It doesn’t matter how good you are—if you’re constantly gassed, you’ll never be able to showcase your skills. Playing at a high level continuously without getting tired sounds like a simple requirement, but it takes a special type of training to build this endurance.

For many young athletes, conditioning seems simple. They might go for a run a couple times a week and think they’re all set. But different types of athletes need different types of conditioning. When we exercise, we rely on different systems for energy. Knowing the importance of these systems and the role they play in conditioning can help you tailor your conditioning program to your needs and make you ferociously fit.

The Three Systems

Our bodies have three basic energy systems, which are essentially responsible for the flow of energy through our bodies—the alactic anaerobic system, the lactic anaerobic system and the aerobic system. How these systems provide energy involves a bunch of chemical reactions and substrates and science class stuff—you can read more about that here. For now, let’s just worry about when these systems provide energy.

There used to be a belief that each system had one specific type of exercise to which it contributed:

• Short periods of intense exercise relied solely on the alactic anaerobic system.
• Slightly longer periods of exercise relied on the lactic anaerobic system.
• Periods of exercise lasting from a couple of minutes to several hours relied on the aerobic system.

However, research is showing that each of these systems plays a role in contributing to all types of exercise.

The chart below shows how the three energy systems produce energy over time. (Note: The ATP-PC system is another name for the alactic anaerobic system.)

The three systems provide different amounts of energy at different times. The alactic anaerobic system supplies the majority of the energy for very short (0 to 10 seconds) intense bursts of exercise; the lactic anaerobic system supplies the majority of the energy for longer (up to 1 minute or so) intense bouts of exercise; and the aerobic system supplies the majority of the energy for continuous exercise that lasts more than 1 minute.

The three systems are tied together. Although certain systems do more work at certain times, if one system is inadequate or under-trained, all aspects of your conditioning suffer. For example, the aerobic system plays a role in pretty much any exercise that lasts beyond 1 second, so it’s important to not neglect it even if you play a sport—such as football—that doesn’t often require continuous exercise longer than 10 seconds.

Much of the intersystem relationship has to do with recovery. For example, the aerobic system is crucial to the ability to recover after shorts bouts of high-intensity exercise. Having a conditioned aerobic system not only allows your alactic system to replenish faster, it also does a better job of picking up the slack to produce energy during short bouts of exercise when your alactic system hasn’t had time to recover.

A 2002 study found that “VO2 max appears to be related to both an increased aerobic contribution to sprint-recovery bouts and the enhanced ability to resist fatigue during intense intermittent exercise.”

Translation? Athletes with better aerobic fitness perform better in short bursts of exercise than athletes with lower levels of aerobic fitness. “The more aerobically fit you are, the faster you can recover from short repeated efforts,” says Brandon McGill, sports performance director at STACK Velocity Sports Performance. “All of the systems are interplaying.”

You need to condition all of your systems no matter what sport you play. Specifically, the ends of the spectrum—the alactic and the aerobic systems—are especially important to overall performance.

“The most bang for your buck is going to be developing the ends of your system–your aerobic system and your alactic system,” McGill says.

If you’re someone who does only alactic system conditioning, you need to work in more aerobic conditioning. On the flip side, if you’re someone who does only aerobic conditioning—such as multi-mile runs—you need to work in more alactic conditioning. Focusing solely on conditioning one system and neglecting the others is not a smart idea for any athlete looking to perform at his or her best.

“Aerobic conditioning gets a bad rap for power or fast-twitch athletes and really is beneficial in that it’s useful for helping athletes recover from anaerobic efforts. The faster an athlete can recover between plays, the higher level they can perform play after play,” says John Mikula, exercise physiologist for the Department of Defense.

RELATED: Alactic vs. Aerobic: Could You Be Doing the Wrong Exercises

Beating the System

It’s important to condition both your alactic and aerobic energy systems, even if your sport mostly requires intense short bursts of exercise (like baseball or football) or mainly extended bouts of lower-intensity exercise (like cross-country).

However, it does make sense to tailor your conditioning to the specific energy system you’ll be relying on the most. What you have to do is examine the flow of the sport you play.

In sports that rely primarily on short bursts of activity followed by periods of rest—like football, volleyball and baseball—it makes sense to spend significant time training your alactic energy system. In sports that rely more on constant motion or running with little rest—such as cross country, field hockey and soccer—it makes sense to spend significant time training your aerobic system. And in sports that require a combination of short bursts of intense activity and running long distances—such as lacrosse and basketball—you might want to take equal time to train both systems.

The key thing to remember is you’ve got to spend time training both your alactic and your aerobic energy systems no matter what sport you play. Although you can favor training the energy system you think will be most heavily recruited in your sport, if you focus exclusively on that system, your overall conditioning and ability to recover will suffer greatly.

Examples of Alactic Energy System Conditioning

This type of conditioning should consist of intense bursts of high-intensity exercise for 4 to 8 seconds followed by 30 to 60 seconds of rest.

• Short sprints (10-50 yards) with 30-60 seconds of rest between reps
• Short agility drills lasting between 4 and 8 seconds (such as 5-10-5 Shuttle or T-Drill), with 30-60 seconds of rest between reps
• Short sled pulls, pushes or resisted sprints, with 30-60 seconds of rest between reps

Examples of Aerobic Energy System Conditioning

This type of conditioning should consist of low-intensity exercise performed for a long duration.

• 1- or 2-mile runs at  50 to 70% intensity
• Riding an exercise bike at 75% intensity for 20 to 40 minutes
• Swimming at 60% intensity for 20 to 40 minutes
• Running 1,600 meters or longer

It’s also a good idea to combine different types of training to simultaneously target both aerobic and anaerobic conditioning. Examples include interval training, where you perform a maximum-effort movement for short periods of time (6-12 seconds), immediately followed by several minutes of low-intensity exercise, such as a short set of 40-Yard Sprints followed by a light jog for a couple of laps around the track.