Why do my legs hurt while running?

Why don't my legs hurt after running on a treadmill?

• Hi. I recently got a treadmill. I'm wondering if it's possible to run 'wrong' on a treadmill. For example, I just did an hour on there, I tend to go back and forth between difficult speeds and then slightly lower speeds, for recovery. I get really hot etc. but I feel like my legs should be ache afterwards or something... but they don't? A few minutes after I don't feel like I've done anything. I finished about fifteen minutes ago and my stomach feels really bad, however my legs feel totally fine. I think I must be doing something wrong, so yeah. I don't know what the speeds are in but I try to go up to 9, or else 8.5, then back down to 7 or 6.5. I can't remember how many miles I did. Maybe I'm not lifting my legs high enough or something?

• Answer:

  Nothing is wrong with that at all! As a matter of fact I would love to be in that position when I run for my Cross Country team! Legs begin to ache due to Lactate acid buildup in the legs. Frankly your body doesn't have lactate acids for when you run on your treadmill. That is a very lucky thing, and if I had that for my races, I could've finished in the top 5 each race.