Here’s How To Crush Your Next Trail 10k

From the time the ancient Greek runner Pheidippides ran from Marathon to Athens to announce the Greeks’ victory over Persia in the Battle of Marathon, humans have been fascinated by endurance. And today’s trail runners have hundreds of race options in which to test their mettle, e.g. the Wissahickon Trail Classic 10K in Philadelphia, Pennsylvania, the Tecumseh Trail Marathon in Bloomington, Indiana, and the Western States 100-Mile Endurance Run in Northern California. The key to racing well is knowing how to train the three main factors affecting endurance performance— VO₂max (aerobic power), lactate threshold, and running economy—for your chosen race distance, from 10K to ultramarathon.

VO₂max (Aerobic Power)

VO₂max is the maximum volume of oxygen that your muscles can consume per minute. To be a good distance runner, you need a high VO₂max. Think of VO₂max as your VIP card—a high VO₂max alone gains you access into the club. But having that VIP card is not enough. To be a great runner, you need to have other tools in your physiological arsenal.

Lactate Threshold

One of those other tools is the lactate threshold (LT). The LT demarcates the transition between running that is almost purely aerobic and running that includes significant anaerobic metabolism. (All running speeds have an anaerobic contribution, although when running slower than LT pace, that contribution is negligible.) Thus, LT is an important determinant of endurance performance since it represents the fastest speed you can sustain aerobically without a significant anaerobic contribution. Research has shown that LT is the best physiological predictor of distance-running performance.

Running Economy

A third tool is running economy, the volume of oxygen (VO₂) used to maintain a given speed. The less oxygen you use to run at a specific speed, the better. For example, if two runners have the same VO₂max, but Runner A uses 70 percent and Runner B uses 80 percent of that VO₂max while running at eight-minute mile pace, the pace feels easier for Runner A because he is more economical.

Therefore, Runner A can run at a faster pace longer before feeling the same amount of fatigue as Runner B. Running economy is influenced by biomechanics, the proportion of slow-twitch muscle fibers, body weight and the density of mitochondria, microscopic structures responsible for aerobic metabolism.

10K Training

The emphasis of 10K training is on lactate threshold, VO₂max and the ability to withstand a fast pace. However, whether you’re training for a 10K or ultramarathon, it all starts with mileage. That’s because endurance training stimulates many physiological, biochemical and molecular adaptations. All of these adaptations can be thought of as your body’s attempt to cope with the demand placed on it by running every day. For example, endurance training stimulates more fuel (glycogen) to be stored in your muscles, increases the use of intramuscular fat at the same speed to spare glycogen, increases the size of the left ventricle of your heart so that it can pump more blood (and oxygen) with each beat, improves your blood vessels’ oxygen-carrying capability by increasing the number of red blood cells and hemoglobin, and increases your muscles’ capacity to use oxygen.

Lactate Threshold (LT) Runs

You can improve your LT by running at your current LT pace. Increasing your LT pace allows you to run faster before you fatigue, because it allows you to run faster before anaerobic metabolism begins to play a significant role. The benefit to being able to run aerobically at 7:00 pace compared to 7:30 pace is obvious.

With my athletes, I typically use three types of LT workouts:

• Continuous runs (2 to 5 miles) at LT pace;
• Intervals run at LT pace with short rest periods, such as 4 to 6 x 1 mile at LT pace with 1-minute rest; and
• Shorter intervals run at slightly faster than LT pace with very short rest periods, such as 2 sets of 4 x 1000 meters at 5 to 10 seconds per mile faster than LT pace with 45 seconds rest and two minutes rest between sets.

LT pace is about 10 to 15 seconds per mile slower than 5K race pace (or about 10K race pace) for runners slower than about 40 minutes for 10K (about 80- to 85-percent maximum heart rate). For highly trained and elite runners, the pace is about 25 to 30 seconds per mile slower than 5K race pace (or about 15 to 20 seconds per mile slower than 10K race pace, or about 90-percent maximum heart rate). Subjectively, these runs should feel comfortably hard. (Please see “Have a Heart,” Training, Issue 53, August 2008 for information on determining your maximum heart rate.)

Long Intervals

Long intervals (3 to 5 minutes) increase the heart’s stroke volume and cardiac output, leading to an increase in VO₂max. Research has shown that high-intensity training (95- to 100-percent VO₂max) is the best way to improve it. Regardless of the length of the intervals you choose, you should run them at the speed at which VO₂max occurs (referred to as the “velocity at VO₂max,” or vVO₂max), which is approximately 3000-meter (or 2-mile) race pace for highly trained runners. If you run 3000 meters in longer than about 10 to 11 minutes, however, your vVO₂max will be between mile and 3000-meter race pace. If using heart rate as a guide, you should come close to reaching your maximum heart rate by the end of each interval. You can also do hill repeats on a trail in place of intervals on the track to serve as a transition into more formal interval training.

Short Intervals

While long intervals are the most potent for improving VO₂max because you repeatedly reach and sustain VO₂max during the work periods, short intervals (1 to 2 minutes) run at vVO₂max can also improve VO₂max, as long as you use short, active recovery periods to keep VO₂ elevated throughout the workout. Short intervals run at mile race pace will help you address the anaerobic component of the 10K by increasing the number of enzymes involved in anaerobic metabolism and your ability to buffer the acidosis that results from high-intensity running.

10K Training Program

Program is planned in four-week cycles, with the fourth week used as a recovery period. Cycle 2 includes a slight decrease in mileage to accommodate an increased intensity. Numbers represent miles. LT = lactate threshold; vVO₂max = velocity at VO₂max.

Dr. Jason R. Karp has a Ph.D. in exercise physiology, and is director and coach of REVO2LT Running Team, a freelance writer and competitive runner. He writes for numerous international running, coaching and fitness magazines. He has coached high-school and college cross country and track and field, and currently coaches athletes of all levels and consults with fitness professionals through Run-Fit.com.