“Junk miles.” Remember that buzzword from a few years ago? There were lots of books and articles advocating that runners cut out easy miles on the theory that you get more bang for your buck with high intensity running, and it was those extra easy miles that were hurting you and causing injuries. The theory has some intuitive appeal, I suppose. If you cut out easy miles, you reduce your overall mileage and, therefore, take fewer steps, but you still get the benefits of the key workouts.
If you’ve read this blog for very long, you know that Penny and I have personally disproven the anti-junk-mile theory of training. On more than one occasion, we’ve considered changing our blog name to Two Always Injured Runners. But we never get injured when we are in the base-building phases of our training plans, when we are running easy paces and working on increasing our mileage. No, base building always feels great! Our injuries have always occurred when we add speed – too much speed.
A few months ago, I read Matt Fitzgerald’s new book called 80/20 Running. He argues that the most effective training is for runners to spend 80% of their cardio time at easy paces and just 20% at moderate to hard paces.
He supports the 80/20 rule with citation to studies showing that VO2 max and 10K race times in well-trained runners improved the most when they followed the 80/20 rule compared to control groups spending higher percentages of time at moderate to high intensities (70/30, 60/40). And the runners in 80/20 groups also had fewer incidence of injury and reported higher energy levels for day-to-day tasks (like working and all those other non-running obligations that fill up our lives). Anecdotally, Fitzgerald also examined training plans of the most successful elite runners, and they all basically follow the 80/20 rule. I’ll let you pick up the book to read about the details of the proof.
A few comments about the three bolded terms above for implementing the 80/20 rule:
First, “cardio time.” All cardio training, not just running, counts. So if you are doing intense spinning classes, those hard minutes count toward your 20%.
Second, “easy paces.” Easy pace is slower than you think. Basically, you’re running an easy pace for purposes of the 80/20 rule when you are below the ventilatory threshold – i.e., the pace at which you can still easily talk. The book gives a few different ways to calculate this pace. The easiest way is to find the pace at which you can recite the Pledge of Allegiance without straining (for our Aussie readers, that’s about 7 or 8 seconds…1-one thousand, 2-one thousand, 3-one thousand, 4-one thousand, 5-one thousand, 6-one thousand,7-one thousand). For any cardio cross-training (e.g., elliptical, cycling), you use your heart rate at your ventilatory threshold pace minus 10 beats per minute.
Third, “moderate to hard paces.” Any workout time above the ventilatory threshold counts toward your 20%. Fitzgerald says that the most effective way to spend your 20% (e.g. short intense efforts, longer threshold efforts, or a mix) is still being studied. The training plans in the book use a mix of progressions, fartleks, tempos, and speed intervals – just like most training plans do.
Although I’m not as fit as I’ve been in the past, I think about each of my easy runs (which has been virtually all of my runs in the last 4 months) as rebuilding my fitness and beyond – to better than it has ever been before.
Two Little Runners ~ Kristen