Best Time for Cardio (According to Fitness Experts)

Morning or evening? On an empty stomach or not? Weights before or after? We answer the big questions about the best time for cardio


I recently posted a question on Facebook asking folks what they thought was the best time to do cardio. From the various responses I received, I concluded that everyone has their own perception of how and when to do cardio exercises but most of them are not even sure of the logic behind their perceptions.

Remember, your reason for doing cardiovascular exercises should be to burn fat, while preserving muscle. Burning up of the muscle for energy is a common ill-effect of long distance cardio—frequently seen in marathon runners. Just notice the build of competitive runners, and you will see that they are usually extremely thin and skinny, with hardly any muscle.

Before we get into the best time to do cardio, let’s first understand the basics.

What is cardio?

Running, jogging, walking, cycling, aerobics, cross trainer, and swimming fall under cardiovascular exercises. Technically, anything that forces the body to use its ‘aerobic’ system to acquire energy can be termed as cardiovascular. The American Heart Association [AHA] defines cardiovascular exercise as that which involves steady and repetitive movement of a person’s arms and legs. Others have defined it as an increase in heart rate. As the heart beats faster, the breathing becomes heavy, requiring more oxygen, which in turn burns fat.

The main reason behind cardiovascular exercise is to increase cardiovascular endurance. Nothing wrong with that except that most cardio freaks forget that there are more important components of fitness, which they are neglecting such as muscular strength, muscular endurance, power, flexibility, agility, speed, coordination, and balance.

When is the best time to do cardio?

There are several theories floating on the web about the best time for cardio. After researching this topic for a long time, I share my conclusions below, with valid reasoning. In a nutshell,

  • Do cardio first thing in the morning
  • On an empty or partially empty stomach

Do cardio first thing in the morning

Cardio should be done on an empty stomach first thing in the morning. This is the most common view around the world and I agree with it too. But understand one thing: carbohydrate in the body fuels high-intensity exercises like weight training and sprinting. Fat on the other hand is the primary fuel for low intensity cardio.

When we wake up in the morning, our body is depleted of carbohydrates as it has not had any fuel for the last 7 – 8 hours, while we were asleep. This is the ideal time to target fat with the help of cardio exercises.

Do it on an empty or partially empty stomach

If you consume any form of carbs in the morning before doing cardio, [a common practice is to eat a fruit] then the energy for the cardio session is going to come from the carbs you ate and not from the fat you’re trying to burn.

Here comes the twist… the problem occurs when the intensity of your cardio increases and the body needs carbs for fuel, which it does not have when you’re on an empty stomach.

Avoid eating carbs immediately after cardio

One more thing you need to remember is that you should not have carbs immediately after you finish your cardio session. Wait for at least 30 minutes after your cardio workout as the body uses fat during this time to recover.

How do you prevent the body from utilising muscle for energy?

The best way to prevent the muscle from going into catabolism is to consume a branched chain amino acid [BCAA] drink before your morning cardio session. BCAA supplements can be brought over the counter. These drinks will prevent the muscle from breaking down.

Not only are your carbs and protein stores low in the morning but your cortisol [stress hormone] levels are high too. This is another factor responsible for muscle breakdown. To counter these problems, add two more things to your drink: Glutamine and vitamin C tablet [it will quickly dissolve in water]. Want a further increase in fat burning and antioxidants? Add black coffee to it. This combo of BCAAs, glutamine, vitamin C and coffee will skyrocket your fat burning and at the same time prevent muscle breakdown.

If any of you are doing HIIT [high intensity interval training] or sprint training [which almost all of you should be doing], it is not to be done on an empty stomach as HIIT uses carbs as its primary fuel. And again, if you don’t have enough carbs in the body, the body will target muscle protein for fuel. But consuming BCAAs before HIIT is even more important because as the intensity goes up, so does the muscle breakdown.

Any high-intensity training [weight training and sprints] uses carbohydrates as the primary source of fuel and any low-medium intensity workout [cycling, jogging, brisk walking] uses primarily fat for energy. Both the activities have their benefits—you just need to balance the two.

What if you do cardio at any other time of the day?

Another response I got on Facebook to my question was: Can cardio exercises be done at any time during the day? Of course you can—and it will burn calories too. But as I explained above, you should be aware of whether the source of those calories is fat or muscle protein.

Do cardio exercises a minimum of 3 hours before your bedtime

So if, for some reason, you are choosing to do cardio in the evening, make sure you do it at least two hours before your bedtime and three hours after your last meal. And don’t forget to take the drink mix I recommended above.

Can you do cardio along with strength training?

Even before I discuss the next point, the answer to it is a BIG NO. If any trainer is suggesting that you do cardio before or after strength training, they are wrong. Don’t do it.

The amount of energy required for a good weight training session is tremendous. If you do cardio before weights, you have already wasted a large chunk of energy. Now you are not going to benefit either from cardio or from weights. Also, carbohydrate forms an important part of any pre-workout diet for a weight training program, and as I have already explained, consuming carbs before cardio will not help.

Similarly, right after a grueling weight training session, not only have you depleted all carbs [muscle glycogen] but also broken down your muscles completely. The anabolic window after a weight-training session is around 45 minutes. You need to rest and have your post-workout drink during that time and not do anything else.

Even if you want to do both cardio and strength training on the same day, do one of them in the morning and the other in the evening. In my opinion, three days of cardio in a week is more than enough.

What about cardio as warm up for strength training?

This is again a misconception. As I have explained in my article on the correct way to warm up before a workout, for any type of activity, you need to do the activity-specific or sport-specific warm-up which gets your body ready for the imminent workout. I encourage you to read that article for a better understanding of appropriate warm-up routines.

Finally, how much cardio is enough?

  • A typical cardio session should not exceed 40 – 60 minutes as anything extra leads to muscle protein breakdown.
  • The minimum cardio requirements for a sedentary individual should be three times a week for at least 30 minutes.
  • The intensity should be about 50 – 85% of your MHR [maximum heart rate]
  • Maximum heart rate= 220 minus your age. [So if you are 20 years old then your MHR will be 200].

A version of this article was first published in the December 2013 issue of Complete Wellbeing magazine (print edition).

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Akshay Chopra
Akshay is one of the most qualified and experienced health, fitness and nutrition consultants in the field. An athlete, coach, nutritionist, author and over all a defence forces officer and a former pilot - all rolled in one. A transformation expert, he is known for taking over those cases which most professionals have given up. He is the co-founder and Fitness Chief of one of the most research based gyms in the country "Body Mechanics" and just launched the Human Design School.


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