Is Running Twice a Day Worth It?
The benefits of "doubling."
One of the questions I got recently was:
“On a scale of 1 to 10, how would you rate running twice a day for recreational runners?”
My answer?
A 10.
This isn’t because everyone needs to run twice a day. Most people don’t. But if your goal is to gradually run more without beating yourself up, I think it’s one of the smartest tools you can use (and one I personally use often).
Here’s why.
Most people think there are only two ways to increase running volume:
Add more days of running each week.
Make your existing runs longer.
Both work. But both also have limitations.
Maybe you’re already running as many days as your schedule allows. Or maybe you strength train on your non-running days and don’t want to give those up (as you shouldn’t). So the obvious alternative is to make each run longer.
That works... until it doesn’t.
The problem is that your body often tolerates increases in single-run distance much worse than increases in total daily or weekly volume.
That’s why I’m such a fan of doubles. Instead of forcing one 10-mile run, you might run 5 miles in the morning and another 5 in the evening. You end up with the same daily mileage, but each individual run stays well within what your body is adapted to handle at the moment.
This idea lines up with a study I wrote about last year for the Run Long, Run Healthy newsletter. The researchers followed more than 5,200 runners across roughly 588,000 runs to figure out what actually predicted running injuries.
Weekly mileage increases weren’t the best predictor of injury.
Instead, what mattered most was how much longer your longest run became.
Compared with keeping your longest run within 10% of your previous longest run, increasing a single run by:
10–30% increased injury risk by about 64%
30–100% increased risk by about 52%
More than 100% increased risk by about 128%
That’s why I called it the “new” 10% rule.
Maybe we shouldn’t obsess over whether our weekly mileage increased by 10% (the premise of the “old” 10% rule). Maybe we should pay much closer attention to whether our longest individual run suddenly jumped by more than 10%. If you accept that framework, doubles start to make a lot of sense.
Instead of stretching one run beyond what you’re adapted to, you accumulate more volume by splitting it into two manageable sessions separated by several hours of recovery.
I also think there’s a quality advantage here.
A 5-mile run generally feels better than miles 16 through 20 of a single long run. Your mechanics stay cleaner, fatigue is lower, not to mention that the second run often feels surprisingly good after a full day of eating, hydrating, and moving around.
For me, doubles usually happen once or twice a week.
I’ll do my primary run in the morning (maybe 10 to 14 miles) and then head back out in the afternoon for another 5 to 7 easy miles. It lets me accumulate a high-volume day without needing to cram 17 or 20 miles into the morning session.
Now, one important caveat.
The study was observational, so it doesn’t prove that splitting runs causes fewer injuries. It simply found that large jumps in single-session distance predicted injuries much better than jumps in weekly mileage. Still, I think it’s a really useful way to think about training.
So if someone asked me whether recreational runners should ever run twice a day?
I’d still give it a 10 out of 10—not because it’s necessary, but because it’s one of the safest, simplest ways to increase running volume (when that’s your goal).
If you’re curious about the study itself, I covered it in much more detail in my Run Long, Run Healthy article, “How Much Running Is Too Much?”, where I walk through the data and why I think it’s time to rethink the traditional 10% rule.
Thanks for reading. I hope you enjoyed this new “experimental” post. And if you did, let me know. I’ll try to do more of them in the future.
~Brady~
It seems reasonable, but it begs the question as to what is causing the injuries when our training time exceeds +10%. Is it change in total volume or the spiked volume? What is interesting about this split volume approach, is that it mirrors Dr. Keith Baar’s work on tendons. He has observed that tendons benefited more from volume twice a day, and that longer single sessions actually resulted in tendons breaking down resulting in injury.
How do you feel about rucking to add some volume? Particularly for trail runners (who need more leg stability than road runners would typically need). Thanks in advance!