double day training

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

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By Jason Koop,
Head Coach of CTS Ultrarunning

Last week I wrote about why an initial leg up on volume might be the best strategy for you in the near term if you have races this summer. Since that article came out, I received a fair number of questions relating to double day training as a strategy to leg up in volume. Double day training (or running twice in a day) can be a great way to add some additional mileage to your week. However, there are times when double days can be useful, times when they are not as useful, and times they should be avoided.

Who should use double days?

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

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  1. Runners who rarely, if ever, get injured
  2. Runners whose schedules don’t allow for > 2 hour runs during weekdays
  3. Runners who have > 4 years of training experience that 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 of adding in volume as a means of furthering the adaptive process for busy and time crunched athletes. 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. So, 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.

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Keep intensity intact

If you do decide to do some double days, take care that the intensity you have planned remains intact by allowing for proper recovery before any hard workouts. In order to do this, I advise athletes plan their double days for the same day as their interval workout day and perform the intervals in the morning, and second run in the evening. In 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 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 for 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.

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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 > 25% more volume when the month is all said and done. This is in addition to all of the rules mentioned earlier in this article. After sliding the markers on the good old abacus, few runners end up meeting this criterion. 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.


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