I believe that consistent exercise is vital for everyone’s health and wellbeing, and there’s nothing I love more than helping my clients find a workout plan that motivates them and helps them to achieve their fitness goals. There are many different ways to exercise involving cardio, resistance training, or a mixture of both, but as long as my clients enjoy their training and get the results they want, I’m happy.

In this blog, I’m going to talk about cardio: specifically, whether too much cardiovascular exercise can actually be detrimental to your health. There is a common misconception that cardio is the be-all and end-all of fat loss, and how long you spend on a treadmill correlates with your results. But this isn’t necessarily the best approach, and an overreliance on cardio can actually be counterproductive. Just like most aspects of fitness, there is a balance you need to strike, and your perfect amount of exercise won’t be the same as someone else’s.

What is cardio and why do it?

Put very simply, cardio is exercise that increases your heart rate. Usually, it takes the form of steady-state cardio, such as jogging, running, walking or dancing. There are many reasons to do cardio, most important of which is improving the functioning of your heart, lungs and circulatory system, both when exercising and at rest. But cardio also makes you feel good, as it releases endorphins that interact with your brain and trigger positive feelings in your body. What’s more, cardio is also a useful tool in fat loss, helping to create a lean, muscular physique.

However, before we go any further, there are a few myths about cardio, building muscle and fat loss which need to be debunked.

Muscle building and fat loss are two different things, and require different exercises to achieve. Muscle building requires two main factors: resistance training and being in a state of calorie surplus, which simply means consuming more calories than you burn. Resistance training, meanwhile, can involve bodyweight movements like press-ups and crunches, but also weighted movements. Either way, resistance training burns far fewer calories than cardio, which tends to involve the entire body, rather than isolating certain muscle groups with each exercise (eg. a dumbbell bicep curl just works the bicep).

Fat loss, on the other hand, just requires being in caloric-deficit, which means burning more calories than you consume. This is commonly achieved through a combination of dieting and cardio, although cardio is not actually essential, since we burn calories through our basal metabolic rate anyway. Cardio uses a lot of energy by working the whole body at once, utilising almost every muscle group, so when combined with a moderated diet, it therefore puts you in a caloric-deficit by increasing your energy output.

Does too much cardio burn muscle?

In a word, yes. But this will only happen when all other energy sources have been completely depleted, with your body using up muscle mass as a last resort.

Glycogen — a stored form of glucose that comes from carbohydrates — is by far the most efficient source of energy for cardio-vascular exercises, and it will always be used when available. However, after glycogen stores have been depleted, typically after 30-40 mins of cardio, your body will be forced to use less-efficient energy sources, which will drastically reduce your performance and cause fatigue more quickly.

If all usable fat reserves have also been depleted, the body finally resorts to its stores of lean muscle mass, putting you in a catabolic state. Physiologically, this means you will lose your hard-earned muscle mass and strength, and increase your risk of injury. It will also massively reduce your performance, and prevent you from achieving the strong, sculpted physique you likely started your exercise regimen to obtain.

This is why it’s important not to go overboard in restricting your carbohydrate intake if you enjoy doing long cardio workouts. Before starting, it’s a good idea to replenish your glycogen stores by eating some carbs, giving you plenty of fuel for your session.

Is too much cardio bad?

This really depends on what you mean by “too much” — your definition of “too much” cardio won’t be the same for Mo Farah, for example, unless you also run 130 miles per week! If you look at endurance athletes, you’ll notice certain similarities in their physiques. Their muscles are full of slow-twitch muscle fibres, which are much smaller in size, but have better endurance.

Bodybuilders, on the other hand, have a greater number of fast twitch muscle fibres. These are bigger and more powerful, but tire extremely quickly, and are designed for speed and strength, rather than endurance. Despite both athletes having very low fat stores, they have very different physiques, because the make-up of their muscles is different.

If you want to sculpt a ‘toned’ physique, the best way to achieve this is by combining elements from both resistance training and cardio.

Consistent Cardio is Key

The amount of cardio you should do depends on how much you enjoy the exercise, and whether you’re willing to perform it on a consistent basis. If you try to commit to lots of cardio without being ready for it, or without even enjoying it, you’ll struggle to stay motivated. Choose a cardio workout that works for you, and set smaller, more reasonable goals that you can work towards.

For example, a 15 minute jog or swim every day is better, and potentially more enjoyable, than one hour per week.⁣ If your goal is to burn fat and create a leaner physique, cardio is certainly going to help you achieve this, but there is an optimal level of exercise which is really up to you to discover. The type of cardio doesn’t really matter, as long as it’s one you enjoy and are willing to stick to consistently. Combining this with a suitable resistance program, like my Ballet Blast workout, is the type of action your body will require to achieve a lean, sculpted and supple physique with long-lasting results.