Energy Systems: What They Are and How To Train Them

The human body works in mysterious ways. So mysterious, that we rarely attempt to understand its many functions. One function it pays to understand is energy production.  When it comes to producing energy for movement, the human body uses three systems. Each system serves a different purpose and during movement they each contribute a percentage of the energy needed to produce that movement. This blog serves to help you better understand these energy systems and how they may affect your training.

What are they?

The first and fastest energy system is the Creatine-Phosphate or ATP-CP System. This refers to stores of energy within your muscles that are ready to be used in a fraction of a second. This system fuels our fight or flight response and acts immediately to provide your muscles with energy for a quick, explosive movement. A heavy single rep deadlift, vertical jump, or swing of a golf club are examples of movements that rely heavily on the ATP-CP system.  This rapid production of energy requires approximately 3-5 minutes to recover and perform again. However, as quickly as this systems kicks in, it will begin to sputter out around 6-10 seconds. As the ATP-CP system runs out of gas the…

… Glycolytic System takes on the majority of the workload. This system relies on carbohydrates, or rather glycogen, to produce energy. The glycolytic system will step in as the second responder in energy production and carry you for another minute or so. Riding a half mile on an Assault Bike, pushing a heavy sled, or swinging a kettlebell are examples of movements powered by the glycolytic system. If you have ever done any of the aforementioned exercises, you’ll understand when I say this burns. At such a rapid rate of energy production, this system produces a byproduct that inhibits muscle contraction. We recognize this by the weak knees and burning sensation you get after a kettlebell snatch test or half mile sprint on the bike. To remove this byproduct from the muscles the body turns to…

… The Oxidative System. This system is constantly working. As our glycolytic system begins to fail we pass the torch to the oxidative system, and it burns for a long, long time. Simply put, the oxidative system is breathing, and is the most sustainable pathway of energy production and burning fat. This is the only system that directly requires oxygen and it can power moderately intense exercise for hours. Whether out for a 1 mile jog or racing in an Iron Man, the oxidative system constantly replenishes energy to keep you moving. This system is also the key to recovery during multiple bouts of intense exercise. Take a set of heavy kettlebell swings for example. You may swing for 20 reps without laboring to breathe, but once you put that kettlebell down the huffing and puffing begins. This is your body’s way of restoring energy to the muscles in preparation for another set of swings.

How Does This Apply To My Training?

Now for the good stuff. How does this affect my training, my goals? Well, for starters it depends on what you want to accomplish.

The way I see it is, in order for these systems to work to your advantage you must begin with a strong aerobic base. That base is the oxidative system and is basically your endurance, your ability to put out work for an extended period of time. Without this ability you will have a very difficult time performing repeated exercise in the two shorter, more intense, systems. Now you may be asking “So should I be running a lot?”. Maybe not a lot, and definitely not just running. Unless you are training for an endurance event you do not need to spend too much time in this energy system. The oxidative system is the easiest for us to adapt to and therefore building a good aerobic base will not take all of your time and energy. Try mixing it up. Running, cycling, rowing and swimming are several low impact activities that will improve your aerobic capabilities. Start with sessions of 20-60min  1-2 x/week and evaluate your performance. If you struggle, keep working at it. If you don’t struggle, maintain your aerobic activity level. While a strong aerobic base is important, efficiency and metabolic stress are paramount for goals that include fat loss, muscle gain, strength, longevity etc. This is why training the glycolytic system is the best bang for your buck. (As discussed before, the glycolytic system carries the greatest workload from about 10 seconds to 1 minute and up to 2-3 minutes in trained athletes). This system is best trained with short bouts (30 seconds - 1 minute) of high intensity exercise. While these intervals may suck/burn they are excellent for improving performance, strengthening muscle, and burning fat; three things just about everybody is chasing. Perhaps the greatest advantage is seen between intervals, during recovery. This is when we call on the oxidative system (breathing) to replenish energy for the next interval, thus primarily burning fat for energy. Therefore, if we work with shorter rest intervals we will see a greater demand on the oxidative system and more fat burned.  

