Will Running Make You Lose Muscle?

Most people actively avoid running on the general basis that…well…they don’t like running. Fair.

However, for a select few, they are interested in starting up a running routine, but are worried that it may effect their strength progress and overall muscle mass. Lifters in particular tend to be concerned that if they start running, all the hard work they are putting in the gym will be negatively effected.

Is this true? Will you lose muscle training running alongside a strength program? Will running negatively effect your strength progress? Here’s what you need to know.

(Need some running workout ideas? Check out this video!)

1. Running Does Not “Eat” Your Muscle

There’s an idea that persists to this day that running is inherently catabolic. Lifters fear that by adding running into their routine muscle mass will quite literally be “stripped away” from their body.

This is not true. Running in and of itself will not effect muscle mass.

The only real reason running would truly cause you to lose muscle mass would be if the addition of running into your routine caused enough energy expenditure that you were now in a calorie deficit. While that might sound bad at first, this is easily corrected. Just eat more. Not too hard right?

So long as you adjust your diet to the addition of running into your training there is nothing you have to fear about losing your hard earned muscle. If you wanted to you could eat even more to put yourself into a calorie surplus and build muscle while training running. The big takeaway is running doesn’t effect your muscle mass, but a calorie deficit will.

Additionally, it’s good to note that if you were to make running you’re only form of physical training you would see a decrease in muscle mass. This would not be due to the activity of running breaking down your muscles, but simply that running would not be a sufficient stimulus for muscle growth.

I believe running has gotten negatively branded with this muscle breakdown myth due to how many individuals feel post run. Described as feeling “flat” lifters will complain that they feel skinnier after a run, they don’t look as good in the mirror, and maybe they even weigh less on the scale. There’s a reason for this and it’s not because you lost muscle. On a run you are expending a lot of water, glycogen, and salts in your body. These are the exact “materials” that give your muscles that full “pumped” feeling. So while you may feel flat post run, if you take the time to fuel back up properly you’ll be back to your normal jacked self within the hour or two.

2. Will Running Effect My Strength Progress?

Okay. So you’re not going to be losing your muscle if you start running. What about strength?

This is where I would say running has the potential to screw with your training, it all just depends on what your goals are.

The basic thing to understand is that you cannot be a high tier runner, and a high tier lifter at the same exact time. The training requirements are too different from one another, and the energy demands to properly train both to a high level are near impossible to achieve regardless of your willpower. You have to make the decision of whether you value your running more or your strength training.

For those of you concerned with running effecting your strength progress here’s how you can find the proper balance between the two. For starters, if you are serious about adding running into your routine, I would use running as your sole source of conditioning and eliminate other conditioning sessions that you may already have. Adding running on top of existing conditioning, on top of existing resistance training is a good way to run yourself into the ground.

Additionally, it’s smart to put your running sessions either on your off days, or after you have already gotten your resistance training in for the day. That’s not to say that you can’t run before a lifting session, this just guarantees that you have maximal energy for your resistance training. Also, I’d keep the overall running volume lower if strength is your main focus. While a competitive runner could be running up to 6 days a week, I’d shoot for 3 to 4 sessions a week if lifting is your jam. That keeps your training load manageable and keeps you from getting too fatigued from running that it ends up effecting your training.

Good to note is that if you prefer running to lifting you can definitely still make progress in resistance training. It just may not be as optimal as someone who focused mainly on their strength progress. Don’t be discouraged that your resistance training will be meaningless if this is the case as resistance training is a component of any solid running program.

3. Genuine Concerns of Combining Running and Resistance Training

While running may not be as detrimental to your muscle as people may believe, I don’t want to make it seem like it’s not without it’s flaws. Running can certainly conflict with resistance training goals, and it’s not something I’d spontaneously recommend to a client that had goals to be a high level powerlifter. This is more so for people that have to complete fitness tests with running involved but want to keep lifting, or for those looking to switch up their training a bit and just have some fun. It all comes down to balance in the end, but here’s some conflicts between running and strength training you should pay attention to.

Unexpected Injuries: Adding running to your training will increase injury risk. That’s not to say you should avoid it and live your life in a bubble, because simply stepping outside is increasing your injury risk. However, you should understand that with enough running you may eventually turn over an ankle, catch a bad twist on your knee, fall and scrap yourself up, and any of this could derail your resistance training for a short period of time. Not a huge issue to worry about, but it can happen.

Energy Demands: As we talked about above, you do only have so much energy to work with in a given day. If the addition of running into your training is cutting into your bodies ability to recover you will be negatively effecting your strength and muscle building progress. Simply cut back on the running volume/intensity if this is the case and always be recording both your strength training sessions and your running sessions to properly track your progress and your bodies response to training.

Time Management: Something that may not be immediately obvious is training resistance training and running and the same time can take up quite a bit of your time. Even simple running sessions can shoot up to an hour long, and resistance training is usually in the hour to two hour mark. Combining the two could seriously test your time management skills and if it comes down to having to pick one or the other stick with what you prefer. Don’t stress yourself out trying to make an impossible schedule happen.

(For more on how you can train running and lifting check out this video!)


Matt Molloy

Matt Molloy

I'm a graduate the University of Pittsburgh with a major in Exercise Science. I’m a local guy (North Penn) and athletics has dominated my life. I've led teams in basketball, baseball, soccer, golf and my passion, long distance running. I've been strength training for 6 years with a focus in power-lifting but have recently stretched to strongman since joining the pride here at the Den. When I’m not in the gym I enjoy, spending time with my friends, music, and relaxing and playing some video games.