Does doing cardio make you lose muscle?

I want to set one thing straight before I get started here.

This site is designed around having a solid all round physique with large amounts of lean muscle and low-medium body fat levels, I am writing this from the perspective of somebody wanting to build muscle fast, not someone interested in running marathons or competing in the annual hot dog eating competition!

The question of whether or not cardio has a negative impact on muscle mass is really up in the air for lots of people. I for one know seasoned veterans with concrete beliefs that cardio burns muscle so they steer completely clear. This post will set things straight and help you understand the impact cardio has not only on your performance but also your reflection.

What does cardio exercise ask of your body?

Unlike resistance (weight) training, cardio exercise is traditionally based around repetitive bodyweight movements which maintain a medium to high heart rate for extended periods of time. What this means is that your body's energy output is more centred around entering a catabolic state (tissue burning) rather than the anabolic state we need to build muscle. 

To put really simply, when doing cardio exercise, energy is burnt in this order;

1) Carbohydrates (both stored and direct from foods)
2) Fats (from foods and as stored cells)
3) Proteins (amino acids from muscle tissue)

Points 1 & 2 above is where you should aim to be and aim to stay. It is at those stages where one can rapidly reduce their body fat levels while maintaining their hard earned muscle mass. 

It is point 3 above that causes all the headaches! This is where your body transfers into a state of mass catabolism just to maintain energy output levels. It has burnt through the energy assigned for standard exercise and now needs an external outlet to keep the ball rolling. The body begins to feed off its own muscle cells as a key source of energy.

When does this happen?

As a general consensus in the strength training industry, medium to high intensity cardio with a duration OVER the 1 hour mark is seen as an instigator for the body shifting into a muscle burning state.

Are there ways to get around this if long cardio can't be avoided? 

After training several professional footballers, fighters and other sport men and women I understand that long periods of cardio sometimes simply can't be avoided. So if that person was on a bulking cycle and their main priority was to gain muscle weight while maintaining their fitness levels, I would always recommend 2 things;

  • Carb loading 1-2 hours before cardio activity.  

By eating 1-2 large servings of complex carbohydrates, you are ensuring your first choice energy stores are at full capacity, the higher they are, the longer they will last.

  • Change your cardio workouts to short and sharp continuous circuits.

A method I use to measure my own cardiovascular fitness levels are by monitoring my muscular endurance and breathing capacity. Both of these are influenced by your 'heart rate' and the higher your heart rate the more energy burnt and more benefits you will receive.

So raising your heart rate to levels above 75% of your max and maintaining it there is one of the most effective fitness and fat burning tools.

Running on a treadmill for an hour will still require large amounts of energy but will take around 15-30 minutes before high enough heart rate levels are reached, the levels needed to improve your cardio fitness.

What if all I want is size, should I forget about cardio? 

A big fat NO here. Cardio exercise actually helps you build muscle by enhancing your recovery from weight training by promoting blood flow and oxygen transport to your muscles.

If you're skinny at the moment and fat loss isn't a priority, aim for 2 cardio workouts per week.

If you have a larger frame with a little excess body fat, aim for around 3-4 cardio sessions per week by replacing 1 or 2 weight sessions throughout the week with a full body circuit.

If you're one of those people who trains hard each day only to be sore the entire week because of it, try improving your fitness levels with short sharp cardio sessions, you will see incredible improvements in your energy and recovery times.

Reuben's favourite cardio workout! 

I've been living the fitness lifestyle almost all my life which means I like to get things done as fast and effectively as I can, we all live busy lives so I'm sure you know where I'm coming from.

To give you a brief indication of the level of fitness I need to be at throughout the year I must be able to complete;

1) Run 1.5 mile (2.4km) in under 8 minutes
2) Complete 110 pushups in 2 minutes
3) Hold a static plank/bridge for 8 minutes

So most of my cardio sessions are designed for functional strength and fitness in the form of circuit training.

Setting up a circuit:

Select 5 different training stations; here is an example;

EX-1) Barbell deadlifts
EX-2) Feet elevated pushups
EX-3) Standing dumbbell shoulder press
EX-4) Burpees
EX-5) Treadmill sprints

Start on EX-1 and perform nonstop for 45 seconds, then move directly (without rest) onto EX-2 and do the same.

Go all the way through to EX-5 nonstop and that is 1 set complete.

You start set 2 directly after finishing set 1 with no rest in between. This is a continuous nonstop circuit which you must complete 7 sets to finish.

All up you would have performed around 30 minutes of non stop cardio conditioning. You can make changes to exercises, tempo, load and timings later as your ability progresses.

I've got 2 questions for you so don't leave without commenting below!

1) How often do you do cardio exercise at the moment?
2) What type of cardio do you use and for what duration?

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  • Guest (Kimberly Edwards)

    urple">I love the information in this article. I am a little late in answering your question but I wanted to answer it anyway:)
    At the present moment, I am doing 2 hours of cardio 7 days a week.
    I bike and complete sprinting intervals outside and I used the stair climber, stepmil, elliptical, and the treadmill when I have to do cardio at the gym.

