[Research Rundown] Double Run Training: When Running Twice a Day Makes Sense (and When It Doesn’t)

Maybe you’ve seen elites doing it. Maybe your friend won’t shut up about how “life-changing” it’s been. Or maybe you’re just thinking, “If I run more, I’ll get faster, right?” For a lot of runners, the idea of splitting a longer run into two shorter runs - or running twice in one day - sounds intriguing, especially if your schedule is bananas, you recover better from shorter sessions, or fitting in one big chunk of time just isn’t always realistic.

So… are doubles actually a smart strategy for non-elites? A new study looked at exactly that: what happens when you do one longer workout vs. two shorter ones with the same total volume. Let’s break down the results, what they mean for recreational runners, and how to use this info in real life WITHOUT digging yourself into a fatigue hole.

What the Science Found (One vs. Two Sessions)

So here’s what this study looked at: researchers had 14 well-trained endurance athletes do the same threshold workout - six 10-minute intervals at moderate intensity - but on two different days. One day, they did all six intervals in one go (classic big session). On another day, they split the workout in half: 3 x 10 minutes in the morning, and 3 x 10 minutes in the afternoon, with about 6.5 hours of recovery time in between.

Same total work.

When the athletes did the one long session, things got harder as the workout went on (shocking, right?). Heart rate drifted up, lactate levels climbed, and their perceived effort got noticeably higher by the last couple intervals. Basically, they were working harder just to maintain the same pace, something any runner who’s gutted through the end of a long workout knows all too well.

But when they split the session into two parts, their bodies didn’t accumulate fatigue in the same way. Heart rate stayed lower during the second workout compared to the second half of the longer workout, measured lactate was lower, and the second half of the workout actually felt easier than the first. Post-workout recovery? Also easier. Less muscle soreness, lower resting heart rate, and fewer “why did I do that” vibes the next day.

So what does this mean?

The long workout packed a bigger punch - more fatigue, more physiological stress, and likely a bigger signal to the body to adapt. The double split sessions, on the other hand, let them rack up the same total work with a lower immediate cost. It’s kind of like eating a giant burrito all in one go vs. half for breakfast, half for dinner. Same calories. Different digestion experience.

But here’s the catch: that doesn’t mean one is automatically better than the other. It just means they do different things to the body, and understanding those differences can help YOU make the right decisions.

Trade-offs in Real Life: Schedule, Durability, and Recovery

So… should you run once or twice a day? Like with most training decisions, the answer is: it depends. Here’s how to think through the trade-offs in the real world - not in a lab.

Your Schedule Might Be the Boss

Let’s be honest: for a lot of runners, this isn’t a question of “what’s optimal”... it’s “what the heck can I actually make work?” If you’ve got a packed calendar, splitting a 60-minute run into two 30-minute chunks might be the only way training happens that day. I’ve coached plenty of runners - busy parents, shift workers, folks with long commutes - who thrive with doubles because they have to. It’s a logistics move, not a flex.

In those cases, two shorter runs can keep you consistent without having to carve out a huge block of time. Just be prepared for the trade-offs: two warm-ups, two cool-downs, maybe two showers (unless you’re rolling up sweaty to that Zoom meeting - no judgment).

Building "Fatigue Resistance" Matters

That said, there’s a reason long runs haven’t gone out of style. Doing one continuous longer effort builds a kind of mental and physical resilience that you don’t get from stopping halfway and hitting reset. The back half of a long run - when your legs are tired and your form starts to break down - is where a lot of important adaptations are triggered. That’s when your body is learning to stay efficient under fatigue. It’s what builds the kind of durability that helps you finish strong in races.

So if you’re always breaking your longer runs into two parts, you’re missing that specific stress - and the adaptation that comes with it. That doesn’t mean every long run has to be continuous, but if you're training for a half marathon or marathon, those long, unbroken efforts are non-negotiable.

Recovery Is Non-Negotiable

Here’s something that often gets skipped in the “just do doubles!” conversation: splitting a workout only works if you can actually recover between runs. That means eating something, hydrating, sitting down for a bit, maybe even napping if you’re fancy (and can, ya know, take a nap in the middle of the day).

The athletes in the study had structured recovery time between sessions - which is not the same as dashing from a 6 a.m. Workout #1 to a 10-hour workday and then forcing yourself out the door at 8 p.m. for Workout #2.

So if you’re going to run twice, build in the support around it. No support? Then cramming in a second run might just leave you more tired - and more likely to get hurt.

