Running Twice Daily for Marathon Training due to Time Constraints

Hello, I am a 51-year-old woman and am running my first marathon in three months' time. I break up my long runs on Sunday (7 in the morning, 5 in the afternoon or whatever my training schedule is) due to time constraints.

How will this affect me on race day? I do not sleep in between runs.

– Lynne, York, PA

Answer by Dom:

Hey there,
First off, apologies for the slight delay in getting back to you – my schedule's been a bit like a marathon itself recently. Now, onto your question about splitting up your long runs and how it might impact your performance come marathon day.

Let's split up the answer as follows:

1. The Importance of the Long Run
2. Adjusting Your Race Day Goals

The Importance of the Long Run

The long run is so, so important when we're talking about marathon training. A marathon is a test of endurance, requiring you to keep your feet moving for 26.2 miles all at once.

When you train your body for such an endurance-demanding event, you've got to replicate, as closely as possible, the conditions of race day. That means including long runs where you're covering several hours straight, just like you'll need to on marathon day.

These long, continuous runs serve a two-fold purpose. First, they help you adjust to being on your feet for hours on end. Second, they train your body to use its energy stores more efficiently – a key skill for the full marathon distance.

When you run, you burn fuel. Your body has different types of fuel: glycogen, an easy fast-burning fuel that you run out of after long enough, and fat, a much harder fuel to access but one you have plenty of. Every time you run long – longer than 90 minutes – your body gets better trained at accessing fat rather than glycogen as the fuel source.

So by breaking your long run into two, you lose the opportunity to run past 90 minutes and train that fat-burning shift.

But there's something else going on too, and it's specific to why marathon day is so brutal: a single continuous effort builds up cumulative fatigue and dehydration/electrolyte stress in a way that two shorter runs simply don't replicate, even if you sleep between them – and you've told me you don't even get that rest. Your legs, your fluid balance, your glycogen stores all degrade progressively hour after hour on race day. Split your long run into a 7-miler and a 5-miler with a break between, and your body resets before that cumulative load ever builds. You never get the chance to practise running on tired legs, in a depleted, dehydrated state – which is exactly the state you'll be in from around mile 18 onwards on race day.

Think of it this way: two separate 5k runs on the same day don't add up to a 10k in terms of what your body experiences. The recovery gap between them – even a short one, even without sleep – lets your legs and your fluid levels partially reset. Marathon day gives you no such reset. So the gist of it: breaking up your long run isn't just "not optimal" – it's missing the specific, cumulative stress marathon day will put on you.

Adjusting Your Race Day Goals

My first piece of advice would be to find the time to do the long run in one go – even carving out one Sunday a month for it would give your body some exposure to that continuous, cumulative demand before race day.

But assuming that's genuinely not possible, we need to start thinking about race day itself and how to adjust.

My suggestion is to consider turning your marathon into a run/walk marathon. Honestly, I think either way it will end up being a run/walk marathon for you.

Option 1 is to start running and see how long you last, then walk the remainder.

Option 2 is the better approach: regularly alternate running and walking – run 7 minutes, walk 3, run 7, walk 3, and so on. It's an approach many beginner runners adopt, and it could help you handle the marathon's significant demands.

One more tip: try finding time mid-week for runs longer than 90 minutes. A mid-week, somewhat-long run is an important part of a successful marathon build-up. In lieu of a single weekend long run, it may help get you that bit more prepared and make the whole challenge a little less daunting.

It's also worth practising your hydration and fuelling strategy on whatever long runs you do manage in one go. If your body's never had to manage electrolyte and fluid loss over two-plus continuous hours, race day will be the first time it's tested – and that's not somewhere you want a surprise. Sip regularly, take on a sports drink or gel every 45 minutes or so on your longer efforts, and treat those sessions as a rehearsal for exactly what marathon day will demand.

Wishing you all the best in your marathon endeavours.

Kind regards,
Dom

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