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Metabolic Pathways and Metabolic Conditioning – Cleveland Clinic Health Essentials


Metabolic conditioning can take your body from a crackling engine to a well-oiled machine. But the key lies in understanding your metabolic pathways.

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“Your metabolic pathways are the three main ways your body produces energy,” says Ernest Miller, PT, DPT, CSCS, physical therapist and certified strength and conditioning specialist. “How you target and train each can help you optimize your health and fitness.”

Dr. Miller explains the ins and outs of your metabolic pathways and how to use them to improve your fitness.

What is a metabolic pathway?

Like cars, humans need fuel to run. Instead of electricity or oil, food is our fuel. But a lot has to happen to that piece of toast before your body can use it to recharge.

Here’s how it works.

The cells of all living things contain ATP (adenosine triphosphate). ATP is a molecule that brings energy to the parts of the cell where it is needed. Digestion converts food into ATP. Then very small amounts of ATP are stored – like money in a bank – in your body. They can be used as needed. But since only a small amount is stored, your body relies on its metabolic pathways to create the rest of the ATP it needs.

“Everything the body does — from breathing to competing in professional athletics — requires ATP,” says Dr. Miller. “The body uses different metabolic pathways, or types of chemical reactions, to produce the right kind of energy to fuel different activities.”

Your the body has three different metabolic pathways:

1. Phosphagen system (ATP-PC system) for immediate energy

Phosphocreatine (PC) is a molecule in your muscles that can make ATP in the blink of an eye. It is also known as creatine phosphate (CP). And although the PC is available when you need it, there’s not much to do.

“You store a small amount of CP that you can access quickly for bursts of high-intensity exertion,” says Dr. Miller.

Think of your phosphagen system as your immediate energy system. It’s the take-home energy your body needs to pull away from an oncoming train. In weightlifting, it’s what you use to reach your one-rep max (the most amount of weight you can lift for one rep).

“High intensity movements that last between 5 and 10 seconds use this immediate energy cycle. Your body doesn’t have time to go through the other two longer metabolic pathways,” Dr. Miller adds. “Because PC is stored in your muscles, it is immediately available for use.”

2. Glycolytic system (anaerobic glycolysis) for short-term energy

To understand the glycolytic system, let’s break down the roots of the word.

  • Glycorefers to something sweet, as in glucose or blood sugar. Glycogen is the stored form of glucose in your body.
  • lytic” and “lysis” refer to the act of loosening or dissolving something.

“Anaerobic glycolysis breaks down sugar to fuel activity. Like PC, glycogen is stored in your muscles,” says Dr. Miller. “But glycogen takes longer to break down.”

After about 6-10 seconds of intense exertion, your phosphagen system PC has dried up. So for intense activities and exercises that last longer – anywhere from one to three minutes – your glycolytic system takes the lead. Think of the glycolytic system as your short-term energy system.

3. Oxidative (aerobic) system for sustained (or long term) energy

Any activity requiring endurance uses the oxidative pathway.

“Your body uses the oxidative pathway for anything that lasts longer than a few minutes. After three to five minutes of intense energy use, it will kick in,” says Dr. Miller.

Along with the oxidative (or aerobic) system, your body needs oxygen to produce ATP.

“The phosphagen and glycolytic systems are anaerobic, meaning they produce energy without using oxygen,” says Dr. Miller. “Without the need for oxygen, they can kick into high gear faster than the aerobic system.”

The oxidative system fuels activities such as 30 minutes on an elliptical machine or running a 5K or even a marathon.

“A marathon runner runs at a lower intensity than a 100 meter sprinter. While sprinters need a lot of energy quickly, they run out just as quickly,” adds Dr. Miller. “But endurance athletes can reach a steady state where they run at the same speed for miles. Their aerobic system isn’t as fast. But because the exercise is less intense, they are able to produce energy. energy at the same rate they use it – and last longer.

What is metabolic conditioning?

Now it’s possible – and beneficial — to train your body to use each metabolic system, a process called metabolic conditioning.

