It's Saturday morning. You're about to head out the door to run your favorite trail for an hour when you get called into work for the day. You cut your run to 30 minutes so that you can get to work on time, thinking that perhaps you will run another 30 minutes in the evening. You ask yourself, "Is it OK to break up one run into two? Will I still get the same benefit?" Excellent question.
Running double workouts in one day might seem pretty hardcore. While many competitive runners run twice per day to log a large weekly training volume, double workouts aren't solely for elite runners.
When to Try Running Doubles
If you run less than 30 to 40 miles per week, it's better to run just once per day. Running 5 miles all at once is better than running 2 miles in the morning and 3 miles in the evening. Longer single runs build endurance and make you a better runner.
Once your weekly mileage reaches a level at which your daily runs are averaging an hour or more and your weekend long run is 90 minutes to two hours, it's better to run twice per day at least a couple of times per week rather than extend the length of all of your runs. Of course, running twice per day takes more time, and makes it more difficult to recover between runs, so you will need to factor that in too.
Proper nutrition after your first run, including carbohydrates and protein, is important so you can recover quickly between runs. Consume 200 to 400 calories of carbohydrates and protein immediately after your first run so you can recover faster. Spread your two runs at least six hours apart.
The biggest advantage of doubling up is that it allows you to increase your training load while minimizing stress on your body and reducing recovery time. Both physically and psychologically, it's easier to run 4 miles in the morning and 6 miles in the evening than it is to run 10 miles (or even eight miles) all at once.
When Not to Run Doubles
The only time you don't want to run twice is on the day of your long run. Your long run should always be completed all at once, especially if you're training for long races, because there are specific endurance and metabolic aspects of the long run that can only be obtained by continuous running. For example, one of the purposes of long runs is to deplete (or severely lower) muscle glycogen, your stored form of carbohydrates. When you deplete muscle glycogen, lots of interesting adaptations occur, including:
- the storage of more fuel in your muscles
- a greater reliance on fat by your muscles
- an increased capacity of your liver to make more glucose for energy