Pace Calculator Issues

>> Tuesday, January 31, 2012

This is not a rant. Repeat: this is NOT a rant. I don't get "fired up" about this, but it's just worth noting. And none of this is "ground-breaking" info - just my take on the topic.

Before the half marathon on Saturday, I was told by 2 people that I SHOULD be able to run a sub-1:20 half marathon based on my recent Meet of the Miles 1-mile time. And that's part of why Chad called me a sandbagger with my DREAM GOAL of a 1:25 finish. I hoped I could go 1:25, but sub-1:20 would have been impossible. But the numbers SAY I should be able to do that.

Here's what they're talking about: here are my equivalent race times from the McMillan Running Calculator that many of you are familiar with:

My 13.1 equivalent performance based on my 4:53 mile

The problem with that is that these predictions assume you've trained up for that distance in the same way you trained for the shorter run. Here's what it says on their site: "Do keep in mind that a 5K runner is unlikely to run the equivalent time in the marathon off of 5K training. The runner would obviously need to train for the marathon to accomplish this equivalent time." This is all obvious, but when I'm only putting in 20-25 miles / week (a lot of that in the past was pushing a stroller at Henry's pace), I can bust out a speedy 1 mile, but there's no way I can just say "Yep, now I should be able to run a 1:18 half." Also, if I trained the same way for the half as I did for the 1 mile, I'd get soooo injured soooo quickly. I cannot run as many miles as McMillan wants me to without getting hurt.

Just because I'm stupid, let's really test the McMillan Running Calculator. There are plenty of people on this planet right now that can run a 10-second 100 meters. According to McMillan, they'd SHATTER world records at the marathon distance if they "trained" for it:

A 1:54 MARATHON time for those that can do a 10 sec 100. Yeah, no prob.

Sure, that's a little "out there" of an example. But what about using Ryan Hall as an example. In April of 2011, Hall ran the Boston Marathon in 2:04:58. Then, in May, he came to town to run the TC 1 Mile. Here I am with Ryan and Sara Hall a few hours before the race:

The pace calculator said that he should be able to run a 3:42 mile based on his recent marathon time:

But Hall ran a disappointing 4:17.2 (and finished last place in the elite wave). That's a big difference.

And this highlights my issue.

Ryan Hall is "distance" trained, and he couldn't pull that speed out of his legs on his distance training.

I have a bit more "speed," but I don't have the endurance, so I can't run the longer races as fast as this calculator says I "should" be able to. I simply don't put in the miles. (Oh, and I'm NOT saying I have more speed than Hall... I just might have more "speed vs endurance" whereas Hall has more "endurance vs speed" based on our own abilities.)

I started this post by saying "this is not a rant" (even though I'm using the "rant" label at the bottom of this post), and what I mean is that I'm never really annoyed when people think I can run something at a certain pace because this calculator says I should be able to. It IS a good thing to look at when comparing the difference in some races. I use it quite often.

But the more miles between the comparison, the farther off it can be. You could get a good sense of your 5K time based on a 1 mile race (that's over 3x the distance, but it's only about 2 miles more). Same with comparing a 5K to get an anticipated 10K finish (2x the distance, and only 3.1 miles more). But a half marathon to a marathon is quite a jump - that's SUBSTANTIALLY different training that McMillan is asking you to do in order to hit their predicted time.

That's not all bad. And it's kinda obvious. But if you're just comparing possible race outcomes without MAJORLY changing your training, then it won't give you 100% accurate answers. And that's kinda where I fall. I didn't change many workouts going into the 1 mile race, and I just made sure to get in some long runs before my half marathon. All the "middle stuff" was about the same.

* * * * * * * * * * * * * * * * * * * * * * * *

I talk to Coach Jen about some of these issues in this post from Sept of 2010. Here's just part of that post:

Here are some other numbers to back up my points. Below are 3 screenshots from the McMillan Running Calculator. They show my estimated times based on my back-to-back-to-back races this past spring: a 5K, a 4 mile, and a half marathon:

Estimates based on my 17:11 5K

Estimates based on my 22:42 4 mile

Estimates based on my 1:22:52 half marathon

Notice: My 5K time says that I could do a half marathon in 1:19:26, but that’s WAY FASTER than I could do.

On the flip-side, my half marathon time says that I should do a 5K in 17:56, but that’s WAY SLOWER than I just did.

I can go shorter and harder, but when I go longer, I end up easing back a little. (And I know, the McMillan Running Calculator is NOT an exact science. I HAVE heard things about needing to run a ton of miles to be able to hit your predicted McMillan times.)

