Can I Split My Long Runs?

two men on an early morning run
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"I'm training for a marathon and sometimes I don't always have time to do my long run all at once. Is it OK if I split up my long run by running some miles in the morning and the rest at night?"

Finding time for the long runs is a common issue for marathoners-in-training. I wouldn't recommend doing it every week, but splitting up your long run can be an option during a busy week. It's also a good strategy for dealing with high heat and humidity in the summer because you can take advantage of cooler temperatures in the morning and evening.

Some runners who are injury-prone or those who would need 3+ hours to complete a 20 mile run also choose to split their long runs as an injury prevention strategy.

By running some of your mileage in the morning and the rest later on during the day, your body is getting most of the same physical endurance training benefits of a continuous long run since you're not completely recovering in between runs. Since you're not sleeping in between runs, your body doesn't have enough time to make significant recovery. Your legs are fatigued already and your energy stores are somewhat depleted, so you do get some cumulative effect.

However, the benefits are not as great as when you do one continuous long run. One goal of long slow distance is to train your muscles to spend hours running, just as you'll do on race day. You need to learn to run through fatigue and practice pacing and fueling. And, of course, it's definitely easier mentally to run 10 miles in the morning and 8 miles at night, rather than 18 miles all at once -- which is why you don't want to do it every week.

Ideally, you want to run your long run continuously, since that's what you'll be doing in your marathon. But splitting your run is a great way to squeeze a long run into a busy week and it definitely beats the alternative of skipping your long run altogether.

Also see: Frequently-Asked Marathon Training Questions
6 Tips for Busy Runners

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