**This post is one of several in an excerpt series from the book, Be a Better Runner by Sally Edwards & Carl Foster**
The Black Hole for Runners
It turns out that very fast runs are good for you—and that moderately fast runs (those just above threshold, in the Black Hole) are not. That’s because Black Hole runs are too slow to cause enough stress to make your body want to strengthen itself, and too fast to allow you to go long enough to improve your endurance. Studies of top runners find that they (by design or not) minimize their time in the Black Hole.
How fast is the Black Hole? In terms of pace, heart rate, and the Heart Zones chart, the Black Hole is actu- ally a very narrow band. It starts at threshold, right as you enter Zone 5, and goes about 5 percent higher. So, if your threshold heart rate is 150 bpm, your Black Hole would extend from 150 to 157 bpm. That means if you really want to improve, your fast runs should roughly start at a second threshold: 158 bpm.
Using Heart Rate Training to avoid it
In the Heart Zones Threshold Training System, there are actually two thresholds: The first threshold line is known as T1 and the second threshold line is T2. Therefore, your goal with the training described in this book boils down to this: Stay above T2 and stay below T1. Stay out of the Black Hole. (Or, in terms of the Heart Zones chart shown above, stay out of Zone 5a, the first part of Zone 5, which you will see is divided into three sections, 5a, 5b, and 5c.)
The Black Hole is only five to ten heartbeats per minute wide, depending on your fitness, but staying out of it will not be as easy as it sounds, because it turns out that most people love to run there. Why? Well, the Black Hole is just hard enough that it makes them feel like they are doing themselves some good. Run in the Black Hole all the time, as most people do, and you end up tired, but no faster.
Your heart rate monitor is an invaluable tool in the Heart Zones system because, besides being interesting and fun, it gives you real numbers to attach to T1, T2, and the Black Hole.
Keep in mind that those numbers will increase over time as your fitness improves—which is a big advantage of Heart Zones over other systems. It’s dynamic; it accurately reflects you as you are now, and it changes as you do.
More to come ..
Keep your eyes peeled as we continue to release excerpts throughout upcoming weeks. If you fall in love with these tips from our excerpt series, make sure to stop in and grab a copy of Be a Better Runner from our online store, and keep it on your shelf at home to reference and share with others!