Livin' in TRIMP Tower
Amongst cyclists, there are mixed opinions about Strava, the social network that promotes tracking, analysis, and sharing the GPS logs of one’s rides.
There’s no question of the value it provides. But there’s been a bit of backlash from non-competitive riders who think preoccupation with “the numbers” detracts from the pleasure of riding. While that might be how it is for them, that doesn’t confer upon them the right to judge others for whom Strava’s information actually enhances their cycling experience.
Like many sites, Strava gives free users access to most of their functionality, but saves some advanced features for paying members. For myself, the ability to create my own heatmaps wasn’t sufficient reason to pay for access. However, a recent offer of a free month of premium access finally lured me in.
Although it’s not the main point of this post, the first thing I had to look at was those heatmap charts. A year and a half ago, I put together my own heatmap of a year’s worth of my cycling in Boston, which you can see here.
In comparison, here’s Strava’s heatmap of all the 500+ rides I’ve logged since 2010. Click here or on the image to get through to the interactive map where you can pan and zoom around.
They also let you generate heatmaps for a particular calendar year or an arbitrary date range. So here’s another chart showing where I’ve ridden since moving to Pittsburgh back in December. Click thru for the interactive version.
Clearly they’re more flexible and less work than creating my own from scratch.
Another premium feature worth a brief mention is the “trophy case”. Strava offers monthly climbing or mileage “challenges” to all riders, but when a paying member completes a challenge, Strava adds little badges on the “trophy case” section of their rider profile page.
Since those aren’t shown for free users, I never paid much attention to the challenges I’d completed, but now they all show up on my rider profile. In 2014 I completed four monthly “gran fondo” challenges plus one long “summer challenge”. In 2015 I added three more gran fondos. And thanks to favorable weather, I’ve already completed two more this year, and will complete my first monthly “climbing challenge” in a couple days.
That’s all nice, but it’s not the premium feature that I really want to show you. The main point of this post is the “Freshness & Fitness” chart, which I want to explain in some detail, because it’s cool.
For visual reference, here’s my fitness chart for the past 12 months. Click the image to see it at full size.
Look first at the histogram across the bottom. Each one of the vertical lines represents a ride. Each line’s height represents the ride’s difficulty, based on its intensity and duration, and is called its “training impulse” or TRIMP or “suffer score”. The harder the ride, the taller the line. Above, I’ve highlighted last September’s late-season Hub on Wheels ride; it was a very intense three-hour ride, which is reflected in its training impulse value of 315.
Now look at the main/shaded/dark/bold line on the line chart above. That’s a different measurement called “fitness”, which represents my overall strength on the bike. You’ll see that every time I do a ride, my fitness goes up in proportion to how hard the ride was. So when I ride, I get stronger, but it gradually declines on days that I don’t ride.
There’s a spike at the Hub on Wheels ride where my fitness jumped up from 26 to 33, then slowly declined to 22 over the next three weeks while I was off the bike. Similarly, I was at peak fitness in June after riding hard and often, but my overall fitness declined through July and August, when I rode considerably less. Technically speaking, fitness is a weighted average of the training impulse for the previous six weeks.
There’s another metric that I haven’t shown here in order to keep the chart clean. We all know that after a hard ride, it can take a couple days of rest for your body to recover before you can go hard again. To take that into account, there’s another metric called “fatigue”.
Like fitness, fatigue increases in proportion to how hard you rode. After Hub on Wheels, my fatigue rose from 6 to 47. But it takes only a few days to recover from fatigue; a week after the Hub ride, my fatigue had gone back down to 17. In technical terms, it’s a weighted average of only the past 7 days’ training. While the positive effects on fitness of training last a long time, the negative impact of fatigue does not. That’s fatigue.
If you’re training to get ready for a big event, both fitness and fatigue matter. You want to have trained hard and built up your fitness, but if you’re still suffering from fatigue, you’re not going to perform at your best. If you take your level of fitness and subtract your residual fatigue, you get a number which they call “form”. Form is the thing that really matters when it comes to predicting how you’ll perform on any given day. And that’s what the thin/light/grey line on the chart represents.
Looking at that light grey line on my chart, during my heavy training period in the spring and early summer my fitness rose to its peak, but my form never got especially good because I was so fatigued. But I rode a lot less after my major event at the end of June, which allowed my body to fully recover. Looking at the chart, my form didn’t actually peak until late July! Going into Hub on Wheels, my form was a moderately good +20; after riding so hard, it fell to -14; but after a week of recovery it was back up to +11.
Stepping back, that chart gives a good overall picture of how a cyclist’s year progresses. You start with low fitness over the winter. In the spring you gain fitness by doing hard, long rides, but those leave you really fatigued, so you’re not at your best until you’ve taken the time to recover. That’s why you have to taper your training in the week leading up to a major event, so that you’ll be fresh (less fatigued) and thus at peak form. And then in the fall you can finally enjoy being highly fit without having to train hard or endure the associated fatigue.
In addition to 6- and 12-month views, Strava will also display all of your historical data, which for me goes back five years to 2011. That’s shown in the chart below, which only contains my overall fitness, with the expected troughs in the winter and peaks in the summer. Again, click for bigness.
There are some really interesting things to see here, too.
What immediately jumps out at me is that each year’s peak fitness was greater than the previous summer. New cyclists experience this year over year improvement as their body responds to the training load and becomes ever more attuned to cycling. You don’t just get fitter from winter to summer, but you also improve from year to year. Although I wouldn’t have expected to see that trend continue for someone who has been riding for 16 years, apparently I trained harder each year from 2011 to 2015, as shown by my peak fitness values, which went from 44 to 57, 62, 74, and 73.
The wintertime troughs are also interesting. The winter of 2011-2012 I barely rode at all, which is why you see a smooth decline in my fitness (down to a sad little value of 1). Skipping ahead, in 2014’s off-season I tried to ride outside sporadically, which is why you see some big jaggies there. But the most interesting years are 2013 and 2015, when I regularly used the indoor trainer. Riding the trainer produced numerous short little saw-toothed increases in fitness, which added up to provide a good base of fitness and a head start going into the arduous spring training season.
And finally there’s this past off-season. You don’t see any evidence of indoor trainer last winter, but Pittsburgh provided enough nice weather to ride outside regularly, and enough obscenely-difficult hills to really amp up the “training impulse”. So much so that according to this methodology, I’m as trained-up and fit now (in March) as I normally would be in the latter half of May!
Being two months ahead of my usual training curve is probably a good thing, knowing how much more climbing there is in the average Pittsburgh ride than back in Boston.
These are only a few of the features that Strava offers to premium users. For you, they may or may not be worth the expense; it took me five years to even look into it seriously for myself. But I thought I’d share some of the insights that you can gain.
Of course, you can get this kind of information (and more) from other performance management software such as TrainingPeaks, but getting it as a part of Strava Premium is pretty convenient for me. And Strava provides a social network that makes it easy to share with other riders and anyone who reads this blog.
And while we’re here, if you like this kind of stuff, don’t forget to install the Stravistix Chrome browser add-on, for additional analysis of your Strava datums!