Saturday, August 20, 2016

How to tell if your base training is working.

All you need is a GPS watch (or a stop watch & a course whose distance you know) and a heart rate monitor that records data!

I think most of us would agree that endurance athletes tend to have a certain temperament, part of which is the ability to make a long-term commitment to consistently do incremental, sometimes-boring, not-necessarily-gratifying work on a day-to-day basis without much in the way of immediate feedback. Like, if you're the type of person who needs to see progress on a daily or even weekly basis, you probably won't find endurance sports very satisfying.

For the most part, I do okay with the day-to-day grunt work. I'm mostly fine with delaying gratification, but it is still nice to see some evidence that the work you're doing is accomplishing something. I get this urge even more when I'm doing nothing but slow, easy runs, I suppose because it can get soooo monotonous.

Anyway, if you come here often, you probably know that this summer has been a VERITABLE THREE-RING CIRCUS of aerobic base training up in here. Garmins! Heart rate monitors! Maaaaaaaybe breaking marathon pace + 1:30 going downhill with a tailwind!

Settle down, y'all.

I'm not going to completely rehash the whole "Why aerobic base training?" schpiel here, but you can check out the following posts if you want to read more.

Because numbers are my favorite (also because I enjoy a little validation as much as the next gal), I've been collecting data on my runs this summer & putting it all into a nifty little Excel table, plotting the date on the x-axis and my running economy (or, really, a decent proxy thereof) on the y-axis. (Units = miles per heart beat. Technically speaking running economy is about oxygen consumption, but heart rate is a pretty good indicator of that and is much easier to measure directly.)

So, after 9 weeks, what have we got?

(See this post for information on my methodology/math.)

Not bad, eh?

As you can see, the data jumps around a lot from day to day and even week to week because there are so many factors that can affect your pace & heart rate on a given day (weather, sleep, stress, medications, general fatigue, GPS issues, HRM accuracy, etc.). Because of this, you need rather a lot of data points before you can see the trend clearly.

BUT, after 9 weeks, there is a clear trend. We can have Excel calculate & plot the line of best fit (which you can see running through the data points.) Much, much cooler, though, is the fact that we can also have it calculate the variance (the number labeled R2). What is variance? Basically, it tells you what percent of the trend the x variable is responsible for. In the data above, R2 ≈ .33, which tells us that the x value (the date, ie, how many days of base training I've done) is responsible for about 33% of the variation. That means all those other things (weather/sleep/stress/GPS/HRM accuracy/etc.) account for about 67% of it.

Essentially, this is telling us that about a third of how efficiently I've run on any given day has been a result of how far into the training I am (and also that there is a lot of noise caused by other factors--weather, device accuracy, sleep, stress levels, etc.).

Now, we can't automatically assume all of that 33% is due to base training, because there are some other things connected to the passage of time besides how much base training I've done. For example, how many days of strength training I've done, or the fact that I have gradually been losing a little weight these last few weeks as my mileage has picked back up. If I wanted to be SUPER rigorous I'd have to control for all those things (which is a little impractical if you're just a normal person training to do your best at a race).

Obviously I expect to still continue getting faster as I add in speed & tempo work due to improving my VO2 max & lactate threshold, but I am curious to keep tracking this data for my easy runs to see if my running economy continues to improve between now & CIM, or if it levels off.

Want to track your own running economy (or proxy thereof)? I have a spreadsheet with all the formulas already set up which I'm happy to share with anyone who's interested. Just let me know.