The Marathon Training Hack For Long Runs Could Save You From Injury

Long runs are the backbone of marathon training, but let’s be honest they can also eat up entire weekends and leave you wiped out.

If you’ve struggled with injury in the past or simply can’t carve out four solid hours for a long run, there’s another option: bunched long runs.

Instead of randomly splitting up mileage, bunching gives structure and purpose.

The idea is simple: run a chunk of miles one evening, then head out for another the next morning ideally within 12 to 15 hours.

For example, you might cover 6 miles on Saturday night and then head out for ten more Sunday morning.

This approach mimics the training effect of one continuous long run while easing the stress on your body and fitting better into a busy schedule.

Why Bunched Long Runs Work

Lower Injury Risk

The concept actually comes from ultrarunners, who often keep their longest training runs to about a third of their race distance.

When you’re running for hours on end, form inevitably starts to break down stride length shortens, cadence slows, and every landing creates more stress on your joints and muscles.

Similar Physiological Adaptations

Spacing runs 12 to 15 hours apart means your body doesn’t have time to fully replenish glycogen before the second session.

Since it takes roughly 20 to 24 hours to restock energy stores, this setup creates nearly the same training stress as one continuous effort.

You still get the endurance-boosting benefits without the full wear-and-tear of a single, marathon-length run.

Builds Fatigue Resistance

The second run in a bunch forces you to train on heavy legs, simulating the fatigue you’ll feel in the late stages of a marathon.

It can also help you transition to bigger mileage.

Breaking down that intimidating first 18-miler into two manageable parts can make it feel less overwhelming and boost confidence for tackling the distance continuously later on.

More Flexibility for Busy Schedules

Sometimes life just won’t allow for a solid block of long-run time. If you’re a parent without childcare for four hours, but you can manage two separate two-hour windows, bunching makes those miles possible.

Instead of skipping the run altogether, you can still log the distance.

How to Incorporate Bunched Long Runs

I'ts better limiting bunched long runs to no more than four in a marathon build-up often just one or two is enough.

For instance, you might replace an 18-mile continuous run with an eight-miler Saturday evening and ten the following morning. Or, when aiming for 20 miles, you could split it into two 10-milers.

Spread them out every three to four weeks so you’re still hitting plenty of uninterrupted long runs in between.

This method works for all types of runners, but it’s especially valuable for those prone to injury or tackling long runs that take three or four hours to finish.

3 Tips for Making Bunched Long Runs Work

1. Use Them Occasionally

Bunched runs are not a wholesale replacement for long runs. You still need a few continuous 18–22 milers to be fully prepared for marathon day.

Think of bunching as a strategic swap one of your two scheduled 18s, for example, or the middle long run in a series of 18, 20, and 22.

2. Plan for Rest Afterward

Because you’re compressing mileage into a short window, soreness will still set in afterward.

Take a rest day following your second run to allow recovery. Many runners prefer to do a Saturday evening/Sunday morning split, followed by a rest day Monday.

If it works better, you can also double within the same day (like a 6 a.m. run followed by 6 p.m.), as long as you keep downtime in between.

3. Keep the Pace Easy

Don’t treat these runs as tempo sessions.

Both runs should stay at your easy long-run pace. To avoid going out too fast, Rosetti recommends focusing on cadence and step count, keeping things steady and controlled.

This helps ensure you can maintain the right effort in both sessions.

Bottom line‍

Bunched long runs aren’t a replacement for all your long training runs, but they’re a smart tool to balance training stress, reduce injury risk, and keep your marathon build on track even when life (or your body) demands flexibility.