Which one should I do first? Cardio or strength training?

This is a very common question I get from women and men alike, particularly those who generally perform cardio and strength training workouts on the same day.

The quick answer is simple: It depends on your fitness goals.

For instance, if you’re trying to improve your endurance and heart health, then perhaps do your cardio exercise first. On the flip side, if you’re looking to build muscle and gain strength, then definitely do your strength training first. Now, if your primary goal is centered on weight loss, the answer isn’t so cut and dry.

Truth is, the answer to the question of whether or not perform cardio exercise or strength training first is, in and of itself, somewhat complex. So, let me explain things a bit further. And I’ll start by briefly comparing the general metabolic responses to cardio exercise and strength training.

If you’re trying to improve your endurance and heart health, then perhaps do your cardio exercise first. On the flip side, if you’re looking to build muscle and gain strength, then definitely do your strength training first.

As you’re probably already aware, cardio exercise is one of the best ways to burn fat, improve heart health, and reduce the overall risk of chronic diseases. Even though the benefits are obvious, cardio can present somewhat of a hindrance to strength training. This is mainly related to how the body burns fuels during cardio exercise.

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Cardio is fueled by the utilization of fat, glucose (blood sugar), and glycogen (stored glucose), which represents the storage form of glucose found in muscle and liver cells.

Fat is a slow-burning fuel that requires the presence of oxygen. Hence, it’s considered “aerobic” in nature and the process of fat burning itself is known as “aerobic metabolism”. On the flip side, glucose and glycogen are more quick-burning “anaerobic” fuels capable of providing immediate energy in the absence of oxygen. Utilization of these fuels is known as “anaerobic metabolism”.

Whenever you initiate cardio exercise (or muscle activity of any sort) your body will preferentially burn glucose.

Where does it come from?

Well, if your pre-workout meal is comprised of any carbohydrate-containing foods, they’ll be broken down into glucose. If no carbs are present or if you work out on an empty stomach (fasted state), glycogen will be broken down and converted back into glucose.

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Now, as your workout continues through a duration of say 2-3 minutes, your body will start to transition to more of a fat-burning state. In this state, your fat stores essentially fuel your cardio workout. This is the inherent mechanism by which cardio exercise supports weight loss. But, the body will also continue to break down and burn some glucose as well.

This is where cardio exercise can present a hindrance to your strength training efforts, especially longer duration cardio that becomes progressively more intense. When cardio exercise increases in intensity you’ll start burning less fat, as the body will start tapping more into your glycogen stores. This is not a good thing, as glycogen is needed to fuel strength training.

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To further explain, I’m going to switch gears to talk about strength training.

If you follow my blog, you’ve probably noticed that I talk a lot about strength training in general. Also known as “resistance” or “weight” training, this type of training inherently builds muscle, which is an integral component of body composition. Having more muscle and less body fat is ideal, as the latter increases the risk of obesity and numerous chronic diseases.

Having more muscle also beneficially influences metabolism, which is the rate at which the body burns calories. The more muscle you have, the higher your metabolic rate meaning, over time, you’ll burn more calories at rest and during all types of activity. Thus, strength training is necessary for maintaining the muscle needed to fuel the fat-burning process.

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As with cardio exercise, the body preferentially burns glucose at the start of strength training or any exercises that involve the use of resistance. This’ll occur whether you use free weights, machines, cables, resistance tubing or even your own body weight. But, unlike cardio exercise there’s an almost sole reliance on glucose for fuel during resistance training, as it’s anaerobic in nature.

If you consider the general duration of glucose utilization (2-3 minutes) this should make a whole lot of sense.

Think about it.

Have you ever performed squats or pushups nonstop for more than 3 minutes? While this isn’t totally impossible, more than likely you haven’t. These exercises are completely anaerobic in nature and don’t require the presence of oxygen; therefore, performing them continuously over extended periods of time would be a difficult, though not impossible, task for the average person.

Given the fact that glucose is the body’s preferred fuel source during resistance training, what do you think will happen if you’re repeatedly tapping into your glycogen stores just prior to your strength workouts?

It doesn’t take a rocket scientist to see that this’ll significantly impair your performance.

You’ll likely lift a lot less and fatigue more easily due to diminishing fuel.

It’s like trying to floor a car on an almost empty tank.

So, hopefully, you’re starting to understand why performing cardio exercise prior to strength training isn’t at all ideal, particularly when you’re training to build muscle or gain strength.

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This might not present much of an issue when done from time to time. Problems arise when you make it a habit and consistently train this way over several consecutive days at a time, as doing so can cause glycogen to be depleted at a faster rate than it can be replenished through the diet.

This is an especially important point to consider if you follow a high-protein, low-carb diet, as restricting carbs will inherently keep your body’s glycogen stores low.

Now, if you’re looking to improve your endurance and heart health, this mechanism might not be as influential since lifting heavy weights and building significant strength aren’t necessarily your goals. But, if you’re one who regularly performs high-volume or extremely intense cardio workouts (running or cycling over long distances) I’d still caution against lifting weights after cardio, as doing so can potentially lead to muscle overuse and injury.

Related Article: Eliminating Cardio Exercise for Weight Loss?

And what about weight loss?

Well, as I stated before, the answer to this question isn’t so cut and dry. I will say, however, that when it comes to weight loss, a strong argument can be made that weight lifting prior to cardio workouts is the more effective strategy.

Recall my mentioning that strength training is generally fueled by glycogen. This essentially means that it’s a ‘glycogen-depleting’ exercise. If you’re trying to lose weight, this can really work to your advantage. Think about it. If there’s less glycogen available to fuel your cardio workouts, stored fat becomes more readily available to be burned as fuel.

This is a win-win since fat burning (and muscle sparing) is the goal of weight loss. This is why I generally recommend performing strength training before cardio exercise.

When it comes to weight loss, a strong argument can be made that weight lifting prior to cardio workouts is the more effective strategy.

And the rationale behind my answer doesn’t stop there!

A single moderate-to-high-intensity strength training session can elevate your metabolism for up to 12 hours, which means you’ll burn more calories during the cardio session that follows (and beyond).

So, there’s another strong argument for lifting weights before your cardio workouts!

Related Article: The Important Role of Metabolism in Weight Loss

In closing, I’d be remiss if I didn’t mention that I’ve simplified some pretty complex mechanisms with the goal of making the information easier to dissect and understand. I’m not a believe me and just do what I say kind of expert. Hopefully, that goal was achieved.

I also want you to bear in mind that regardless of whether you engage in cardio exercise or strength training first, numerous other factors can directly (and indirectly) influence aerobic and anaerobic metabolism including your current fitness and/or disease status, dietary regimen, gender, age, and even your levels of underlying stress.

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At the end of the day, know that your workouts will be most productive when you’re fresh and mentally alert, regardless of which activity you engage in first.

So, do what works for you!

Just get the workout in!

If performing strength training prior to cardio exercise just doesn’t excite you, then do your cardio first. If this is the case, I recommend taking in a high-carb protein shake, an energy bar, a handful of nuts or even a piece of fruit just before you lift. This’ll ensure that glucose is readily available to effectively fuel your strength workout.

Related Article: How to Lift Weights Without Bulking Up