BUT, for what it's worth, notice that the difference in a predicted marathon time between those 3 screenshots is just over 7 minutes... 7 minutes isn't THAT big of a difference in a marathon. At least I don't think so. I'd LOVE to have any of those times in a marathon!

And to make one more point in DEFENSE of the pace calculator: note the different 10-mile times it gave me above based on my 3 races: 59:49, 1:00:24, and 1:02:24. Those 3 races were in the spring of 2010, and I ran my best TC 10 Mile in the fall of 2010. I've been saying that I'm faster at the shorter races, so my 10-mile time SHOULD be somewhere between my 4-mile prediction of 1:00:24 and my half marathon prediction of 1:02:24. But being I worked with Coach Jen for 2 months leading up to the 2010 TC 10 Mile, she actually got me to put in the "distance specific" training where I was able to do a 59:05. So... I guess if you train for it like McMillan says... you CAN hit their predictions.

It's just that I so rarely train so specifically for 1 race. I guess that's my problem. :)

Any thoughts on working with a pace calculator?


I Pull 400 Watts 9:46 AM, January 31, 2012  

You are correct. If you use the calculator wrong (like your two friends did), it will produce bad predictions.

Even on the page for the calculator, it mentions that a 5k specific runner will not just go out and run the equivalent time in a marathon.

"The problem with that is that these predictions assume you've trained up for that distance in the same way you trained for the shorter run."

I do not see that as a problem. I do not believe (and would never recommend) using the calculator for a "short" race and predicting a "long" race time.

Like you mentioned, the best way to look at the calculator's times is this. Take a 5k specific runner and give him a year of marathon training. Then he will most likely be able to get pretty close to that predicted time.

Steve Stenzel 10:38 AM, January 31, 2012  

Yep I Pull 400 Watts, I mentioned your 2nd and 3rd paragraph in my post. In bold. And italic.


I Pull 400 Watts 10:47 AM, January 31, 2012  

So the only problem is that people use the calculator incorrectly.

SteveQ 11:23 AM, January 31, 2012  

Of course, there are other calculators.
They all convert 4:53 mile to sub-1:20 1/2-marathon. Can't compare indoor on a rubber surface to windy concrete at freezing temps, at any rate.

Karen 11:30 AM, January 31, 2012  

I've noticed those same things when I use the calculator too. As I never really train specifically for shorter distances, my longer race times (half and full marathon) predict wicked fast 5Ks (by comparison) that I can never hit.

But comparing my 5K time to a 10K is pretty close.

Chad 12:32 PM, January 31, 2012  

I totally agree that you can't just plop in a number, and then expect to hit whatever the calculator spits out - no matter what your training is.

When I called Mike out, I knew he was doing 70 mile weeks. Combine that with his mile speed and it was pretty obvious he could go much faster than 1:28.

I do think that some people are short distance specialist and some are long distance specialists. So that needs to be taken into account when using the calculators.

I think McMillan's calculator and Daniels' VDOT charts are tools that can be effectively used to predict upcoming races based on past races. As you use them more, you'll realize where your performances tend to fall off.

Steve Stenzel 1:33 PM, January 31, 2012  

I Pull 400 Watts: I think that's about what it comes down to. We all enter numbers, but unless the training is radically different to match the specific race, then we can't hit that goal. And (speaking very generally here) I think most people don't really specifically train for 1 race - I think most (me included) just run and fit in some specific race workouts.

Karen: you sound like you have similar "issues" as my wife! She can run those longer races just fine, but then can't quite bust out the speed in the shorter ones. I have the opposite problem! :)

Evan Roberts 2:17 PM, January 31, 2012  

Sometime in December you posted about a half-marathon-esque length training run at just over 1:30 pace. Take away the stroller, put on some racing shoes, and 1:25 seemed pretty realistic.

Also 7 minutes, big difference over a marathon!

Melissa C 4:22 PM, January 31, 2012  

I have used one before, and when I read the run less run faster book, it really says to use the distances that are close to each other to get the most accurate time out of it. Like, the half marathon time is the best predictor of marathon time. It does pretty well w/ my half and full times. My 5K times aren't quite as good.

Meredith 11:10 AM, February 01, 2012  

Mine is all backwards too. I've run a 3:30 marathon, but my fastest half is a 1:38. According to many pace calculators I should be able to run about a 1:30ish half. Too bad it doesn't work that way.

Stacey,  7:03 AM, February 03, 2012  

I didn't learn about the pace calculator until after I'd run a half marathon but when I entered my latest 5k time in, it exactly predicted the half time I had just run. But, on the flip side, it got me into trouble when I was training for a marathon. I went for a time that was too ambitious based on that calculator's predictions (which felt justified since it had magically predicted my half time to a tee) and, of course, ended up being disappointed with my performance.

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