Will running bulk up my legs?

Hi, i'm just a beginner but I have been running on my treadmill every morning Mon-Fri  for 20 mins at between 6-7 mph (mainly 7) for the last year or so and have noticed recently that my legs have started looking a lot thicker.

 Could this be due to the running or something else and if so would continuing to run/changing my technique slim my legs down again?

 Any help would be much appreciated.



  • I've always had sticky legs before. Even when I was fat I was fat around my stomach but my legs were like two sticks. Had never any problems with jeans not fitting around my thighs.

    Now after running for 3 years I can't fit most jeans on because they are tight around my thighs. I'm not saying I have bulky legs because I still don't. I just have so much more muscle.

    And I dont mind it to be honest. Love it.

    I dont think running on its own will make that much difference, altough it will have an effect. Of course it depends how much you're planning on increasing your running in the future.

  • Some people react differently to others - I reckon it would be unusual for running to bulk up your legs but you might get a little bit of muscle on them depending on what kind of exercise you were doing before - if any.    Coming from football my legs got a lot slimmer when I started running - and since taking up cycling have bulked up a lot more than when I was just a runner. 
  • Having come from MTBing 4 years ago, I find the thighs are not as thick, or the knee overhang so much. The calves maintain their size grown first with clipless pedals. I've got so used to the look of runners that non-exercisers' legs, all smooth, look like they've got some kind of wasting disease and I feel sorry for the owner. So to me, to think I'd rather not have runner's legs is akin to admiring heroin chic image
  • In my experiance, they don't "bulk up", they actually slim down, and become more toned, mind you, my legs were HUGE before I started running image
  • I have been running only a short time though have 2 years heavy work on a cross trainer (which is sortof the same idea image) and there is no doubt that my thighs are a lot less than they used to be.... I think that most people have a lot of fat on their legs so really you are just getting rid of the excess. I guess if you are an athlete from a different area.... the result might be different.
  • Lindsey, the only thing that's going to bulk your legs up with that amount of running is what you're putting in your mouth.

    Running will tone them but not add bulk - only heavy weights, really heavy weights and lotsa cycling will do that.

    I like SteveC's comment about feeling sorry for the owners of non-exercisers' legs!

    I used to do a lot of weights and when I started running my quad shape changed; overall they're slimmer now. But calves!! image given up trying to find a pair of zip-up boots that fit anymore!

  • Must admit, my ideas about what constitutes a 'cracking pair of pins' has changed slightly since I've become a runner!  No, running won't bulk 'em up, and there's nothing wrong with a bit of definition in the calves.  image

  • I already have muscular calves that i cannot do anything to slim them down. After running for more than 1 week I find that instead of sliming down it makes my calves thicker and bigger:(((
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