When Should You Do Cardio?

"So, when is the best time to do cardio?" This is a question that I'm asked all the time at the online and at the gym.

People seem to have this idea that there is one magical window of opportunity for getting in their cardio and that if they miss it, they're screwed.

In reality, though, there's no single answer to this question – it depends on your own personal circumstances.

But in this post, I'll outline four different scenarios in which you might want to do your cardio and offer some tips on how to make the most of each situation.

Stay tuned!

What Is Considered “Cardio”?

Technically, all types of exercise are cardio because they make the cardiovascular system work harder.

But generally, what people refer to as "cardio" is any aerobic activity.

That is, any activity that is low in intensity and long in duration.

Cardio activities typically raise the heart rate and breathing rate, and can include activities like walking, running, cycling, and swimming.

While there are many benefits to cardio exercise, it is not the only type of exercise that is important for overall health.

Strength training and flexibility exercises are also important for maintaining muscle mass, bone density, and range of motion.

The thing is, if your training plan is not structured properly, you might find yourself in a situation where your strength workouts are suboptimal in performance.

This is because cardio if done at the wrong time, can rob you of the energy that you'd otherwise use during your strength session.

Speaking of energy, let's have a look at how aerobic exercise is fuelled.

Fuel Demands

When it comes to fuelling exercise, the body relies on a couple of different sources.

These are carbohydrates, fats, and proteins.

Depending on the exercise intensity, the body will use a different type of fuel as the primary means of providing energy for continued muscular contraction.

During low-intensity activities (like aerobic cardio,) the body uses carbohydrates, fats, and protein.

Something to point out here is that the primary contributions come from carbs and fats, while protein has a pretty low contribution to fuelling the activity.

The thing is that as training intensity goes up, the body has to switch to carbohydrates.

In fact, carbohydrates are the main source of fuel during moderate to high-intensity training, such as weight lifting and other forms of strength training.

This is because fats can only be used for energy with the help of oxygen (aerobic metabolism,) and the metabolism of energy during high-intensity performance is anaerobic (without oxygen.)

That is to say, carbohydrates are the best fuel source for strength training.

And, cardio training slowly but surely depletes you of that fuel source, especially if you do HIIT-type of cardio, where you have intervals of high exertion.

When Should You Do It?

Now, first and foremost, we want to mention that you don't necessarily have to ditch cardio before strength altogether.

In fact, aerobic exercise can also be a great tool for warming up before a strength training session.

By increasing your heart rate and blood flow, aerobic exercise can help to prepare your muscles for the demands of lifting weights.

However, it's important not to prolong your aerobic exercise too much, as this can deplete your body of carbohydrates and hinder your strength training performance.

So next time you're getting ready to hit the weights, consider adding a few minutes of aerobic exercise to your routine, but don't make it a 50-minute treadmill session!

Instead, do your 5-10 minutes of cardio & warm-up routine (RAMP), go all-out on your strength training, and only then, after you're done with weights, proceed to your cardio session.

And if you're tired after your strength session, you can even do cardio on your day off!

Final Thoughts

So there you have it - cardio is a great tool to burn some energy and warm up the body, but it can rob you of carbohydrates, which are really important for strength performance.

This is why I advise all clients to only keep their cardio to a length of ~10 minutes before a strength workout and do longer aerobic sessions either after a weighted workout, or on a day off.

When do YOU do cardio, and why?