I commute to work which is 3.5 miles away by running in every few days. I was wondering if this was enough with the occasional longer evening run on the way back to train effectively for a half marathon without having to run a single distance of 10 miles at a time?
Running twice a day versus once a day can be something of a divisive issue among runners. There are certainly pros and cons to each option. Running twice a day means
- You can boost your mileage, if you don't have anywhere near enough time on certain days to do a run of your target distance.
- It can be beneficial if you need to recover from a hard workout earlier in the day, just to get your legs moving.
- In certain cases, doing two smaller workouts on a certain day can make speed training more effective.
That said, there are some things to be cautious of:
- For newer runners, doubling is likely too much of a stress on bones and muscles.
- Substituting two short runs isn't going to be nearly as effective as your weekly long run (e.g. 8 miles in the morning and 5 in the afternoon won't give you as much of an aerobic workout), which is crucial for longer races.
- You need to make sure you're not just running junk mileage. I have, on occasion, used an extra morning run as a short shakeout, but I still focus on making it a quality run.
It's been said that running twice a day shouldn't be done until you're running more than 50 miles a week. I think I agree with that; if you average 7-8 miles a day, splitting up the mileage isn't going to get you runs with any extended aerobic benefit. The runners I know who double regularly are at about 70-80 miles a week, and usually opt for something like 3 in the morning and 8 in the afternoon (I've personally never felt the need to double below 60). That said, I know folks who do 70-80+ miles a week but only run once a day, and seem to have similar results for distances 8k and up (still on the shorter end of long-distance running).
To make a long story short, yes, you can run twice a day when training for longer races. If you're doing half marathon training, you're probably at (or going to get to) that 50-60 mile per week mark, so doubling may be feasible, especially if you've got a tight schedule. However, it's not a good idea to do it more than a couple times a week, and it definitely shouldn't be a substitute for most of your longer aerobic workouts.