Marathon Pacing: How to Run the Second Half Faster

Marathon pacing is the difference between a great race and a painful one. Most runners know this in theory. Very few execute it well on race day.

The common pattern goes like this: the crowd energy carries you through the first 5km faster than planned. The legs feel good. The pace feels easy. You decide to bank some time. By kilometre 30, you're in serious trouble.

This article is about why that happens, and a more reliable approach to pacing, one that leaves you feeling stronger in the final kilometres than you did at the start.

Why runners go out too fast

Starting a marathon at the right pace is genuinely hard. Race day adrenaline, a big crowd, the feeling of fresh legs, and months of taper all conspire to make the early kilometres feel deceptively easy.

The problem is physiological. When you go out too fast early, you deplete glycogen at a rate your body cannot sustain. The wall, that sudden loss of pace and energy most runners experience around kilometre 32 to 35, is usually the direct result of poor early pacing, not a lack of fitness.

Research consistently shows that positive splits (running the first half faster than the second) lead to slower overall finishing times. Almost every marathon world record, including the recent sub-2-hour breakthroughs discussed in our piece on what the London 2026 marathon means for everyday runners, was run with a negative or even split.

What a negative split actually means

A negative split means running the second half of the race faster than the first. The difference does not need to be dramatic. Even 30 to 60 seconds across the full second half is enough to make a meaningful difference to your finish time and how you feel crossing the line.

The reason negative splits work comes down to energy conservation. When you run the first half conservatively, you burn stored glycogen at a sustainable rate. You arrive at the halfway mark with more fuel in the tank, which means you have something left when other runners are fading.

There is also a psychological benefit that is easy to underestimate. Passing people in the second half of a race is energising. Being passed is demoralising. A well-executed negative split almost guarantees you will be the one doing the passing from kilometre 30 onwards.

How to pace for a negative split: the 10-10-10 method

A simple framework that works well for most recreational runners is the 10-10-10 approach, which divides the marathon into three distinct phases based on effort and pace.

Phase 1 (kilometres 1 to 16): Run 15 to 20 seconds per kilometre slower than your goal pace. This will feel uncomfortably easy at the start. That is exactly right. If someone asked you to stop and have a conversation in the first 10km, you should be able to do it without much effort.

Phase 2 (kilometres 17 to 32): Settle into your goal race pace. Your legs should feel warmed up and ready to hold the effort. This is where the race actually starts for most people.

Phase 3 (kilometres 33 to 42.2): Hold goal pace or push slightly if you genuinely have the energy. This is when you start picking off runners who went out too hard in Phase 1.

The biggest mistake runners make is starting Phase 2 too early. The first 16 kilometres should feel like a training run, not a race. Trust the plan.

Training for a negative split

You cannot just decide on race day to run a negative split. You need to practice it in training so the execution feels natural rather than forced.

The most effective method is the back-end long run. On your long run day, start at a comfortable conversational pace and spend the final 20 to 30% of the run at your goal marathon pace or slightly faster. This teaches your legs to work harder when fatigued, which is exactly what the final 10km of a marathon demands.

Zone 2 training fits naturally into a negative-split approach. Most of your easy running should be genuinely easy, aerobic, and conversational. That low-intensity base builds the aerobic engine that sustains your pace through the second half when other runners are glycogen-depleted and falling apart.

Strength training also matters more than most runners expect. A stronger posterior chain, specifically glutes and hamstrings, means less form breakdown in the final kilometres when fatigue sets in. Running economy holds up much better in tired legs when there is genuine strength underneath the aerobic engine.

Tempo runs and threshold work once per week help you develop pace awareness. After enough sessions, you stop relying solely on your watch and start recognising what goal pace feels like by effort alone. That internal calibration is what saves you when race day nerves tempt you to push earlier than planned.

If you are planning your training block around a specific race, the Australian Running Events 2026 guide covers the full race calendar so you can time your peak preparation correctly.

Race day execution

Write your phase splits on your wrist or race bib before the start. Having them visible removes any guesswork in the first hour when excitement is highest and the temptation to push is strongest.

Start fuelling at around the 5km mark, not when you feel like you need it. By the time you feel low on energy mid-race, you are already behind. Consistent fuelling every 20 to 25 minutes keeps glycogen levels steady throughout and avoids the crash that catches so many runners in the final 10km.

If you are running with a GPS watch, set a pace alert for the upper limit of Phase 1. If your watch beeps because you are going too fast in the first 10km, listen to it. That alert is doing its job.

Aim to reach the halfway point feeling like you could run that distance again. If you already feel like you have worked hard for it, something went wrong in the first half and you will need to adjust your expectations for the second.

Gear that helps on race day

A few items make a genuine difference when you are out there for three to five hours:

GPS watch. Essential for pacing. Real-time pace feedback is the most reliable way to hold Phase 1 discipline when your legs feel fresh and the crowd is pulling you forward.

Fuel and hydration. Gels, chews, or whatever you have practised in your long runs. Race day is not the time to experiment with anything new. If it worked in training, stick with it.

Running sunglasses. A marathon means hours on the road, often through changing light as the sun climbs. In Australia, UV exposure at morning race starts is significant even in the cooler months. Photochromic lenses adapt automatically from darker to near-clear as you move between open exposed sections and shaded stretches, which removes one less thing to think about mid-race. The Infinity lens adds polarisation and anti-fog to that system, useful in the early kilometres before you have properly warmed up. Fit matters too: sunglasses that bounce or shift are a real annoyance over 42km. If you are figuring out which lens suits your race conditions, our lens guide is a good starting point.

Race kit. Test everything in training. A chafe point that seems minor on a 10km run becomes significant by kilometre 35 of a marathon.

What to expect

A negative split takes practice to execute well. Most runners will not nail it on their first attempt because holding back when you feel good is genuinely counterintuitive.

The goal is gradual improvement across race cycles. If your first marathon was a heavy positive split, aim for even splits next time. Once you can run even splits consistently, start working toward a small negative margin. Small improvements compound significantly across multiple races.

Running consistently between race cycles matters more than any single training session. The aerobic base you build over months is what ultimately determines how your legs perform in the final 10km when pacing decisions matter most.

If you are building towards your first major event, the principles in our guide to preparing for your first trail race cover a lot of the same preparation logic that applies to road marathons: consistent training, conservative early pacing, and trusting the process rather than trying to perform on the day.

The takeaway

Pacing is a skill, not a guess. Run the first half conservatively, stay patient through the middle, and let the second half be where your race actually happens. The runners who execute that plan well almost always finish stronger than they expected.

If you are still sorting out what gear to bring to the start line, our Find Your Pair guide walks through which Re. sunglasses work best for different race conditions and light environments.

Go find your pace.