The 4 Basic Types of Double Runs

Not all doubles are the same - and what you’re trying to get out of them matters. Here are the most common types of double run setups and how they actually play out for most recreational runners.

1) Splitting One Workout Into Two Sessions

Got a long or challenging workout on the schedule, but can’t fit it all into one go? You split it - half in the morning, half later in the day. This is the most common and realistic way recreational runners use doubles.

✅ Good for: busy schedules, breaking up long workouts

⚠️ Watch for: overdoing both halves instead of evenly splitting the effort

2) Workout in the Morning + Recovery Run at Night

This is a classic structure for higher-level runners: hard effort early, shakeout or recovery jog later to boost blood flow and help the body recover. In elite training, this is often how “doubles” are used - not for extra fitness, but to aid recovery and add more low=intensity (i.e. "easy") volume to the week.

✅ Good for: adding volume + recovery support when weekly mileage is already high

⚠️ Most recreational runners don’t need this unless you’re running ~6+ days/week

3) Two Easy Runs

Think: 6 miles in the morning, 4 miles in the evening, instead of 10 miles all at once. This is a common approach in high-volume training plans to get mileage in without having to run 90+ minutes on a "regular" weekday.

✅ Good for: experienced runners trying to increase volume without overstressing a single session

⚠️ Not necessary unless you’re already bumping into the time/duration ceiling of your runs

4) Double Threshold Training

This is the high-performance stuff - two workouts at threshold intensity in a single day, usually separated by 5–6 hours. Used by elite athletes (like the Norwegians) to stack up a high volume of threshold work without maxing out in one session. It’s highly structured, carefully monitored, and not something to wing.

✅ Good for: some elite-level athletes with world-class recovery, experience, and blood lactate monitoring available (but there's a reason most elites don't do this: it's A LOT to handle)

⚠️ NOT for most recreational runners. If you’re not already thriving on weekly threshold workouts, this is way too much.

For Most Recreational Runners…

You’re probably not doing double runs to add more training volume to an already maxed-out schedule. You’re probably doing it because:

• Your day is a time-management jigsaw puzzle

• A long run in one go feels like too much right now

• You recover better from shorter sessions

• Life said “Nope” to your original plan

And that’s fine! Most recreational runners who double are doing modified versions of single-session runs - not stacking on extra mileage just for fun. The key is making sure you’re still honoring the intent of the workout and not doubling your stress or skipping recovery.

Making Running Twice a Day Work for You

Here’s the bottom line: double runs aren’t magic, and they’re not required. You don’t get extra credit for running twice in one day. But if done intentionally - and for the right reasons - they can be a useful tool.

If you're an intermediate runner with a solid base, a decent recovery routine, and a life schedule that’s a little chaotic? Splitting a run into two might help you get the work in without torching your energy or sacrificing training quality.

For example:

• Can’t fit in your whole 2-hour long run this weekend? Do 90 minutes in the morning and 30 in the evening.

• Have a threshold workout that usually leaves you completely drained? Split it into two smaller sessions and keep the intensity cleaner in both.

• Want to bump up your mileage but every single run is already stretching your time and energy limits? Maybe one extra short, easy double day helps distribute volume more manageably.

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But remember: doubles are a tool, not a rule. If you're constantly feeling worn out, skipping recovery, or stacking doubles on top of poor sleep, stress, and inconsistent nutrition... it’s going to backfire. Quickly.

Ask yourself:

• Am I using doubles to make my training more manageable? Or am I just doing more for the sake of more?

• Am I recovering between sessions? Or just surviving them?

• Am I honoring the purpose of the run(s)? Or turning everything into “kind of a workout”?

  
  

If a double helps you stay consistent, feel better, and fit your training into real life - awesome. If it makes you tired, cranky, or injured - ditch it. One quality run a day (or even fewer!) is plenty for most runners to make solid progress.

Ready to train smarter (not just harder)?

If you’re wondering how to structure your training, when to push, when to pull back, or whether things like double runs even make sense for you, I’ve got resources to help:

✅ Downloadable Training Plans – for every distance, from 5K to marathon

✅ 1:1 Coaching – personalized guidance, support, and feedback from expert coaches

✅ Group Coaching Programs – structured team training for specific race goals

Wherever you are in your running journey, I'm here to help you run smarter, build confidence, and enjoy every step!

Sources Kjøsen Talsnes R, Torvik PØ, Skovereng K, Sandbakk Ø. Comparison of acute physiological responses between one long and two short sessions of moderate-intensity training in endurance athletes. Front Physiol. 2024;15:1428536. Published 2024 Jul 30. doi:10.3389/fphys.2024.1428536