Experts say that running too fast during your "long runs" is one of the biggest mistakes people make when training for a marathon.

Conventional wisdom says runners should run their long runs about one to two minutes slower per mile than they expect to run on race day. But people sometimes find this is a fairly slow pace so they run faster, thinking it can’t be so bad to run at race pace or, say, 30 seconds slower than race pace. But running this quickly week after week may stress your body, even if you don’t notice it. Eventually, you can become injured or end up running a terrible race because your body is worn out by the time race day is here.