Should I do cardio before or after weight training?

A question many ask is this: I like to get cardio out of the way or I enjoy cardio, so can I do cardio first? The answer depends on your goals.

Aerobic vs Anaerobic

I know we are starting off with some big words!

Some of the questions you may have asked in the past is “why can’t I do cardio before my workout and get it out of the way?” Or you may also wonder why HIIT is recommended for you to do instead of just a plain old treadmill workout.

In the following sections, I will explain all this to you.

Back to big words.

ATP And Other Fun Stuff

Your body needs ATP (adenosine triphosphate) as a fuel for your muscles to contract. Without ATP, no bicep curls..or squats for that matter. There are a few systems in your body that use ATP for energy, two of them are your anaerobic system (lactic acid system), and your aerobic system (oxygen system).

Anaerobic System:

Your anaerobic system breaks down glycogen (which is kind of the energy created from carbohydrates). Once glycogen is broken down, lactic acid is produced. You usually feel lactic acid after an incredibly fast sprint or after doing a burn-out set of squats.

This system is used during short, high intensity activities like sprinting and strength training.

The anaerobic system conversion: 1 molecule of glycogen = 3 ATP

The breakdown of this is that your body will be burning a ton more glycogen this way. The reason you’re so beat after a very intense weight training session or a session of HIIT is that you are using your anaerobic system which is absolutely kicking your ass!

Aerobic System:

Your aerobic system uses a bit more of a complex process to break down glycogen into ATP. Essentially it uses oxygen. We could talk about KREB cycles, and all that stuff, but I’m sure you don’t want to be brought back to your 11th grade science class.

This system is used during long duration, medium intensity activities such as jogging or rowing. This system begins to be activated around the 8–10 minute mark of a cardio session. This is why many feel better after jogging the first mile.

In the aerobic system, each molecule of glycogen is broken down into 32 molecules of ATP, which helps you have sustained energy.

The aerobic system conversion: 1 molecule of glycogen = 32 ATP

This makes the process of using energy much more sustainable, which is good for those who want to run long distance.

What is this not good for? Well..not good for burning your glycogen..which means you won’t burn your energy storage, so you won’t be burning your fat storage either.

Conclusion

The rule of thumb for most workouts is it takes about an hour to use up the glycogen stored in your cells and liver, after which your body begins to start burning fat as fuel.

So essentially, weight training will train your anaerobic system, but only if you do weight training before cardio.

There was a great comparison between the two types of systems you would be training, and it goes like this:

Think about burning fat like digging for gold. You have to get through layers of dirt and rock (muscle glycogen) before you can get to the gold.

Doing cardio first is like digging for gold with a shovel. Getting through a single layer requires 32 scoops to be removed. You’ll eventually see gold, but it will take a while.

Doing resistance training first is like showing up to the same dig site with a full on backhoe. Now only 3 scoops are required to get through one layer thanks to your diesel fueled machinery. Hello abs, goodbye fat!

So should you do cardio before or after your weight training? It depends on your overall goal. But I would suggest if you’re looking for fat loss, to stick with cardio after your weight training ;) 

To be basic, if your goal is fat loss and to get shredded you’ll want to do a 40–50 minute resistance training workout, followed by 15–30 minutes of cardio.