Why do I get random bruises on my legs after a hard run?

You get spots that look like bruises, except they don’t hurt?
I don’t know, I’ve never heard of anything like that. Might want to ask your doctor about it.

A bruise is a superficial internal bleeding, just under the skin, right?
If I may be so bold as to blatantly speculate something up: if running causes that in your legs, without hitting anything, then maybe you have a problem with thin veins that burst easily when your blood pressure rises. I get nosebleeds in warm weather for that reason.
Have you ever ran a lot in summer time? Do you know if heat makes the symptoms stronger?

When I was younger and was running 5 miles a day, this happened to me one winter! I never did find out why it happened.

Might be some sort of vitamin difficiency causing your capilaries to be weakened. Have you been taking aspirin?

I suspect that your random bruises are actually small hematomas caused by small veins being ruptured in your legs. They most likely will decease as your body adapts to your hard running over time.

I would not mess around with unusual bruising. Get a diagnosis someplace other than Fluther.

Thanks guys, I am goin to make an appointment….I think it is just the small veins bursting thing. Sounds so horrible, but I dont really think it is anything serious. I did an advanced spin class last night, woke up with a huge bruise on the side of my knee. I dont think my body is as ready as my mind for the level of excersize Im doing. I take advil, and recently was sick a couple days so I also took Thera-Flue wich has aceteminophine in it for pain releif. I am going to start taking a complete women’s multivitamin I think.

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Are you sure you are not hitting yourself without realizing it? I am not trying to be funny. Maybe you are knocking into the machines, and just brusing easily, rather then bruises from seemingly nowhere. Anyway, your doctor can check your platelets and a couple of other things, to make sure nothing is really off.