There are lots of different reasons to run. Some people run to lose weight, for time in nature, or to reach a goal. But it is not likely you took up the sport of running with the hopes of plodding along, slower than your capable of, for weeks and even months.
When this blogger went to a coach to help cut down her time for her third marathon, plodding was the plan she was prescribed. Her coach freely admitted it was a hard plan to stick to and it would feel boring. But it works. It builds the runner’s aerobic capacity and endurance so that they can show up at the starting line fully trained for the distance and ready to race at a much faster pace.
But why? Why am I running one, two, even three minutes slower than my goal pace and the pace I have proven I am capable of?
Well, there are many ways the long slow distance run benefits a runner.
First, you avoid injury. Gearing up for six months of consistent and progressive training means you need to stay as healthy as possible. There are several ways to get injured during a training plan, but the most common is going too far or too fast. A marathon training plan must build mileage up, of course, so the safest way to do that is by keeping it slow while your body is adjusting to the longer runs. Then you are only stretching your abilities each week in distance, and you keep the stress on your body manageable.
During a long slow distance run, the body adapts to exercise in several ways. The body begins to build new capillaries; they bring more oxygen/blood to your hard-working muscles. Your heart gets more efficient at pumping blood; your stroke volume increases and you get more blood with every pump. You will see this evidenced by your resting heart rate going down. You also increase the mitochondria that create energy within the muscles. These adaptations occur when we mildly tax the body.
But if you stress the body by running too fast, your body must use energy to recover. If you’re running four days a week at race pace, each of the following days after your speed session your body is scrambling to recover. It has to repair the damage, and then continue with the adaptations. So if most of the week you are repairing this damage, the body doesn’t have the optimal time and energy to build new capillaries, grow the muscle of the heart, and produce more mitochondria.
There is a happy medium, where you are consistently training, increasing endurance, but not taxing your body so much that it needs intense recovery after every run. By several measures, including VO2 tests, fat metabolizing tests and HR tests, this sweet spot seems to be 65-75% of your max speed. At that rate you can still have a conversation with your training partner. You’ll feel fatigue but not until a hill or the end of a long run. What you may feel is a little bored.
A big part of running is self-discipline and endurance. Sometimes a slow run is a practice of discipline. You must discipline yourself to run slower and endure a longer run because of that slower pace. But you are still making progress, and you’ll feel it at your next start line.