Running twice a day is an incredible way to build fitness, but as is always the case with increasing mileage, adding second runs heightens the risk of injury. To avoid injury, evaluating your personal level of preparation is important.
As a rule of thumb, most people who run under 50
miles per week do not need to add two-a-days, as doing so could increase
mileage too rapidly. For lower-mileage runners, increase mileage slowly, by no
more than 10% per week until you feel comfortable running 50-55 miles per week.
Once you have run at that mileage level for at least 4 weeks, you can consider
For runners who have properly prepared, there are many advantages to including two-a-days in your training plan. First and foremost, it is an easy way to grow mileage and increase aerobic capacity. If you are already running a lot, it can seem daunting to add more mileage. For most runners, adding two extra 5-mile runs per week is easier than fitting ten additional miles into already long daily runs. Including second runs, rather than increasing mileage in singles, is also a bit easier on your body because you have time to recover in between the two runs.
There is one major downside to two-a-days, though: running all your mileage in one run will improve your aerobic system more effectively than splitting your runs. For example, one 10-mile run is more significant for aerobic training than doing a 6-mile run in the morning and a 4-mile run in the evening. So, developing a high mileage training plan is a balancing act. The goal is to run the majority of your miles in singles, then if you feel you are ready for a bit more mileage you can add doubles to your schedule to get a little bump in training.
If you feel prepared to begin running twice a day there are a few notes to keep in mind.
Rule 1: Add two-a-days into your training schedule slowly
For the first 3 weeks, only do one double per week. Once you feel comfortable at that mileage, you may add a second. Most distance runners will never need to run more than three two-a-days per week, though extremely high mileage runners may do more.
Rule 2: You should not run two hard efforts in one day
Do not run a hard 10-mile run in the morning, then go out and hammer 800m repeats in the afternoon. Typically, the easier of the two runs should be no more than 5 miles and should be run at a comfortable pace.
Rule 3: The ideal amount of time to have in between runs is 6 hours
This allows your body time to recover from the first run before beginning the second.
Rule 4: You may run two-a-days on either workout days or recovery days
If you choose to double on a workout day, you may do the easy run either in the morning before an afternoon workout to wake up your legs or run an easy evening double after a morning workout, which shakes some of the tension out of your muscles. If you plan to run a two-a-day on an easy day, you will be able to get large amount of mileage while keeping the day relaxed. Both have advantages and you should work with your coach to decide when two-a-days are best for you.
Running twice a day is a great tool for runners looking to take a step forward in training as well as those who love running so much that once a day simply isn't enough! Just make sure you are prepared before adding two-a-days to your training schedule.