Is it OK to run twice in one day?

Double running isn’t just a training strategy for the elites.


Running twice in a day can bring some great benefits, but it’s something runners often avoid for fear of injury. When incorporated carefully into a training plan, double running can help to build your muscle strength, increase your endurance, improve your running efficiency and – crucially – save time. And the experts agree.

‘Of course, all runners get many of these benefits from any type of running, but doubles can increase and accelerate these,’ says running coach Paul Griffiths.

‘There’s misconception that doubles are something only elite runners do,’ continues Steve Magness, an exercise physiologist and cross country coach at the University of Houston. ‘But a lot of runners can benefit from them.’

Doubling up and running in a depleted state can boost fat-burning, train the body to use glycogen more efficiently and stimulate the production of mitochondria (the structures within cells that produce energy) to delay fatigue. ‘By shortening the time between runs, you are challenging your body to recover faster,’ says exercise physiologist Greg McMillan.

When two runs beat one

During a period of base training, when you’re trying to build general endurance, longer single runs provide the stimulus you’re looking for. But, once you’ve built your general endurance, the need for longer single runs every day shifts for two reasons. First, it’s easier to maintain endurance than to build it – therefore, so long as you stick to a regular long run and your overall mileage hasn’t dropped considerably, you won’t lose general endurance.

Secondly, after your base phase, the emphasis of your training shifts to harder workouts – and, more importantly, your ability to recover from them. ‘It might seem counterintuitive at first, but adding a second run can be used to enhance recovery and even to increase adaptation,’ says Magness.

When and how to double up

‘Cumulative mileage matters – no matter how you do it,’ says Brad Hudson, author of Run Faster from the 5K to the Marathon. And a good way to boost your total mileage is by doubling up once a week – while still keeping that crucial rest day.

Around four to 10 hours after a key workout – such as an interval session or a tempo run – go for an easy run that lasts between 20 and 45 minutes, and don’t fret about pace. This will boost your mileage and also assist your recovery from the first workout by increasing blood flow to the muscles and flushing out lactic acid and other metabolic waste products. The (somewhat surprising) result? Fresher legs for your next run.

Logging two 40-minute runs rather than one 80-minute session delivers a double boost of human growth hormone, production of which peaks about 40 minutes into a run. This hormone helps to build and repair muscle. However, there’s still no substitute for the weekly long run when it comes to building your overall endurance, muscle strength and mental readiness, particularly if you have a half marathon or marathon in sight. With that in mind, Magness advises that you should maintain your long run and key workouts and only split mid-length runs.

It’s also important to build up doubles gradually, says Griffiths. ‘If runners want to do double running days, then I build it in carefully and sensibly, starting with one double day a week for month one of training before bringing in more, as needed, every couple of weeks. This approach enables the athlete to build up tolerance to going out twice a day and therefore reduces the risk of fatigue, burnout or injury.’

How splitting one long run into two can boost recovery

A common yet surprising result of doing two runs in one day is that you often feel more recovered the following day. The most obvious reason is that, by running two shorter distances, you don’t beat up your body as much as you would on a longer single run. On these shorter runs you have plenty of fuel stores and rely primarily on your heavily fatigue-resistant slow-twitch muscle fibres. The result is no lingering fatigue or damage.

‘Instead, you get an increase in blood flow twice to help with recovery and, perhaps more importantly, an increase in hormones (such as growth hormone) that help with recovery,’ explains Magness. ‘Getting a good hormonal spike to aid recovery twice during a day does wonders for getting you recovered for the next day’s workout.’

How doing two shorter runs can improve your fitness

‘The benefits of doubles go beyond just recovery,’ says Magness. ‘One workout by itself doesn’t translate to a sudden increase in fitness. Instead, each run triggers the body to signal certain genes to make functional adaptations. It takes multiple runs or workouts to translate that signal into some sort of functional change.’ In other words, you need an accumulation of stimuli to achieve the training adaptations you work so hard for.

Doubling plays a role in this in two ways. A general aerobic training stimulus twice a day instead of once means that the genes that cause desirable changes, such as increased mitochondria or an increase in oxygen-carrying capacity, are activated for a greater total time than if you did just one run. So, you have a much more sustained pressure on adaptation.

