Timing Is Everything: All About Tempo Runs

Improving your lactate threshold is pretty straightforward: You train at or slightly above your lactate threshold. In the training schedule, I call this speed your LT (lactate threshold) pace. Training at your LT pace pushes back the point at which lactate accumulates, allowing you to maintain a faster pace for these mid-range races. How do you know what this pace is for you? If you already race in 15K to half-marathons, your race pace for those races is your LT pace. If you haven’t raced much, you can still approximate what your LT pace is. If you’ve run a 10K, your LT pace will be about 20 seconds slower per mile than your 10K race pace. If you’ve only run a 5K, your LT pace is probably around 30 seconds slower per mile than your 5K race pace is, but you should go run a 10K first anyway before trying to race a 15K to half-marathon.
Regardless of what pace you choose to shoot for, keep this guideline in mind: Your effort during LT workouts should feel “comfortably hard.” You should feel as though you’re working at a high level that you can sustain. If you were to increase your pace by 10 seconds or more per mile, you would have to slow within a few minutes.
It’s important to run as close to the right pace for as much of your LT workouts as possible. Remember what I told you in the last chapter about training to improve your VO2 max:
The biggest gains come from doing the workout in that small window where you’re most stressing the systems that you want to improve.
When you do LT workouts, you’ll probably think in the first mile that you should be going faster. After all, you’re not all that much out of breath. Stick to your pace. The point of the workout is to run it all at your LT pace. That’s different than starting out too fast, and then slowing in the second half of your LT workout. In that case, you might average the right pace for the whole workout, but never run any part of it at the right intensity. That kind of workout won’t improve your LT as much.
The classic workout to improve your lactate threshold is the tempo run, a continuous run of 20 to 40 minutes at LT pace. An example of a tempo run workout is a two-mile warm-up, a four-mile run at your LT pace, and a short cool-down jog. You can also do LT intervals. In these workouts, you do two or three intervals of a fairly long distance at LT pace, jog easily for 25 to 50 percent of the duration of the interval, and then repeat the sequence. For example, after warming up, you would run two miles at your LT pace, jog for five minutes, run two miles at your LT pace, and then do a cool-down jog.
In the training schedule, I start you with LT intervals to get you used to the workouts and to help you learn what your LT pace feels like. Once you’re familiar with your LT pace, I have you do tempo runs. Tempo runs are better because you become more accustomed to concentrating for an extended period while you’re running hard. This kind of training helps you mentally in your races.
At first, you should do LT workouts on the track or other accurately measured courses so that you have a way of checking your pace. After a few LT workouts you should have a feel for the pace. Studies have shown that most runners can accurately produce that “comfortably hard” level of effort on their own once they have learned it. This frees you to do your LT workouts on the roads or trails. Doing a five-mile tempo run on the track can get pretty boring, after all. Doing some of your LT workouts away from the track is an especially good idea if you’ll be running a hilly race because you’ll be more used to running LT pace over a variety of terrain.
Not many runners know about these workouts. They think that to run a faster halfmarathon, they should work on their speed, so they run 800-meter intervals. This type of workout does make them faster, but it doesn’t do much for their ability to sustain a pretty hard pace for more than an hour.
Those who do talk about doing tempo training throw around the words pretty haphazardly. They’ll say they’re doing an “uptempo run,” when all they mean is that they’re going to go a little harder than usual for a few miles in the middle of a run. Or they’ll go out and run a hard 10 miles and say that’s their tempo run for the week. They can call it whatever they want, but these aren’t really tempo runs. Unlike you, they don’t know why they should do these 20- to 40-minute runs at a precise pace.
Because those were workouts that I think all runners should do some version of. LT workouts are only necessary if you’re going to be doing races of 15K or longer.
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Beyond the Lactate Threshold

