many of the systems that are not necessary for this continued performance and instead focusing on the ones that are necessary for ongoing endurance.
Unsurprisingly, these systems all operate via two components: power and capacity. Power, the speed at which the body can derive energy; and capacity, how long the activity can be sustained; are inevitably the defining features of conditioning as a whole and must be kept in the right balance for your sport.
But conventional wisdom on the subject of when these three different pathways are used has often been misunderstood.
It used to be thought that the first system (Alactic) drove the first 30 seconds of output, before the second (glycolytic) system kicked in for the next 90. It was thought the third and final system started up at the two minute mark, and thus sustained activity was considered a waste of time for the repeat sprint athlete.
What really happens?
All three energy systems start at the commencement of intense activity, and not in the staggered model outlined above. However, the extent of their contribution depends on the duration and nature of the activity itself. The aerobic system, whirring away in the background, is critical as the aerobic/oxidative energy system is actually responsible for regenerating the creatine phosphate that is used to fuel the high intensity sprint.
As such, current research suggests the aerobic system actually contributes a significant portion of that initial 30-second burst once thought to be the sole purview of the Alactic system: 13% in a 10-second sprint, and as much as 27% for a 20-second period.
So it’s easy to see the importance a well-developed aerobic system can have on a repeated sprint athlete.
Why that’s important:
Nobody wants to burn out fast on the field: you need to keep up a sustained and reliable performance for the duration of the game, and that means improving your aerobic capacity. The body relies more heavily on the aerobic system with each repeated bout of activity, such as during interval training. Therefore, if an athlete’s aerobic system isn’t properly developed and fails to provide this support, the body fatigues a lot faster when faced with repeat high intensity bouts of activity. Aerobic/oxidative training is about increasing your ability to recover your Creatine phosphate to allow you to sustain levels of high intensity activity for longer!
This means that most field based sports like football (AFL) and soccer are in fact an alactic-aerobic sport. The alactic system provides immediate energy to drive sprint-based activities, while the aerobic system is responsible for substrate recovery between bouts. The old thinking was that particular sports, the ones which relied on explosive energy, didn’t require aerobic conditioning.
In football, it might feel like you’re relying on explosive energy, courtesy of systems one and two as outlined above. But that performance is fuelled by aerobic metabolism, and to a greater degree with each successive bout. Those bursts of explosive power come from the alactic system, and they’re fuelled by creatine phosphate. That essential creatine phosphate would run out quickly… unless it’s being regenerated by aerobic/oxidative metabolism.
A game of football essentially involves a prolonged jog with regular sprint bursts of various types. That means available recovery time on the ground is minimal, and your body has to be able to sustain high levels of activity without allowing your power to drop. It’s a long game, and you’ve got to be ready to play ‘til the very end.
Not every sport requires the same level of aerobic capacity, so it’s important to build your energy systems appropriately to support your sport. But if you participate in a repeat sprint sport, the ability to excel requires a combination of both the Aerobic and Alactic Energy Systems.
Joel Jamieson - Ultimate MMA Conditioning