What are fast finish runs and are they the secret to a new PB when racing returns?

Ashley Mateo
Photo credit: K.C. Alfred - Getty Images

From Runner's World

No champion or world record-setting runner ever earned their accolades by running the second part of a race slower than the first. Negative splits are one of the holy grails of distance running, but it’s easier said than done to pick up the pace the further you get into a race. While a typical training plan calls for speed and endurance workouts, combining the two in a fast finish run can help you train your body to shift into a higher gear when it matters most.

What is a fast finish run?

It’s almost as straightforward as it sounds: You finish a run faster than you started it. But we’re not just talking negative splits here. 'A fast finish run is a formal workout, some kind of structured, faster running at the end of a run,' explains Jason Fitzgerald, a USATF-certified running coach and founder of Strength Running in Denver, CO.

That could mean you run the last few miles of a run at goal race pace (imagine a 30- to 60-minute long run at an easy or aerobic pace, followed by 15 to 25 minutes at 10K to half marathon pace). Or it could be a speed workout within the second half of a long run (for marathon runners: 11 miles at an easy pace and then 3 reps of 3 miles at goal race pace followed by 1 mile at recovery pace). It could also be more of a progression, where you just get a little bit faster every few minutes during the last 2 or 3 miles of a run.

Trying to get to that faster pace after a significant amount of running is supposed to feel hard. 'Usually, the fast miles at the end of the run are faster than marathon pace,' says Amanda Nurse, an elite runner and running coach based in Brookline, MA. 'You should be hitting around 90 percent of your max heart rate.'

What’s the point of fast finish runs?

Fast finish runs are all about preparing your body for the extra effort it takes to perform the further you get into a race. 'After about two hours of running, you start to exhaust your slow twitch muscle fibres,' says Fitzgerald—your main power source during distance running. ‘To pick up the slack, your body starts to recruit fast twitch muscle fibres,' he explains. These are the muscle fibres responsible for short, explosive efforts like sprints.

Even if you don’t pick up speed at all, your tired legs will start utilising more of those fibres. But if you can pick up the pace after your body has started recruiting those fast twitch fibres, you’re putting your body under more stress, which forces more adaptation (a.k.a. improvement). 'Incorporating speedwork into longer runs isn’t going to make you a faster sprinter, but it helps improve your speed in a way that benefits distance running,' says Nurse. 'Learning to run on tired legs without slowing down will make your overall pace faster.'

Fast finish running also teaches your body to burn a higher percentage of fat. 'Run at the time in a long run where you start running low on fuel, then you start increasing the intensity, you’re increasing the energy demands of the workout,' says Fitzgerald. 'Your body gets that energy by burning a little more fat than carbohydrates.' When you’re running mostly on carbs, your body’s glycogen stores bottom out around the two-hour mark (when many people 'hit the wall'); if you can push back that mark by training your body to better tap into fat stores, you’ll be able to maintain your goal pace for longer.

There’s also a huge element of mental training happening during a fast finish run. 'You’re training your brain to say "yes, I can kick my pace up even though I’m tired,"' says Nurse. It’s all about forcing your brain to make the opposite decision then it wants to—and that’s a learned skill. 'Willingly embracing additional levels of discomfort takes practice,' says Fitzgerald. But the more discomfort you can withstand during training, the better prepared for it you’ll be on race day.

How to incorporate fast finish runs into your training

While anyone can benefit from fast finish runs, Nurse mostly prescribes them for half marathoners and marathoners, because those are the races where you really need to pace yourself well. 'It’s really about simulating how you’re going to feel at the end of a longer race, and getting your legs prepared for that hurt,' she says.

If you’re logging shorter mileage, it’s probably best to save this kind of workout for your longest run of the week. That said, fast finish runs aren’t the type of long runs you want to do every week. 'You want to be able to run a certain distance comfortably before you start doing it at a faster pace,' says Fitzgerald. Let’s say you have several 16-mile efforts in your marathon training. The first one should be run at an easy effort; the second or third time you run that distance, you can start incorporating some faster running near the end. Nurse typically waits a month into a training plan before scheduling a fast finish run, and then spaces them out to at most every other long run.

The most important thing to remember when incorporating these runs into your plan is to be mindful of your form. Learning to run on tired legs isn’t an excuse to get sloppy as that can increase your risk of injury. These practice runs are the time to sharpen your stride and rehearse some form checks when there is no race on the line.

Fast finish runs aren’t super taxing on the body, says Nurse, because the majority of the run should be an easy or aerobic effort. That means if you do one on Saturday or Sunday, you’ll be back on your game for speedwork on Tuesday. But fast finish runs are more race-specific, so 'you should have fewer fast finish long runs at the beginning of a training cycle,' says Fitzgerald. 'They can become more frequent the closer you get to your goal race.'

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