The many benefits of long runs
By Matt Fitzgerald
Dec. 6, 2006 -- Categorically speaking, long runs are moderately to highly challenging workouts that are taxing for their duration more than they are for their intensity. Long runs are more important than high-intensity run workouts such as speed intervals and tempo runs because without long runs you wouldn't even be able to finish a middle-distance or long-distance triathlon, whereas high-intensity run workouts only help you finish faster, supposing you already have the endurance to finish.
Long runs are performed at any pace between an easy jog and marathon race pace (60 to 85 percent VO2 max). Therefore some of the benefits that come from doing long runs are the same as those associated with shorter runs performed within the same intensity range. What qualifies as a long run when you're training for sprint triathlons is unlikely to qualify as a long run when you're training for an Ironman. But one thing is absolute: every triathlete needs runs that are long for him or her, today.
General benefits
Long runs enhance your ability to handle the repetitive impact of running without getting injured by increasing the density of the bones of your lower extremities and creating thicker, tougher tendons and stronger, more rupture-resistant muscle fibers. Precisely because they last longer than other workouts, long runs advance these crucial adaptations further, as long as you build up to them gradually.
A second benefit that long runs share with other run workouts is that of improving your running economy. The more time you spend running, the more waste your neuromuscular system is able to remove from your stride. The two factors that determine how much time you spend running are, of course, the frequency of your runs and their duration. For this reason long runs are among the best economy-boosting workouts.
Two further benefits that are associated with, but not particular to, long runs are increased aerobic capacity and enhanced aerobic metabolism. Your aerobic capacity is the maximum rate at which oxygen can be delivered to your muscles. A host of distinct adaptations serve to increase aerobic capacity; these include growth of the heart muscle and increases in blood volume, hemoglobin in the blood, and capillary density in the muscles.
Aerobic metabolism is the process by which energy is released from glucose, glycogen, fatty acids, and amino acids with the help of oxygen inside your muscle cells. As with aerobic capacity, there is a whole list of adaptations stimulated by moderately low- to moderately high-intensity running that serve to increase your capacity for aerobic metabolism. These adaptations include an increase in the number of mitochondria (the organelles inside your muscle cells wherein aerobic metabolism occurs) and an increase in the activity of the enzymes that facilitate the oxidation of glucose/glycogen and fatty acids.
Particular benefits
There are additional benefits of long runs that are more particular to this type of workout. The most celebrated special benefit of long runs is that of delaying exhaustion due to liver and/or muscle glycogen depletion. Moderate-intensity running enhances fat burning, allowing you to burn less glycogen and thereby conserve it longer. Long runs that deplete glycogen stores also stimulate higher levels of subsequent glycogen storage, in effect giving you a bigger gas tank to work with. Finally, long runs enhance your body's capacity for gluconeogenesis - that is, for converting lactate and amino acids into glucose in the liver. This allows you to keep running strong even when your original glycogen stores have fallen low.
Muscle damage is another major cause of fatigue in long runs that you can become more resistant to by regularly doing challenging long runs in training. Individual muscle fibers are susceptible to rupturing as they contract eccentrically to keep your body from crumpling to the ground every time your foot lands. As this damage accumulates, your form falls apart, your nervous system cuts back on muscle stimulation, and you start to feel sore and miserable. In a word: you bonk. Long runs increase the muscles' capacity to survive repetitive eccentric stress and thereby delay the point at which muscle damage reaches a critical, bonk-inducing level.
Tips for long runs
Start doing long runs once a week beginning about six weeks into your training program and continue doing them throughout the remainder of it. Skip the long run during recovery weeks, which you should indulge in every third or fourth week.
Your first long run should be just 10 percent longer than the longest run you've done up to that point in your training program. Increase the duration of your long run by up to 10percent with each subsequent iteration. Aim to do your longest long run 4-12 weeks before your last or longest race of the season. Four weeks is best if it's a long-distance race or any race wherein your goal is just to finish. Closer to 12 weeks is better if you're training to be competitive in shorter triathlons. After that point your long runs can level off and you can focus more on high-intensity workouts.
While you're increasing the duration of your long runs, do them at a comfortable pace. Just going the distance is enough to stimulate the adaptations you seek. The danger of doing your long runs too fast is that your muscles will be forced to burn carbohydrate preferentially, foiling your objective of increasing your fat-burning efficiency. When your fitness reaches the point where just covering the distance is no longer challenging, you can start to push the pace and do some variable-pace long runs. The two conventional formats for the variable-pace long run are (1) starting slowly and increasing the pace every few miles throughout the run and (2) throwing some marathon-pace or tempo-pace surges into an otherwise easy long run. Save these tough workouts for the final weeks of your training program.
Wear a fluid belt on all your long runs and drink a sports drink throughout them. This will enhance your performance in these workouts and in so doing enhance the training effect you derive from them. It will also help you recover faster from your long runs, especially if you use a sports drink containing amino acids or protein. If you just can't be bothered to carry a bottle, at least carry gel packets and find water fountains where you can wash them down.