Cardio Before or After You Workout?

Jan 15, 2018
Ashley Ann Lawrie

This is the ultimate dilemma in the gym: Do you jump on the treadmill before lifting weights or do you finish the workout with the treadmill? One helps you warm up before the workout, and one finishes the workout with a good amount of sweat. On the flip side of that, starting with cardio can tire people out and discourage them from lifting weights, while other people choose not to include cardio at the end because they are tired from weightlifting. So which one is the better option?

Quick disclaimer: including any form of cardio, whether it be LISS (low intensity steady state – see blog post here) or HIIT (High Intensity Interval Training – see blog post here), will always be good for your health no matter where you put it in your workout. Regular exercise that trains the heart and lungs will always serve you well in life. What we are going to present in this article is where cardio fits in with your body’s natural energy systems.

ATP-CP System – Explosive Energy

Your body has 3 main energy systems running at all times. The first is your explosive energy system, (or ATP-CP system in technical terms). This system breaks down the creatine in your body to burn ATP – your body’s energy molecule. It works for about 0-10s and doesn’t require oxygen to complete the reaction. This energy system is what the body primarily uses when doing things like 1 rep-max lifts. It is also used in sprinting and other fast events that require an immediate burst of energy.

The next energy system is your short-duration energy system (or the glycolytic system). This system is very good at breaking down the body’s sugar stores to give us energy. This system works for about 10s-2 minutes and also does not require any amount of oxygen to allow the reaction to occur. This is also where lactic acid begins to build up in the muscles. Breaking down sugar without oxygen – very simply put – is how we create lactic acid. This is the energy system our body uses for our single-set exercises. It is readily available as long as our body has glucose in storage – which we always do from our food and body processes like gluconeogenesis!

The final energy system is the long-duration energy system. We can use this system for energy for a limitless amount of time. As long as there is oxygen and fat stores available, this system will give us the energy to sit on the couch, go for a walk, and even complete a marathon.

Although all of these energy systems are usually always working, the ratio of explosive to short-duration to long-duration is always changing depending on the activity. So when you come in for a workout at Free Form and jump right into your set of squats, your explosive energy system will kick in to help you get those first few reps in. Then the short-duration energy system will pick up the rest of the sets once the creatine supplies are depleted. So at the end of your workout, chances are you have worked through most of your explosive energy sources, most of your immediate glucose stores and therefore the energy system that will support the end of your workout in the long-duration energy system.

So what does that all mean?

To return to our original dilemma of when to do your cardio, we can look at it from an energy-system perspective. If you jump on the treadmill and start running right away, chances are you haven’t consumed enough oxygen to get the long-duration energy system going to use that at the beginning of the run. So your body will burn through the explosive energy system and the short-duration energy system while your body increases its breathing rate to match it’s oxygen needs to its oxygen consumption. So when you get off the treadmill, now all you have to lift weights with is your long-duration energy system. It will work but you won’t get the same explosive energy for your lifts.

If your goal in the gym is to get the most from your weight lifting sessions, then from  a physiological stand-point putting your cardio at the end of your workout is best. If you are going to take your workout at a steady pace and the strength of your lifts is not a priority than you can easily get away with doing your cardio at the beginning of the session.

See our blog post on HIIT workouts and their benefits here and see the benefits of LISS here.Cardio Before or After You Workou

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