“Depending on your goals, there are reasons to condition your body to use one metabolic pathway more than others,” says Dr. Miller.

For example, playing American football involves short, intense periods of activity with rest between games. This is why American football players benefit when they focus on conditioning their phosphagen system (remember, immediate).

“Compare that to football players,” says Dr. Miller. “Football is continuous. It’s a 90 minute game. Athletes always run with very few stops. Football relies more on your glycolytic and oxidative systems. Different sports require better use of different metabolic pathways.

How to Include Metabolic Conditioning in Your Fitness Routine

The three metabolic pathways are like the three musketeers – when you train one, you train them all.

“There’s a misconception that you can switch between each system, but in reality they all work simultaneously,” says Dr Miller. “The difference is in what percentage of each system you use at any given time.”

Dr. Miller points out that a well-rounded fitness program will condition all three. But prioritizing one specific pathway over another can help you reach certain activity and fitness goals.

“If you want to run a 5K or do other endurance activities, your metabolic conditioning needs to be geared more towards using your oxidative system (long term). Whereas someone who wants to make gains by lifting weights might want to start conditioning the phosphagen system (immediate),” says Dr. Miller.

You do not know where to start ? Choose activities and exercises that tap into the metabolic system you are targeting. Pay close attention to your intensity level and the duration of your work and rest.

Formation of your phosphagen system

The keys to making this system work are:

  • Super short intervals (aim for 10 seconds).
  • High intensity effort. You should feel this is as hard as it gets.
  • Long breaks between exercises.

Tip: If you can sustain your intensity for longer, that’s not your max and you’re using the wrong system.

Here are some examples of activities that make your phosphagen system work:

  • Swim at full speed.
  • Weightlifting your maximum weight for one rep.
  • Wind sprints (running at full speed).

Training your glycolytic system

For this system, you want to feel like you’re pushing yourself, but you can still maintain a moderate-intensity workout for two to three minutes at a time. Aim for a brief rest in between.

Activities that train your glycolytic system include:

  • Basketball.
  • Circuit training.
  • Interval running (alternating faster running with walking or light jogging).
  • Tabata and other types of HIIT (high intensity interval training).

Training your oxidative system

Training the aerobic system should last much longer than training the other systems.

“You should take shorter breaks because the intensity is low enough to do repeat bouts,” says Dr. Miller.

Aim for a few hours each week. You can break this down by doing about 20-30 minutes of exercise, three to five times a week. Here are some examples of aerobic activities:

  • LIIT (low intensity interval training). It’s the softer cousin of HIIT.
  • Longer bike rides outdoors or on a stationary bike.
  • Swimming laps.
  • Starting a running program.

“If you’re just starting to exercise, start with slow to brisk walking. Build up to 20 to 30 minutes at a time,” recommends Dr. Miller. “As your cardiovascular fitness develops, walk faster. Then move on to alternating periods of walking and jogging. From there, you can transition to jogging for 20 to 30 minutes at a time.

If stationary biking is your thing, Dr. Miller says cycling has the added benefit of training all three metabolic systems.

  • Pedal as hard as you can with maximum resistance to target your immediate energy system.
  • Target your short-term energy system by pedaling at a brisk pace with resistance at a moderate level for two to three minutes.
  • Do not try resistance on the bike and cycle at a leisurely pace for 30 minutes to work your long-term energy system.

You do not know where to start ?

Before trying metabolic conditioning, Dr. Miller recommends consulting your healthcare provider.

“An annual physical exam can screen you for cardiovascular and pulmonary conditions that would prevent you from safely starting a new exercise program,” Dr. Miller advises.

If everything looks good, the next step would be to consult a fitness professional. Qualified fitness professionals include athletic trainers, exercise physiologists, personal trainers, strength coaches, and physical therapists.

“They can guide you because it’s important to tailor metabolic conditioning to your abilities and goals,” says Dr. Miller. “They can help you sift through all the noise, see where you are, what your goals are, and help you find a suitable starting point.”