Slight calf nggle when running on treadmill, don't get it when running outside

Im training for the London Marathon and had a knee acl reconstruction 8 months ago. Im back in training and going well however when I run on the treadmill after a weights session I feel a niggle in the top of my calf, like a potential strain, its been there for months, yet when I run outside upto 10 miles now on a sunday its not there.

Strange, anyone any ideas.

Don't do weights. 

Run outside.

Run on Sundays only.

Its upper body weights, I usually finish with some light cardio. Also how can i train for a marathon running once a week lol!!

Mark on the treadmill your legs and ankles don't really move from side to side at all, the absolutely flat bed of the treadmill isn't actually that good for you, without the natural flexing and movement that you get on the road or trail you just pound and pound onto the same points with no variation, hence the pain. I would leave it out and do some rowing or cross trainer for the cardio.

Mr Puffy makes a good point. Personally I don't like them.

If you can find streetlamps, it would be best to run outdoors. 

Great that you're running so well after the op.  Good luck.

Thanks for that.

why can't you run outside in the wek.......

I agree that the treadmill isn't the best surface to run on.  Stick to the outdoors for your runs and do some other form of cardio in the gym

Are you running with any gradiant on the treadmill, i fiind putting it up to 1.5% stops my knees aching on them.

I agree with FF- running with no incline at all on the tready certainly crippled me in the past- vary between 1- 2.5% and it cuts the monotony of exactly the same footfall over and over again.

ok thanks will try it with slight incline, been told that before actually that putting it up 1% replicates outside more.