Doubles: The When, Why, and How to Run Twice a Day

If you’ve spent enough time at your running club’s favorite watering hole, or happened to ease drop on a conversation between veteran runners, you’ve probably heard the concept of running twice per day. Runners often refer to this practice as “running doubles”.

Doubles are a training staple for elite athletes – I can’t think of an Olympic athlete 1500 meters and above who doesn’t do them. Since they work so well for the elites, it’s no wonder why many “regular” runners question if they could benefit from running twice per day.

It’s a fair question and I think the answer lies in looking at the advantages and disadvantages of running twice per day and then analyzing where you fit in on the spectrum given your current training and goals. Here’s what the evidence suggests:

Advantages of double runs

Despite what the latest fad a catchy magazine headline might try sell you suggests, to run faster you have to run more. Running well at distances over 5k relies primarily on your aerobic endurance and development. Therefore, anything that a runner can do to boost their mileage will contribute to their overall development and progression.

Increased training benefits

The primary benefit of adding double runs to your weekly routine is that running twice per day puts your body in a glycogen depleted state, which enhances training adaptations, especially if you’re training for a marathon. Scientifically speaking, studies have shown that glycogen content, fat oxidation, and enzyme activity increase when training twice per day. In moderation, this means you’ll get fitter faster.

More efficient recovery

Running one 8 miler is definitely harder on the body than running two 4 milers. You don’t have to be a rocket scientist to know that training will be easier when you have the chance to rest and refuel between runs. Furthermore, since the purpose of an easy run is to facilitate recovery, running twice per day increases the frequency at which you speed blood, oxygen and nutrients to the muscles.

Easier to manage long training days

For runners who are already waking up before dawn to get in their miles, adding more mileage to their morning routine might not be feasible. However, by incorporating doubles and turning their 8 or 10 miler into two runs, one in the morning and one in the evening, they can safely boost their overall mileage without being late for the morning commute.

Disadvantages of double runs

Interestingly, the same advantages described above can actually be disadvantages if you’re not an experienced runner with a significant aerobic base. Simply speaking, once you’ve been training at a high level for 3-5 years, the aerobic advantages of an easy run start to follow the path of diminishing returns. You still derive benefit from an easy 8-10 miler, but not as much as a beginner runner whose aerobic endurance isn’t anywhere near its limit.

60-90 minutes is optimal for building aerobic endurance

If you haven’t been running higher mileage (50-60 mpw) consistently for at least 3-5 years, the bulk of your improvements are still going to come from improving your aerobic endurance. Therefore, maximizing the number of runs you spend in the 60-90 minute range (widely considered to be the critical time threshold for enhancing aerobic fitness at the cellular level) is the most effective training method. Doubling will lend itself to more runs in the 30-45 minute range, which are still beneficial, but don’t increase endurance as much as a 60-70 minute run will.

Recovery can be hampered

While easy runs do promote recovery by enhancing blood flow, they can also make you tired – as you’ve undoubtedly experienced before. If your fitness isn’t yet at a level where a 30-40 minute run barely leaves you breaking a sweat, the increased stress can actually hamper recovery instead of promoting it.

Feels like you’re training all day

Running doubles requires significant dedication. It’s not easy to lace up the shoes twice per day, even if it’s only a few times per week. While I don’t think this would actually stop any runner from trying them, it can be a burden on your sleep needs, eating habits, and general attitude about running.

When you should incorporate doubles

Now that you’ve seen the advantages and disadvantages to running doubles, it’s easier to appreciate what type of runner would benefit from incorporating them into their training routine.

Generally, doubles will benefit more experienced runners who have maximized aerobic development but still need to boost mileage without having their easy days be over 80-90 minutes or who are looking to recover more efficiently in preparation for harder workouts.

Here’s a brief breakdown of what type of mileage numbers you should be at before adding doubles to your training regimen:

How to incorporate doubles

When first adding doubles to your training, the primary goal should be to promote recovery. However, coaches differ on which days running a double will be the most beneficial. Typically, we recommend adding double runs to your easy days first. After you’re comfortable adding doubles to your easy days, you can add them to your workout days, starting with your steady or medium long runs and finally your speed days. For simplicities sake, here’s the order in which you should add doubles to your routine.

1. Easy days
2. Medium long runs or steady state efforts
3.Tempo runs or cruise intervals
4. Speed workouts

It doesn’t matter much if your second run comes before or after the main run for the day. Running before your workout will help you loosen up and prime the body for a better effort – provided you don’t get tired. Running your double run after a hard workout will help flush blood, nutrients and oxygen to and from your tired muscles.

Some notes

Running twice per day means you’re stimulating your metabolism more often and increasing the amount of calories you burn. Make sure you eat enough to properly recover and replenish the essential nutrients you need to keep making gains.

Give yourself enough time in between runs. Double runs are not as effective if you run them 2 hours apart. Try to keep the time between runs to a minimum of 5 hours. I’ve found 7-8 hours to be optimal.

As a RunnersConnect member, we do all the thinking for you when it comes time to decide if it’s best to add doubles to your training schedule. However, I think this article will help answer any questions you may have about the potential benefits and disadvantages, as well as shed light on when your coach or training plan might start adding them to your routine. As always, feel free to let us know if you have any questions or your own take on doubles – we’re here to help.

A version of this post originally appeared at competitor.com