Develop Your Energy Systems: How To Train Harder For Longer!

Your body's ability to create and use energy is vitally important to your overall fitness. Here's how to train your energy systems for better conditioning and workload capacity!

Develop Your Energy Systems: How To Train Harder For Longer! banner

Your body is an amazing machine. It can adapt to a variety of stimuli, effectively getting stronger, faster, bigger, and more conditioned depending on how it's trained. Much of this adaptation, however, depends on the efficiency with which your body produces and uses energy, namely adenosine triphosphate (ATP).

ATP is a high-energy molecule which powers nearly everything you do, including exercise. There are three energy systems that produce ATP. Your body uses these energy systems to generate more ATP for different training types, intensities, and lengths. These are the phosphocreatine, glycolitic, and oxidative systems.


  • The phosphocreatine system is utilized during high-powered activity of short duration.

  • The glycolytic system is utilized when the phosphocreatine system runs out. As the name suggests, the glycolytic system utilizes stored glycogen to create ATP. This system engages during moderate-intensity activity of moderate duration.

  • The aerobic, or oxidative, system is slower to provide energy, but its supply is almost limitless. We use our oxidative system for low-intensity, long-duration activity.

Part of being a good athlete is being able to do more work for a longer duration. In order for the body to become a more-efficient machine, we have to train it. That's where these energy systems come into play. The stronger and more powerful your aerobic and glycolytic systems are, the more work you'll be able to do, the longer you'll be able to do it, and the quicker you'll be able to recover.

Here are five ways to train your energy systems and boost your overall results!

Cardiac Output

Cardiac output training is used to improve aerobic capacity, or your body's ability to produce energy using oxygen. Specifically, this type of training improves the central factor necessary for the aerobic energy system to function optimally: the ability to transport oxygen.

By training in a low-intensity zone of 130-150 beats per minute (bpm), the heart is allowed to maximally fill with blood during each beat. As a result, eccentric cardiac hypertrophy can occur. In other words, the size of the heart chambers will increase, thus allowing more blood (and oxygen) to be delivered to the rest of the body with each beat.

Consistent cardiac output training will result in a lower resting heart rate, lower working heart rate, and greater cardiac efficiency. In addition, because of the heart's ability to better deliver oxygen throughout the body, your aerobic system will be better utilized at every level of training intensity. The more you can rely on your aerobic system to supply energy, the less you'll feel fatigue and the better you'll be able to recover.

To train your cardiac output, you'll have to spend extensive time in that target heart rate zone of 130-150 bpm. Begin with 30 minutes of work 2-4 times per week and increase the volume at a rate of 10 percent per week. You can either do steady-state exercise—I prefer incline walking—or you can do tempo intervals with bodyweight, light implements, or running.

Tempo intervals work best when you work at 80 percent effort for 15-20 seconds and then actively rest for 40-45 seconds. The whole point of doing this, though, is to make sure that your heart rate stays in that target range of 130-150 beats per minute. So, the activity type is not that important as long as your heart rate is in the correct range.

Cardio output training can occur 1-5 times per week, depending on your fitness level and training regimen.

Cardiac Power

At the tissue level, training cardiac power will increase the strength and contractile abilities of the heart muscles, which will further improve oxygen delivery. Training this system will also improve your body's utilization of oxygen to produce energy within the working muscles. In other words, you'll improve your ability to use the aerobic energy system at higher rates of exertion.

Cardiac power intervals involve one- or two-minute work intervals at maximal, sustainable effort. Your heart rate should only reach maximum at the last half or third of the work portion of an interval.

Rest periods can be 2-5 minutes, or as long as it takes for your heart rate to get below 120 bpm before the next set. Begin with 4-6 sets of intervals and increase volume conservatively each week. Utilize running or full-body cardio equipment to perform these intervals.

Do 1-3 sessions of cardiac power intervals or lactate threshold intervals per week, depending on your fitness level and training regimen.

Alactic-Aerobic Intervals

Alactic-aerobic training is designed to improve your endurance during intense activities. The mitochondria of your cells are the aerobic energy factories in the body. To achieve the above effect, you need to increase their density in your fast-twitch muscle fibers.

Increasing mitochondria density will not only increase your body's ability to sustain high-intensity activity for a long time, but also your ability to recover from those activities. Your increased ability to sustain high-intensity training means you'll have better strength-training sessions because your fast-twitch muscle fibers can perform more work.

To recruit those fast-twitch muscle fibers, do 6-12-second bursts of maximum intensity activity like stair sprints or sled work. Rest 40-60 seconds, or as long as it takes to bring the heart rate back down below 140 bpm. Be sure to remain below that lactate threshold or else your work stops being aerobic.

Begin with 14-16 sets and add volume conservatively each week. Do 1-6 sessions per week, depending on your fitness level and training regimen.

Lactate Threshold Intervals

The goal of this training is described in the name. Lactate threshold training increases the threshold, or intensity, at which the body turns energy production over to its fatigue-inducing energy system—the lactate or glycolytic system.

By training at an intensity at or near—within 5 bpm—the lactate threshold, the body is forced to adapt to produce energy at its maximal aerobic rate. This increases the maximal sustainable power output of the aerobic system and increases the size of the umbrella of intensity under which any activity will then be predominantly fueled by the aerobic system.

If your body is better at using its aerobic system, you'll be able to do moderate-intensity activities without having to use the glycolytic energy system for fuel. The oxidative system offers a nearly endless supply of energy, which means you won't fatigue as easily if you can use it during tough exercise. The greater one's lactate threshold, the greater the contribution the aerobic system can make to high-intensity activities.

In order to increase your lactate threshold, you have to train slightly above it. Run or bike for 4-6 minutes at a high intensity and then rest for 3-5 minutes. Do these intervals for 2-3 sets. The length of each work period can be increased conservatively each week.

Do 1-3 sessions of lactate threshold or cardiac power intervals per week, depending on your fitness level and training regimen.

Lactate Power and Capacity Intervals

Until now, I've primarily discussed ways to increase your aerobic capacity. But, it's also important to increase how long you can stay in the glycolytic energy system and increase the rate of exertion while you use that system. During really intense exercise, you want to stay in your glycolytic phase as long as possible so you don't have to tap into your reserve stores of energy. The glycolytic system can produce a lot of ATP in a short amount of time, but it's not sustainable in the long duration.

To train lactate power and capacity—and increase the rate and power at which the lactate system can be used to generate energy—you need to produce a lot of work in a short amount of time. Training in this energy system requires your metabolism to remain high for a long period after exercise, which translates to better fat-loss results for your physique goals.

However, this form of training is extremely taxing on the body. A high volume of lactate power training, or a lack of recovery from it, can easily lead to overreaching or overtraining. Also, because the glycolytic energy system is the quickest to adapt and actually has the least potential for change, it is best not to continuously train this system throughout the year.

Training your lactate power and capacity requires maximum sustained intensity lasting 20 seconds to 2 minutes. High-intensity, full-body activities like compound lifts are ideal for this type of training. Because work periods are so difficult, rest periods should be at least twice as long as the work periods. If you don't take a longer break, the quality of your effort will decrease and you won't achieve the adaptations to optimal levels.

It's best to begin by doing something like sled pushes for intervals of 30 seconds of work followed by one minute of rest. Do this interval twice more and then rest for about 8 minutes. After 8 minutes of rest, perform another series of 3, 30-second sled pushes with one minute of rest between pushes. You can add additional series to these glycolytic training sessions, but don't do more than four.

Glycolytic training should occur 1-3 times per week, depending on your fitness level and training regimen.