I did something over the weekend that I've never done in training before. I split my long run in to two different runs: Five miles in the morning and then my 5K race, for a total of 8 miles.

When it comes to the issue of splitting up a long run, people tend to feel very strongly about if/when it's OK.

The purpose of long runs is to get you used to being on your feet for a long period of time and to simulate race conditions. In a race you don't get to run 10 miles, then go do something else for several hours, and then go run the rest of the race.

So for your really important long runs, you should do them in one session. Runs like your first 10 miler for a half marathon or your first 20 miler for marathon training qualify as those important runs.

However, I'm a big believer in flexibility in training plans, so I think it's OK to split up long runs in certain situations:

If it's a cut back week and you have a schedule conflict, I'd say it's OK to split up your run.

If you want to race a distance shorter than what your training plan calls for, it's OK to race and then add on the extra miles.

If you're in taper, and either a schedule conflict or a race comes up, go ahead and split up your run.

The idea here is that you don't want to make splitting up runs the norm. You should only split up runs on rare occasions, when you're really in a bind. And if you're training to win a race, win an age group award, or are in general very hardcore about your running, I recommend not splitting up your runs ever. If you're a more casual runner, who likes to race for fun, then allow for some flexibility from time to time.

When do you think it's OK to split up a long run?