  • Guest (Clayton Stewart)

    Hey Reuben,

    Recently I have been doing cardio almost none. Mainly because I wasn't sure that it was benefitting me any.

    Just last night I read your article "Getting ripped while maintaining size" and everything it said about low intensity cardio I had experienced first hand. Now I've decided that any cardio that I'm gonna do is gonna be HIIT.

    Thanks Reuben,

  • Guest (Paul)

    Hey I have read your views on cardio and does it hold you back on size! Well my story is I train five times a week at thai boxing I had not done it for around a year, and all I was doing was lifting weights I got a nice shape but now Iv just stripped the weight off since iv gone back thai boxing I'd like to fit in weight lifting with my cardio sessions but I do not know how to slot it in? My training sessions with the Thai boxing are Monday 12.30pm till 2pm tues 7pm till 8.30pm wen 12.30pm till 2pm thur 6pm till 7.30pm fri 12.30pm till 2pm I would really like to continue to stick to this program and get in lifting weights as well to keep size I don't know where to fit it In ?? I think I will need some sort of supplement to keep the weight on ? If you could advice me I would really appreciate it.

  • Guest (Jamie)

    I'm lost here. You reference cardio and the dilemma with regard to burning muscle, yet you don't mention interval training.

    In fact, to maintain or build muscle, the vast majority of your cardio should be HIIT so I find it bizarre that not only is not mentioned, but the main body of this article should be based around it.

    To anyone who may happen to read this comment - unless you are specifically looking to build up your stamina for a sporting event i.e. Marathon or very active sports such as football (soccer), High Intensity Interval Training is the best way to lose fat (for those looking to lose a belly before summer) and also maintains muscle mass (for those looking to tone and get ripped) - basically it is ideal for the majority of women and men, either looking to slim down, tone up or remain fit whilst building muscle.

    It is also based around you pushing yourself against your own limits rather than set distances; thus being a very individual and adaptable method of exercising (as well as it being much more time-effective than regular cardio)

    PS - The quickest way to lose fat through cardio, is not to maintain a high level of intensity.

  • Guest

    I do cardio every time after a weight training session about an hour worth twenty mins on treadmill best effort then 20 mins on cross trainer then 20 mins on bike all best effort is this bad for someone who wants to get fitter and increase muscle size I do chest, back bis, core circuit training, shouldas tris,bis forearms,legs day off then all other again

  • Guest (Rob)

    Good article and agree with everything - I have a dilemma as i weight train 5 times a week and run 2 marathons (3:25) a year as well. Do i notice a reduction / gain in muscle when i train for marathons? No.
    I know everything you said makes sense and i agree with but it does not seem to make much difference in reality. off training i do 4 days of 45 -60 mins cardio and on marathon training i do 4 days of up to 3.5 hours cardio.
    People seem to think if you run you will end up like a skinny marathon runner. Not so, marathon runners are skinny as they dont do weights.

  • Guest (Mario )

    I want to loose the belly man. I'm a big guy and Im starting to develope everywhere except the belly I want to get bigger and cut up and loose the belly. Basically just want to loose the belly what can I do. I don't want to loose my muscle mass just the belly. Will running in the park help a mile a day or more. Help

  • Guest (verchelino )

    hi am turning 40 next year am very thin and short but i have little excess fat only in my belly now that am getting older i just recently started working out and tho i see a lot of improvement over all i still don't know the best way to get rid of the extra fat around my waist

  • Guest (Tommy)

    Just stopping by, nice article

  • Guest (Jennifer)

    I'm a 16 year old female, 5 foot 3.5 and about 117 pounds. I started running because a year ago I had high blood pressure and with the history of heart disease in my family I was really scared. Since then, I've conditioned myself to the point where I can run at least 2 miles a day, 6 days a week outside. I tend to switch up my runs (a fast 2 mile run one day, an easy paced 5 mile run a different day, etc) to keep me from getting to the point where my run is too easy. I got a Siberian Husky when I started running so I had a running buddy, and now I kind of have to run with her or she won't be very happy with me :) But I take one day off a week to prevent injury. I haven't injured myself since I started this routine so I haven't done anything different. I also do hill intervals every once in a while because I live right by a long 6 percent grade hill that is great to run on!

    I have just recently decided I want to start weight training as well... I've become a big fan of running and really want to find something else that's challenging to do as well. Are there any exercise routines that will allow me to run 6 days a week AND lift weights without injuring myself or losing too much weight?? I am kind of addicted to running and don't think I would be able to run less than 6 days a week and maintain my sanity but I really need a little more meat on my bones. I want to be HEALTHY and am willing to work slowly for a goal as long as I know I will make progress. If I have a specific schedule to follow I am able to take an hour or two out of my day for exercise. I wish I had the money for a private trainer but alas my family is not incredibly active and I'm a bit alone here... If you could help me find a healthy routine where I can gain muscle and run without overdoing it that would be wonderful!

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