And when it’s better to hold back.
By Cindy Kuzma
You’ve completed a few half marathons, and your sights are set on a new goal: breaking two hours. You download a training plan designed to help you do just that.
That’s when you notice something unusual: While the half marathon distance is only 21.2km, the long run on this plan reaches up to 22.5 kilometres. There is a reason for this particular type of runner math.
The first time you tackle a new distance—or if you’re training for a marathon (or an ultra)—you probably won’t touch your goal distance in training, Jessica O’Connell, an Olympian in the 5,000 metere, exercise physiologist, and owner of Fast Forward Run Coaching, tells Runner’s World.
But there are times when, for distances from 5K to the half marathon, it makes sense to overshoot your race-day mileage during one or more of your weekly long runs. Here’s what to know about when to go (even) long(er), and when to hold back.
The Benefits of Having Longer Long Runs in Your Training
Running longer distances at relatively easy paces improves your aerobic fitness, meaning your cardiovascular system more efficiently shuttles oxygen-rich blood through your body, O’Connell says. As you put in the kilometres, you also grow more capillaries—tiny blood vessels that provide oxygen and other nutrients to your muscles—as well as mitochondria, the energy production factories within muscle cells. This eventually makes running longer, and faster, feel easier.
You’ll also boost what’s known as your running economy, or how fast you can run using a given amount of oxygen, she notes. And becoming a more efficient runner also contributes to faster race times.
In addition, you’ll increase your body’s ability to store glycogen, your muscle’s primary fuel source, says Kelcie VanGampleare, P.T., D.P.T, a board-certified clinical specialist in sports physical therapy and spokesperson for the American Physical Therapy Association. You’ll therefore be able to better maintain energy levels throughout a race, and ward off bonking or “hitting the wall.”
At the same time, long runs train your body to more efficiently tap into other fuel sources, including fat. “This may allow for longer periods of training prior to fatigue setting in,” VanGampleare says.
When your muscles do begin to tire, longer long runs can improve your ability to keep going (within reason—you shouldn’t push through pain, injury, or severe fatigue, she says).
And then there’s the mental benefit. “You see individuals being more confident in their ability to perform at a race if they’ve already done that distance,” says VanGampleare, who works with Olympic and Paralympic athletes. “It’s kind of like: ‘I can do it because I’ve done it before.’”
Why Go Beyond Race Distance for the 5K or 10K
The benefits of longer long runs are clearest for shorter distances, says Anh Bui, D.P.T., C.S.C.S., a former collegiate runner, certified running coach and owner of Run Resiliently Physical Therapy. If you’ve already raced a 5K or 10K at least once, exceeding it in your training will likely help you take your performance to the next level.
Unlike sprints—efforts shorter than two minutes where your body produces a burst of energy without oxygen—the 5K and 10K are primarily aerobic races, albeit fast-paced ones. Adaptations to your aerobic system increase significantly as you extend your long run from about 30 minutes to 60 minutes or more, O’Connell says. In fact, it’s not unusual to see advanced 5K or 10K runners logging long runs of up to 15, 20 or even 25 kilometres.
Of course, the long run is only one piece of the training puzzle. Your week should include other runs, such as shorter recovery runs, hills, and interval workouts. Ideally, your long run should be no more than about 30 percent of your total weekly volume, though there are other factors to consider, O’Connell says.
But long runs are a particularly strong stimulus, even if your goal race is shorter. In addition to building your aerobic engine so maintaining a fast pace at shorter distances feels easier, they also prepare your musculoskeletal and cardiovascular systems to handle additional types of training, such as speed workouts, that can further enhance your performance, Bui says.
The Equation Changes for the Half Marathon
Building up the long run over time is essential for anyone completing a 21.1 kilometre race. In addition to improving your aerobic fitness and preparing your muscles, tendons, and joints to go the distance, long runs allow you to practice taking in fuel on the run, Bui says. That’s helpful for any efforts of an hour or longer, and critical for those lasting 90 minutes or more.
You don’t have to go overboard for your first half marathon (or the first few). Long runs of 15, 16, or 20 kilometres will more than prepare you for the challenge, Bui says. Come race day, the combination of your total training volume, a smart taper, good nutrition, and race-day vibes will carry you the remainder of the distance across the finish line, O’Connell says.
However, you can continue reaping additional aerobic benefits from longer long runs, at least up to about two and a half to three hours. So for advanced runners, going beyond 21.1 kilometres during half marathon training could improve your fitness and race performance. (Bui, who has a half marathon PR of 1:24, has done up to 28 kilometres in a half marathon training block.)
That’s provided you’ve already run at least one half marathon, are regularly running four to five times per week, and have time in your training schedule to build up safely—O’Connell typically adds no more than 1.5 kilometres, or five to 10 minutes, to the long run each week, with occasional cut-back weeks. To keep that slow progression, you need to make sure you have the time to build up to more than 21.1 kilometres ahead of race day.
A note of caution: You can reach a point of diminishing returns if you go too long. “You’re putting a lot of load on your body, and then asking your body to recover,” VanGampleare says. If you’re still dragging after a long run heading into your next week of training, you risk overtraining and injury. That’s a big reason why even the most elite marathoners rarely run 42.2 kilometres, and even fewer run longer, in training; there just isn’t enough time to recover and get back to work.
Test if a Long(er) Run Works for You
Even if you choose a training plan that builds to a longer long run, monitor your progress and make sure your body is adapting. “My rule of thumb is that you should recover from each one of your sessions within two days,” Bui says. If you’re sore and fatigued for four days after a 22 kilometre run, that distance might have been a stretch and you’d be better served by dialing back a bit.
“When people follow a training plan, I think my best advice would just be, everything’s written in pencil,” Bui says. After all, you’re far more likely to have a great race if your half marathon long run maxes out at 16 kilometres but you’re healthy and happy, versus if you push longer through pain or burnout.
“The biggest skill for a runner, in terms of staying injury-free and getting to the start line, is knowing when to pull back,” Bui adds.