Put on your lab coats: It’s time for a little science lesson. As you know by this point in the book, glycogen, a form of stored carbohydrate, is your body’s preferred source of fuel for aerobic exercise. The faster you run, the more glycogen your body burns compared to how much fat it burns. Like any chemical burning process, the process of burning glycogen generates by-products. Burn paper, and you get smoke. Burn glycogen, and you get lactate. Lactate is the by-product of your body burning carbohydrates. You’ve probably heard about lactic acid. For our purposes here, that’s the same thing as lactate. Have you ever tried to sprint all-out for more than a few hundred yards? Remember how at the end of the sprint your muscles felt as though they were on fire? That’s because there was a lot of lactate circulating in your system from all the carbohydrates that were suddenly being burned to power you down the track. So much lactate was being produced that your body couldn’t clear it from your blood, so your muscles stung. Some people think that you’re damaging your muscles when you expose them to lactate.
That’s wrong. You’re always producing lactate—when you’re running easy, when you’re walking, even when you’re sitting. When you burn carbohydrates, as you almost always do, you produce lactate. Your muscles don’t ache at these low levels of effort because the rate of lactate entering your blood is equal to the rate at which it’s removed.
As you move up the intensity scale from walking to easy running, you produce more lactate, but your body also increases the rate at which it removes lactate from your blood. When you exercise above a certain intensity, however, the rate at which you produce lactate is greater than the rate at which your body can clear it.
The lactate concentration rises in your muscles and blood, and suddenly your effort feels much harder. At this point, you’ve reached your lactate threshold.
You’re probably thinking, “Thanks for the biochemistry lesson, but what does this have to do with running a 10-mile race?” Remember the basic race-training principle that I laid down last chapter: If you want to complete a race, you have to be able to cover the distance. If you also want to race the distance, then you should do workouts that improve your capacities to handle the limiting factors on your performance in that distance. For 5Ks and 10Ks, that meant doing workouts to max out your VO2 max. For 15Ks to half-marathons, that means improving your lactate threshold. Once you get past the hump of being able to cover the distance without great fatigue, the limiting factor on how fast you can run the 15K to the half-marathon is your lactate threshold. In fact, your race pace for the 15K to the half-marathon is roughly equal to your lactate threshold. Go faster than that, and you’ll start accumulating lactate in your blood. You can exceed your lactate threshold in shorter races, such as an 8K, but 15Ks to half-marathons last one to two hours for most runners, and you just can’t run that fast for that long.
To improve, then, you need to increase your lactate threshold. When you do that, your lactate threshold occurs at a higher percentage of your VO2 max. So with the right training, you can push your 15K to half-marathon pace closer to that of your 5K pace; that is, you can make better use of your basic aerobic fitness. You can run faster before you start accumulating lactate.

The Rodney Dangerfields of Races

Races of 15K (9.3 miles) through the half-marathon (13.1 miles) get no respect. The half-marathon doesn’t even get its own name; it’s just half of another distance. Imagine if people called 5Ks “half-10Ks.”
This range of races, which also includes 10-milers and 20K (12.4 miles), is almost never the focus of a runner’s races. Runners usually use these races as tune-up races a month or so before a marathon. Or some runners will run one of these races at the beginning of a racing season to build strength, and then drop down in distance to 5Ks and 10Ks for the rest of the season. But you almost never hear a runner say, “This fall, my goal is to be the best 10-mile runner I can be.”
That’s too bad. These hybrid distances can be some of the most satisfying in running. They’re plenty long, so you’re not going to get through one by running a few miles a few times a week, as you could with a 5K. But they’re not so long that they’re going to knock you down for too long. Most of the soreness and lingering fatigue that people have from marathons comes from what happens after 18 or 20 miles. Should you try a 15K, 10-miler, or a half-marathon? Why not? For people who are thinking about trying a marathon someday, building up to one of these races is a good idea. You learn the routine of training for longer distances by gradually extending your distance. Anyone running a marathon should have experience with other races first. These longer races will give you a better idea of what you’re going to experience if you try to tackle a marathon.
If you usually don’t run farther than five miles, keying on one of these races is a good motivation to extend your distance. To do that, increase the distance of your long run by one mile two out of every
three weeks. For 15Ks and 10-milers, work up to running that far two weeks before the race. Take it easy for the next two weeks, and then run the race at a strong but reasonable
pace that you know you can maintain to the end. If you’re going to do a half-marathon, then build up to 10 to 12 miles at a time, again doing your last long run two weeks before the race.
But if you’ve been running a bit more and think that you can not only cover the distance, but also run a good notch faster than on your usual training runs, you can improve your performance at these distances by entering the strange world of the lactate threshold.