Doubles: The How, Why and When of Running Twice a Day
It’s Sunday morning. You’re about to head out the door to run for two hours when you receive an email from work. You could easily split your run into two 1-hour sessions so that you finish the report, but then you ask yourself, “Can I cut one run into two? Will my body get the same benefits?” Great question.
Running doubles may seem pretty hardcore. If you spend a lot of time at a running club, or have eavesdropped on conversations between elite runners, you have probably heard the concept of doubles: running twice per day. In my case that’s how it happened: I was running with the local club and a 2:11 marathoner (the best in my country) happened to visit our club and run with us that day. That’s when I first heard the word ‘doubles’.
Who would train twice a day? Well, doubles are a training staple for elites – I really can’t think of an Olympic runner who doesn’t do them. Doubles work perfectly for the veterans, so it’s no wonder many of us, the “regular” runners, are considering the benefits of running twice per day.
When to run twice a day
According to conventional wisdom, a longer single run should be more beneficial than two runs in one day. However, there are circumstances in which two runs in a day are better than one. When you are trying to build endurance, longer single runs are best. However, the need for these runs reduces once you have reached your goal, for two big reasons.
First, it’s easier to maintain endurance than to build it; as long as you maintain the weekly mileage, you will not lose endurance. Second, after you complete the base phase, your focus should shift to harder workouts, and more importantly, recovering from them.
Adding a second run in a day can be used to improve recovery and even to enhance adaptation.
If you run less than 35 to 40 miles per week, you are better off running just once per day. Doing a 6-mile run all at once is far better than splitting it in two 3-mile runs. When you perform long single runs you build endurance and become a better runner.
Once the weekly mileage hits a level where your daily runs are averaging more than one hour and a half and your weekend long run reaches two hours or more, it’s actually better to do doubles at least a few times a week rather than extend the length of all of your runs. While it’s true that running doubles takes more time, it’s more difficult to recover between runs, and this will help your body adapt and you’ll become a better runner overall.
When to add doubles
|Race distance training for||Weekly mileage exceeds|
|5 km or less||40|
|9 km to 14 km||50|
|16 km to 26 km||60|
|32 km to 42.195 km||70|
I ran twice per day when I was training for a trail ultra marathon earlier this year. The secret to recovering fast is to consume at least 300 calories of protein and carbohydrates immediately after the first run. In addition to this, the two runs should be spread at least 5 hours apart and you should get at least 7 hours of sleep every day.
One great tip I have for running twice a day is to make sure you do some dynamic stretching before your second run.
When not to run doubles
The day of your long run is the only time you don’t want to run twice in a day. That long single run should be completed all at once, because there are specific metabolic and endurance aspects that can only be obtained by continuous running. Long training sessions are a defining aspect of endurance training. All runners know they need to be done, but many often don’t even consider why.
Well, we perform long runs to deplete muscle glycogen, the stored form of carbohydrates. The adaptations that occur include: increased glycogen storage in your muscles, improved fuel utilization, increased capillaries around muscle fibers, a greater reliance on fat by the muscles, increased mental confidence, increased myoglobin within muscle fibers, and more slow twitch muscle fibers.
Why run doubles?
Adaptation and recovery are not the only benefits of running doubles. When doing single runs you don’t always get a sudden increase in fitness. Instead, when doing doubles each workout triggers the brain to signal specific genes to make functional and metabolic changes. It actually takes multiple runs to translate that signal into a functional change. We all know that increasing your fitness requires a number of stimuli to get the training adaptations you work hard for. You need weeks, or months. Doing doubles will get you to your goals faster.
How does doubling play a role in this?
Well, the two runs are definitely shorter, but they provide an overall aerobic training stimulus two times a day instead of once. This means that the genes that cause those changes I mentioned above, like increased glycogen storage in your muscles, improved fuel utilization, or increased capillaries around muscle fibers, are activated for more time than if you did in one single run. Therefore, the pressure on adaptation is more sustained.
Second, running doubles means dealing with some sort of pre-fatigued state. Your body will access muscle fibers that normally do not get trained, or will just push more into the depths of glycogen stores than in one single run.
The result is a slightly different adaptation process. The aerobic enzymes and the muscle’s oxidative metabolism can be potentially greater when performing doubles.
How to incorporate doubles into your running schedule
If you plan to add doubles to your running schedule, your primary goal will be to increase recovery. There’s no such thing as ‘the most beneficial days’. Start running twice per day on your easy days first. When you’re comfortable with this, add them to your steady or medium long runs and finally your speed workouts. The order in which you should add doubles to your schedule should look like this:
- Easy days
- Steady runs or medium long runs
- Recovery runs
Doing an easy run before your workout will help you loosen up a bit and prime the body for a better effort – provided you don’t get too tired. Doing a second run after a hard workout will help flush nutrients, oxygen, and blood to and from the tired muscles.
All in all, like any other aspect of running, doubles should be introduced gradually. You should start by adding only one double per week, and then another, as you gradually increase the weekly mileage.
Don’t go for a second run if it’s less than 25 minutes. It is hardly worth the extra effort and time both physiologically and in your busy life to shower and change.
Definitely do not add a second run immediately after your weekend long run. It will only interfere with your recovery process and you want to be fresh for your upcoming short, fast runs.
All things considered, running twice per day is really a gradual adaptation process, so do not be discouraged after performing your first double run.