As for the ATP-CP system, the same rules apply. If quick powerful movements or sport specific power pertains to your goals, you want to spend a good amount of time working on this energy system. If not, it still may have a place in your training regimen. As we age, muscle mass and strength steadily decrease along with our ability to produce large amounts of force quickly. According to a study at York University’s Muscle Health Research Centre, between the age of 50 and 80 years, muscle mass and strength decrease 0.5-1.5% and 1.5 - 4% per year respectively. The same study suggests that your cells’ ability to produce energy decreases with age (.3-1.4% /yr after age 50) and that with exercise, each of these effects can possibly be reversed. Short bouts of maximal effort (e.g  3 to 5 sets: 1-2 reps heavy deadlift or heavy sled march) will yield the greatest stress at the cellular level building stronger cells and more powerful muscle even as we age. I suggest seeking advice and instruction from a coach before attempting any big lifts or heavy intervals, but do not shy away. Your body will thank you!

It is important to understand how your body produces and uses energy in order to optimize your training. We all know that we need to expend energy during our workouts, but it is how we go about it that makes all the difference. For example…

Mary Finn wants to lose 20 lbs before her 40th birthday while maintaining strength muscle mass. She is motivated and eager to get to work, but she doesn’t know the best way to go about it. She loves jogging and strength training.

The best bet for Mary is a balance of high intensity intervals, between 30 seconds and 1 minute, with 1-2 minutes of rest, following a strength training session.  On her “off” or recovery days, endurance work is best. Weekly conditioning schedule might look something like this:

  • High Intensity Intervals: 3 - 4 x/week (pick one)

    • 30 second Assault Bike sprints;  5 - 10 sets

    • Heavy kettlebell swings; 10 minutes - 30s On : 30s Off

    • Battle Ropes Tabata; 4 - 8 minutes - 20s On : 10s Off

    • Continuous Box Jumps; 10x Every Minute On the Minute (EMOM) : 10+ minutes

  • Endurance Training: 1 - 2 x/week

    • 30 min run: moderate intensity

    • 45 min Spin Class

Mike Smash is 26 years old and competing in a strength competition later this year. He will be required to perform a deadlift, press, and pull-up each for a single rep. Mike will be scored on the amount of weight he can properly lift for each of the three requirements.

For Mike’s very specific goals he will need to choose a training plan that is equally as specific. Along with practicing his form and becoming familiar with each lift, Mike will need to develop greater power and the ability to produce a large amount of force quickly.

Therefore, Mike needs to spend a good chunk of time developing his ATP-CP system, the first and fastest system of energy production.

Mike’s training schedule might look like this:

  • Monday

    • Deadlift: 5 x 1 - 3 (75-85% of his max)

    • Body-Weight Jump Squat: 5 x 5

  • Tuesday

    • Assault Bike Repeats: 5 x .5 miles

  • Wednesday

    • Single arm Press: 5 x 1-3 (75-85% of max)

    • Push-Press: 5 x 5 (50% of max)

  • Thursday

    • Recovery Day

  • Friday

    • Weighted Pull-ups: 5 x 1-3 (75-85% max)

    • Ab Wheel Roll-Out: 5 x 5-8

  • Saturday

    • Heavy Sled March 10 x 15 yards

    • Heavy Kettlebell Swing 10 x 10

  • Sunday

    • Recovery Day

Along with other supplemental exercises Mike will train his glycolytic system 2+ days (Tuesday/Thursday) to improve his recovery and support his heavy workload.

In conclusion, your training needs to be specific to your goals. If you want to burn fat and lose weight, strike a balance between high intensity intervals and endurance work. If you want to set a new personal best in the deadlift, train in short sets of maximum effort. If you want to be a well rounded athlete, improve performance, strength and endurance, you must take the time to develop each energy system. Stick to the systems best suited to your goals and waste less time and energy reaching them.