Home > Ask Our Experts > How to Stop Legs Becoming Too Muscular from Running?

How to Stop Legs Becoming Too Muscular from Running?

By: Scott McBride - Updated: 4 Dec 2012 | comments*Discuss
Running Treadmill Muscle Exercise


I run regularly, about 3-4 times a week running approx 6 miles each time on a treadmill, however I have noticed that my legs have become thicker and bulkier which is exactly the opposite to what I wanted to happen. I follow a low calorie and fat diet as I have had weight problems in the past. What am I doing wrong? Should I stop running to lose the muscle?

(S.M, 4 July 2009)


Giving up running is not the answer, as the benefits you get from running far outweigh any negatives, such as thicker and bulkier legs. However, it may be a good idea to take a break from the treadmill and try running outdoors instead.

It has been known for treadmills to cause muscle imbalances in runners because of the way they work. At first glance, it may appear as though the body is being put through the same exertions whether running outdoors or on a treadmill, but there are some crucial differences between the two types of exercise.

When a runner’s foot hits a treadmill, it is dragged back by the motion of the machine. There is no need, therefore, for the runner to create his own forward motion. That can mean the hamstring and gluteal muscles are underworked, while the quadriceps, calves, abdominal and hip flexor muscles get a full workout. Running outdoors means using a series of muscles to create forward motion, so the body gets a more complete and balanced workout.

Looking at athletes at the top of the sport can show how different types of running and training can alter muscle size. Sprinters have big, well-developed muscles that can deliver power quickly, while distance runners have more slender muscles that will keep working longer.

When switching from a treadmill to outdoor running, don’t expect to cover the same distances as easily. Remember, the hamstring and gluteal muscles will have been underworked on the treadmill and will now be asked to do a lot more. Running outside offers other challenges too, such as hills and the elements, so go easy and build up the distance gradually.

Those unwilling to run outside should not dismiss the treadmill out of hand. It can be a good way to burn fat and is useful when the British weather makes running outside a non-starter. Just be aware that the treadmill offers a different type of workout. There are certain drawbacks, but if a runner is aware of a treadmill’s limitations, it is straightforward enough to devise a training routine that will compensate for them.

You might also like...
Share Your Story, Join the Discussion or Seek Advice..
Why not be the first to leave a comment for discussion, ask for advice or share your story...

If you'd like to ask a question one of our experts (workload permitting) or a helpful reader hopefully can help you... We also love comments and interesting stories

(never shown)
(never shown)
(never shown)
(never shown)
Enter word:
Latest Comments
  • Tammy
    Re: The Women's Running Network
    Hi, also trying to find out if Swansea groups still going? Thanks.
    7 October 2018
  • Rach
    Re: The Women's Running Network
    Hi I live in the Wolverhampton WV8 area and wondered if you have any activities running close to me please? Thank you Rachel.
    3 September 2018
  • Ali
    Re: The Women's Running Network
    Hi Vic. Try Potters Trotters. They used to meet at Northwood years ago, but now meet at Staffs Uni on Tuesday and Thursday. They…
    30 August 2018
  • Cathryn
    Re: The Women's Running Network
    Is there a beginners club in Torquay for women over 50
    31 July 2018
  • VikingMermaid
    Re: The Women's Running Network
    Is there still a group in Dawlish (S Devon)? I used to run with WRN ca 10 yrs ago here (leader was Sarah, who was a real…
    26 June 2018
  • Vic
    Re: The Women's Running Network
    Hi, Any running clubs in stoke on trent? Northwood area? Trying to rehab and lose weight after slipped disc surgery last year.
    13 June 2018
  • Bigsare
    Re: The Women's Running Network
    Is there. A group in Exeter still and when and where do they meet please
    2 May 2018
  • Verity
    Re: The Women's Running Network
    Hi. I ran with WRN over 10 years ago and was registered with UKA. I am now trying to join another club. Can my link to WRN be…
    22 April 2018
  • JanieN
    Re: The Women's Running Network
    Ha, ha - predictive text! Passing my message on - thanks
    7 April 2018
  • JanieN
    Re: The Women's Running Network
    Hi there I’m looking to reconnect with the Swansea group but can’t find the details. Any chance of either padding my message on or…
    7 April 2018