Do’s and Don’ts of Double Day Training for Ultrarunners

By Jason Koop,
Head Coach of CTS Ultrarunning
Updated 2024

If you are an ultrarunner and you’re considering two-a-days or double days for your training, you’re going to want to read this first. Training twice in one day can have its place in ultramarathon training, but the practice should be used sparingly and in the appropriate context. Here’s how I use, or forgo, double days for ultrarunners

When I first started as a professional coach, I blindly regurgitated some of the patterns and protocols I had used as a runner in college. One was the infamous double day. Every Monday through Friday, our cross-country team at Texas A&M would religiously do our hard workouts in the morning, followed by an easy 30-60 minutes in the afternoon. I didn’t give the second workout much thought. After all, I was in my early 20s, a relatively good athlete, and had the requisite physiology to be able to tolerate and respond readily to stress.

As I became a professional coach, however, I had the great fortune of having someone far more experienced looking over my shoulder and scrutinizing every letter I wrote on athletes’ training programs. One of those coaches was Jim Lehman and the advice he gave me during those early years, particularly around how to effectively use double days, stuck with me. Coach Lehman forced me to think about how much those extra minutes matter in the context of the whole training program, how to effectively leverage double days for a specific purpose, and how to avoid assigning workouts for no reason.

Who should use double days?

Double days can be effective for ultrarunners who meet the following criteria:

• Runners who rarely, if ever, get injured
• Runners whose schedules don’t allow for weekday runs longer than 2 hours
• Runners with more than 4 years of training experience who have hit a performance plateau

So, if you fit into any one of these categories, listen up. Adding a couple of two-a-days might be right for you.

The right type of double day training

At their core, double days are a way for busy and time-crunched athletes to add volume to further the adaptive process. The easiest way to do this is to simply add a second run of 60-90 minutes to the day (either in the morning if you are normally an evening runner, or vice versa). Over time, these runs add up to produce higher amounts of volume and theoretically bigger adaptations. The process is simple: add 1-2 runs of 60-90 minutes 1-2 days per week. Adding a second run shorter than this within the same day is generally not worth the effort, as the additional volume–as a percentage increase above your original volume–is not enough to elicit further improvements.

Always add, never subtract

When planning your double days, you should always be adding to the single run volume you would normally do, ever subtracting from it. For example, if you normally run 90 minutes per day, splitting that run into two one-hour runs is not worth the time and effort, even though the double day would result in a higher net volume. This is because the physiological strain, and therefore adaptation, resulting from a run is a product of both duration and intensity. And the longer the duration of any one workout, the higher the strain. You intuitively know this because the last 30 minutes of a 2-hour run is harder than the first 30 minutes, even if they are run at exactly the same pace.

Keep intensity intact

If you do decide to do some double days, take care to preserve the intensity that was already planned by allowing for proper recovery before any hard workouts. To do this, I advise athletes plan their double days for an interval workout day and perform the intervals in the morning, followed by the second run in the evening. This way, the following day can remain a RecoveryRun day and allow for more complete recovery until the next hard run.

Be consistent

Just like an individual very long run will not make or break your season, one double run day is not going to turn you from a sloth to a superhero. Remember, endurance adaptations are chronic. They take weeks and months, not days or hours, to manifest into some reasonable improvement. So, if you are planning to engage in double days, do it for the long haul. Plan on dedicating at least 8 consecutive weeks to the higher volume load to reap any meaningful rewards. If you anticipate only being able to do doubles sporadically or on an inconsistent basis, it’s better to forgo them and focus on your single day runs.

What about cross training double days?

Some athletes and coaches ascribe to using a cross training modality (normally cycling) as the second workout of the day as a means of increasing overall aerobic volume. The schedule normally looks like this:

This scenario also comes up with athletes are using cycling to commute to/from work. While not entirely problematic, the extra cycling volume is unlikely to add much in terms of improvement. A couple of hours of low intensity cross training, in the context of a training schedule that is ~10-15 hours per week, is simply not enough stress to be meaningful. If you like getting on the bike or elliptical a couple of times per week, then great! Just don’t let it interfere with your harder or more important workouts. But, if you expect magical improvements from this additional aerobic exercise, don’t hold your breath.

Why double day training is not for everyone

I only end up prescribing double days for a very small percentage of the athletes I work with. This is because, minute-for-minute, single run volume is more effective than double run volume. In fact, my internal rule of thumb is that if I am going to apply double runs to an athlete, it should result in greater than 25% more volume when the month is all said and done. This is in addition to all the rules mentioned earlier in this article. After sliding the markers on the good old abacus, the math only works out for a few runners. However, if you feel you can gain 25% more volume, will not get injured, and can maintain your single run volume uninterrupted, doubles might be an effective tool to incorporate into your training plan.