Posted by Dave on July 11, 2011 | 8 CommentsThis summer I’m reading Tim Noakes’ massive volume Lore of Running, bit by bit, then reporting the critical bits back to you. Last week I covered VO2 max, the idea that every runner can consume a relatively-fixed maximum amount of oxygen. But while VO2 max can’t be improved much with training, I held out hope that running efficiency (referred to in the scientific literature as “economy”) can be.
Unfortunately, Noakes spends the remainder of the chapter making a fairly strong case that even running efficiency can’t be improved much. Noakes argues that a distance runner’s performance in events longer than 5K is almost perfectly predicted by her or his performance in the 5K. Thus, the preponderance of tables and calculators all over the internet predicting your marathon time based on your best 5K time, or your time for any other distance. For example, I can visit the McMillan Running Calculator and input my 5K PR of 21:32, and it will spit out my projected times for every distance from 100 meters (18.3 seconds) to a marathon (3 hours and 29 minutes). Of course, I prefer to enter my 8K PR, which gives me a projected marathon time of 3 hours and 23 minutes!
McMillan takes pains to point out that you can only achieve your projected times if you train for the particular race; if you have only trained for a 5K and your PR is 21:30, you’re not going to go out tomorrow and run a three and a half hour marathon — you have to do your best job training for the marathon first.
A lot of people take a look at something like the McMillan calculator and start thinking about hypotheticals: “If I can get my 5K time under 20 minutes, that means I could run a 3:15 marathon!” Noakes suggests that’s the wrong way of thinking about it. Your 5K pace isn’t going to improve a whole lot, he argues, because at that pace you’re running at about 95 percent of VO2 max, and, if you recall, it’s very difficult to improve your VO2 max. All training will do, Noakes seems to be saying, is allow you to attain your maximum potential given your (relatively) fixed VO2 max. Just as some runners have genetically higher VO2 max, some runners are genetically more efficient than others, and just as you can’t do much to improve VO2 max, Noakes claims, you can’t do much to improve efficiency, either. Efficiency, Noakes says, has a bit to do with your stride length and how much you bounce up and down while you run, but other than that, it’s primarily due to genetic factors like your muscles’ ability to store energy and resist fatigue. Is that really true?
I find all of this rather confusing, and I expect you might too, if you’ve ever progressed from a relatively unfit phase of your life to a more-fit phase. A year and a half ago, I ran an 8K in about 43 and a half minutes. This year, I ran one in 34 minutes, improving by nearly 22 percent. If VO2 max can only improve by 5 to 15 percent, how is that possible?
The reason is simple: These tables are based on individuals who are trained to their maximum potential. If you’re completely out of shape and you try to run a 5K, you probably won’t be able to finish without walking most of the distance. You might not be able to finish at all. Suppose you manage to complete the race in 50 minutes. McMillan’s calculator dutifully predicts you’ll finish a marathon in 8:07:26, an average pace of 18:37 per mile, which is no more than a brisk walk. But I guarantee you, if you spend the next year training and avoid injury, you’ll be able to complete a marathon (and a 5K, for that matter) much faster than that. In other words, if you’re not already in the best shape you can possibly be in, these fitness calculators tell you very little about your potential.
Elite marathoners typically are extremely lean, about 4 to 7 percent body fat for men, and 6 to 15 percent for women—about half the level of the average person. Many people with anorexia have more body fat than that! (However, as Dan points out in the comments, although some runners do suffer from anorexia, a true elite marathoner manages his or her diet properly and can safely maintain a lean body mass)
and bordering on some definitions of anorexia. If you have, say, 35 percent body fat, you can get a whole lot fitter just by losing some of your excess body fat; there’s no way a pace-predictor can account for that. This isn’t to say losing that weight will be easy—but it’s not impossible! What is more difficult is determining when you’re as fit as you can be. You can always lose more weight, but at some point losing weight becomes unhealthy.
So despite the somewhat fatalistic statements in this section of Lore of Running (I’ve only read through page 91 out 930), most runners will be able to improve considerably through training. While it is true that few of us have the potential to be elite runners, nearly everyone can be much better than they are now.
What this means for you: Running pace predictors can be good fun, and they can be useful for making short-term goals. But unless you are already in top shape, they don’t define absolute limits for performance. Nearly everyone can improve through training.