‘Also, by running doubles, especially after a hard workout, you’re training in a pre-fatigued state,’ add Magness. ‘Doing so allows you to access different muscle fibres that you might not normally train, or to push further into the depths of glycogen depletion than you would normally.’

As a result, you get a slightly different stimulus for adaptation. Research looking into training twice a day versus once a day for the same total weekly volume has shown that the increases in aerobic enzymes (proteins that facilitate energy production) can be potentially greater when doing two bouts of exercise relatively close together.

Building double run days into your schedule

‘When the goal of doubling is to enhance recovery, split your mileage for the day as evenly as possible,’ says Magness. ‘For example, if you had planned to do eight-miler, do two runs of four miles each. By splitting it evenly, you minimise fatigue but get an even boost of all the aforementioned good stuff twice in one day.

‘For my athletes, I most often schedule recovery doubles like this the day after a hard day,’ continues Magness. ‘A typical example would be to do a hard workout on a Tuesday, then follow that up with a Wednesday that includes two short runs, a normal-length single run on Thursday and another hard workout on Friday. This type of schedule allows for a nice mix of split doubles to enhance recovery while still including some single runs to maintain general aerobic ability.’

If your goal with doubling is to get a little more bang for your buck when it comes to training adaptation, schedule a double for when you know you’ll be a little fatigued. So, an example is to place a second, shorter run of three to six miles the afternoon after a hard morning workout. It’s unlikely you’ll be fully recovered from the morning workout, so you’ll be doing the second run in a slightly pre-fatigued state. Not only will you squeeze out more adaptation, but you’ll also enhance your recovery.

Finally, doubles can be used to prime the pump for workouts or races. In this case, you would want to do the double during the morning before an afternoon workout. The short morning run would prime the body by flushing out the system and manipulating the muscle tension so that you’re in a better position, physically, to run the hard workout in the afternoon. When using this method, keep the run short – say, between two and four miles. You can also do this a few hours before an afternoon or evening race, perhaps with some light strides at the end to top it off.

Can double days help runners to get PBs?

Seasoned runners with a solid aerobic base and an ambitious time goal can increase their strength and speed with a regime of two daily targeted workouts. ‘This approach is for people who have pushed their training as far as they can and are looking for an extra boost,’ says Magness.

To your quality days, add a second, shorter intense workout (which is half to three-quarters of the length of your first run) tailored to your race goal. So, if you’re trying to improve your speed over the half marathon or marathon, for instance, follow a morning tempo run with an afternoon endurance-building session of 3 x 1-mile repeats at slightly faster than tempo pace.

If you’re targeting a PB in a 5K or 10K, do your usual speed work in the morning and add shorter, faster hill repeats or intervals in the evening, says Hudson. For example, do 4 x 2km repeats at 10K pace with a three-minute recovery between each rep, followed by 4 x 400m at 3km pace with one-minute recovery.

‘With most workouts, you come in pretty fresh,’ says Magness. ‘With these blocks, you’re coming in tired. You have to use muscle fibres you don’t typically use, so your body has
to develop a different strategy to dig a little deeper.’

Such efforts make recovery even more critical than it normally is. On rest days, really rest – so take the day off completely. ‘It can actually make people smarter about their training to know these double days are coming up,’ says Hudson.

The risks of doubling up

The main risks of doubles are burnout and fatigue, both of which can impact the rest of your training and prevent progress and consistency.

The other thing to remember is that doubles can’t replace those longer runs. ‘When an athlete trains on a long run of two hours, the training really benefits their aerobic and anaerobic base,’ says Griffiths. ‘So while the odd double day – which, in this case, splits the long run into two one-hour runs – isn’t a big issue, it isn’t something you would want to do regularly, as you would lose the benefit of the long run.’

Doubles can help runners to improve, but they should be considered carefully and weighed up against the risks. ‘Like all things in running training, you can test it out and look at the data,’ adds Griffiths. ‘See how you feel and see if they can help you to achieve the goals you have.’

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