Guide for 10K through ultramarathons
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.
Photo by Chet White
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.
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.
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.
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: 1) continuous runs (2 to 5 miles) at LT pace; 2) 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 3) 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 (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.
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.
In a marathon, the main difference from shorter races is that you run out of carbohydrate, which is your muscles’ preferred fuel. You have enough stored carbohydrate (glycogen) in your muscles to last slightly more than two hours of sustained running at a moderate intensity. So, unless you plan on running the marathon as fast as Haile Gebrselassie, you’re going to run out of fuel. Glycogen depletion and the accompanying low blood sugar (hypoglycemia) coincide with hitting the infamous wall.
Other issues not encountered in shorter races that affect marathon performance include dehydration, muscle-fiber damage, increased body temperature (hyperthermia) and psychological fatigue. When you sweat a lot, you become dehydrated, which causes a decrease in the plasma volume of the blood, decreasing the heart’s stroke volume and cardiac output. Oxygen flow to your muscles is then compromised, and the pace slows.
The relentless pounding causes muscle-fiber damage, which decreases muscle-force production. Since your muscles produce heat when they contract, running for long periods of time increases body temperature and the resulting hyperthermia decreases blood flow to the active muscles since more blood is directed to the skin to increase convective cooling. Finally, running for so long can cause psychological fatigue, the latter of which is due to changes in the levels of brain neurotransmitters.
While high mileage is important for the 10K, it is especially important for the marathon to maximize your aerobic capacity. This may even require running twice per day to spread out the stress and maximize recovery. In addition, research has shown that runners who perform high volumes of endurance training tend to be more economical, which has led to the suggestion among scientists that running high mileage (greater than 70 miles per week) improves running economy.
Running’s repetitive movements result in improved biomechanics and muscle-fiber recruitment. Additionally, economy may be improved by the weight loss that usually accompanies high mileage (a lighter body needs less oxygen than a heavier body); the growth of slow-twitch skeletal muscle fibers; and the greater ability of tendons to store and use elastic energy with each step.
The main difference between 10K training and marathon training is the inclusion of long runs in your program, with the amount of time spent on your feet being more important than the number of miles you cover. Repeatedly running for more than two hours presents a threat to the muscles’ survival by depleting their store of glycogen. However, the human body responds rather elegantly to situations that threaten or deplete its fuel supply: It synthesizes and stores more than what was previously present, thus increasing endurance for future efforts. Empty a full glass, and you get a refilled larger glass in its place. Much like college fraternity parties. The more glycogen you have packed into your muscles, the greater your ability to hold your marathon pace to the finish.
If you’re training for a trail marathon, do most of your long runs on trails so you get used to the uneven terrain, and run in trail-running shoes. While your long run should not comprise more than about 30 percent of your weekly mileage, this rule can be broken if you are only able to run a few times per week. Run at a comfortable, conversational pace (about two minutes per mile slower than 5K race pace, or about 70 to 75 percent of maximum heart rate). Lengthen your long run by one mile each week for three or four weeks before backing off for a recovery week.
If you run more than about 40 miles per week, or if you run faster than about eight-minute mile pace, you can add two miles at a time to your long run. Keep adding miles until you reach 22 to 24 (or about 3 to 3½ hours, whichever comes first), and do your longest run two to three weeks before your marathon.
Lactate Threshold (LT) Runs
LT runs are also very important when preparing for the marathon. The longer the race you’re training for, the more important it is to train your LT, because the closer the race pace will be to your LT pace and the more important it becomes to hold a hard pace for an extended time. And for a marathon, you need to extend the duration of your LT runs. To accommodate the increased duration, you can run a bit slower than LT pace (which I call tempo runs). Since optimal marathon pace is only about 15 to 20 seconds per mile slower than LT pace (with the difference in paces getting larger as performance level declines), the goal of marathon training is to raise your LT and to increase your ability to sustain as high of a percentage of your LT as possible.
If you’re experienced with doing many long runs and want to give your marathon performance a boost, try inserting LT-paced running into some medium-long runs (12 to 16 miles). These LT/LSD (long slow distance) combo runs simulate the physiological and psychological fatigue of the marathon. Like long runs, they severely lower muscle glycogen, stimulating its synthesis and storage. You can include LT segments at the beginning, middle and/or end of the run. Some examples are: 1) 4 miles at LT pace + 8 miles easy; 2) 5 miles easy + 3 miles at LT pace + 5 miles easy + 3 miles at LT pace; and 3) 10 miles easy + 4 miles at LT pace. After you’ve done a number of these combo runs, try running faster than LT pace for the last mile or two of the final LT segment, which will sharpen you for the marathon. For example, run 9 miles easy + 4 miles at LT pace + 1 to 2 miles faster than LT pace. You may want to run the LT segments on a track, where you can closely monitor your pace. Because these workouts are very tough, alternate the long run with the LT/LSD combo run every other week, and after three or four weeks, don’t do either run for one recovery week.
While both the marathon and ultramarathon require the largest glycogen storage capacity possible, and a very efficient capacity to make new glucose and use fat, they are paramount for the ultramarathon. Therefore, one of the goals of ultramarathon training is to teach your muscles to rely on fat as fuel. While muscles’ store of carbohydrate is limiting, the human body’s fat store is virtually unlimited, with enough to fuel about five days of marathon running or about 1000 miles of walking. While women are at a cardiovascular disadvantage in that they have a smaller cardiac output and less hemoglobin in their blood to transport oxygen, research has shown they have a greater capacity to metabolize fat and conserve glycogen, which may give them an advantage for very long endurance activities. Indeed, in 2002 and 2003, Pam Reed beat all the men at the 135-mile Badwater Ultramarathon.
Very Long Runs
There are two ways to make your muscles more effective at using fat for energy: 1) run/walk for very long periods of time (4 to 6 hours); and 2) begin your runs with low muscle glycogen by consuming a low-carbohydrate diet for a couple of days before each long run. When you threaten the survival of muscles by depriving them of their preferred fuel, a strong signal is sent to combat the threat and use other fuel sources more effectively. The downsides to training with little glycogen, however, is that 1) it doesn’t feel good; and 2) it compromises your intensity level since fast running depends on carbohydrates for fuel. If you’re going to try training with low muscle glycogen, make sure you consume lots of carbohydrates before your ultramarathon, so you “train low, race high.”
Given its duration, the ultramarathon also requires you to consume calories during the race. If you’ve ever eaten during a long endurance event, you know the mess it can make of your digestive system. Practice eating different foods in training to see what your stomach can handle.
Like the marathon, dehydration, muscle-fiber damage, hyperthermia and psychological fatigue are huge issues for the ultramarathon, so use long runs to practice dealing with them. Since your sweat rate exceeds your ability to ingest fluid while running, dehydration is difficult to prevent. However, since endurance performance declines with only a two- to three-percent loss of body weight due to fluid loss, it’s important to minimize its effects by drinking fluids with sodium. More water is conserved by the kidneys when you ingest sodium with the water.
Climate has a greater effect on the ultramarathon than it does on any other race. Depending on your chosen race, prepare yourself by acclimatizing to hot and humid conditions beforehand. While cardiovascular adaptations to running in the heat are nearly complete within one week, the sweating response takes about two weeks, so give yourself at least two weeks of slowly introducing yourself to the heat.
The next time you train for a 10K, marathon or ultramarathon, follow these training guidelines. And if you train smart enough, not only will you increase your fitness, you may even be able to chase Pheidippides.
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 RunCoachJason.com.