If you're tight for time, then splitting an 8 to 10 miler into two workouts once in a while won't hurt you. But as indicated above there is a pretty broad range of opinion--the rule of thumb (e.g., Pfitzinger) is that you don't really need to do doubles if you're under about 70 mpw--I'd modify that to 60 if you're a 6 day week runner.<br><br>
Nevertheless, there are physiological advantages to doing doubles that can offset the downside of not getting the full amount in. The physiologist Tudor Bompa suggests doubles for elite-level runners, and indeed most top level programs do suggest double workouts 5-6 days a week.<br><br>
For the more recreational runner, like most of us, who max out at 40-70 mpw, you're probably better off doing singles most of the time (I've re-thought that principal for high school age runners and masters runners, and see nothing wrong with those age groups putting in a few doubles a week to bump up the mileage, while not over stressing on singles). As indicated however, you don't want to sacrifice your long run (especially if you're a marathoner)--if you're scheduled for a 15 or 18 as your long run, then do it all at once.<br><br>
I've found that doing a shake-down run before or after a hard workout (say long intervals or hard tempo) is often better/easier than doing it all at once. Say you have a 4 mile tempo run, and you want to do 10 miles that day. Think about an easy 3-4 miler in the morning, and then you can get your workout in with a lot shorter warmup and cool down than if you did it all at once. This is especially beneficial on a hot day (or cold or wet...), when you're already dealing with the elements. Of course the downside is time to get dressed, and double showers, etc.<br><br>
Another rule of thumb is to space at least about 6 hours between your workouts; otherwise you're not fully recovered and you won't gain the benefits of a double.
Nevertheless, there are physiological advantages to doing doubles that can offset the downside of not getting the full amount in. The physiologist Tudor Bompa suggests doubles for elite-level runners, and indeed most top level programs do suggest double workouts 5-6 days a week.<br><br>
For the more recreational runner, like most of us, who max out at 40-70 mpw, you're probably better off doing singles most of the time (I've re-thought that principal for high school age runners and masters runners, and see nothing wrong with those age groups putting in a few doubles a week to bump up the mileage, while not over stressing on singles). As indicated however, you don't want to sacrifice your long run (especially if you're a marathoner)--if you're scheduled for a 15 or 18 as your long run, then do it all at once.<br><br>
I've found that doing a shake-down run before or after a hard workout (say long intervals or hard tempo) is often better/easier than doing it all at once. Say you have a 4 mile tempo run, and you want to do 10 miles that day. Think about an easy 3-4 miler in the morning, and then you can get your workout in with a lot shorter warmup and cool down than if you did it all at once. This is especially beneficial on a hot day (or cold or wet...), when you're already dealing with the elements. Of course the downside is time to get dressed, and double showers, etc.<br><br>
Another rule of thumb is to space at least about 6 hours between your workouts; otherwise you're not fully recovered and you won't gain the benefits of a double.
