Friday, May 09, 2014

Tactics - Strava Playback

So the other day on bike forums someone mentioned that Strava lets you playback rides and such. I saw something about this but it didn't seem relevant to me. Meaning I almost never ride with anyone else and the majority of my training rides are indoors on a trainer, so Strava is more a public training diary than anything else.

Then someone said that he "watched" the playback of a race and saw someone stop for a lap and then jump back in, saying it was sort of funny to see it right there in "real life" if you will.

This made the "playback" feature seem a bit more interesting to me because I'm always curious about analyzing race tactics after the fact. Rehashing a race fascinates me because I have some solid data, like my power and heart rate numbers, my "perceived effort" memories, and a better understanding of what was happening around me.

I went to look for the "playback" feature on my Strava pages but couldn't find anything. Google rescued me - it's not really a "feature" yet, it's sort of in testing.

So this is how you do it.

First you need to go the Strava Laboratory.

The Strava Labs screen.

From there click on Activity Playback. This brings you to the Flyby Page.

The Flyby page, with a box up at the top right for putting in a URL.

Based on the name and the notes it seems that Strava put this in place so that if someone rides by you ("fly by") you can look for your activity and any Strava riders near you. I suppose that you could use this to learn about and follow a local rider, see if the rider that blew by you turned off and stopped, stuff like that.

For me, though, since no one rides past me while I'm on the trainer, my interest sits in recreating a race.

To look up an activity you need to go to one of your activities and copy the URL.

For my sake I'm going to use the last Bethel, the Zwiedzanie Bethel. The URL for my activity is

Copy/paste the URL/address from your actual activity.

I copy/paste that into the activity field in the Flyby Page.

My activity copy pasted into the Flyby box.

This brings up my activity plus a list of riders that were at the same location that day. Each name has three columns. The first is the green "C", for correlation. The higher this number the more likely the rider actually rode with you. For a race if the C is too low then the rider probably did a different category race. As a rule I find that anything over 50% is pretty good, it means they usually rode with me.

The second column is the purple "S", for spatial. This means the rider rode the same roads as you did. Obviously if they did a crit on the same course then the S will be high. I ignore this for race reviews since everyone does the same course, at least the ones I race.

The third column is the red "D", for distance. This just tells you how far the particular person rode. This is a sanity check since some riders will do a couple races or warm up for an hour or get shelled in a few minutes. I tend to ignore this also, but I think it would make sense if you were, say, checking to make sure riders completed a required loop (like in a road race, time trial, or gran fondo). It would help catch out those that sit out a few laps or do a shortcut.

Finally you can hover over each name to get the title of their ride. For the Bethel race I did the Cat 3-4 race so anything with some reference to that gets picked. Those that say M45 or P123 etc get skipped.

For me, then, I check off all the riders whose C value is over 50%, seeing if their activity title matches the Cat 3-4 race. A lot of people put non descriptive titles so it's hard to tell (like "Bethel race"). Obviously I recognize a few names so I make sure to get them checked off.

Then I hit play and see if it makes sense.

Each rider shows up with their avatar/picture in a circle. If you selected one that wasn't racing (or whatever) you can hover over the circle, get their name, and uncheck them from the list.

So during the race you can see things develop.

It also plays in fast forward so it's not an agonizingly slow thing. In fact you need to use the arrow buttons next to the play button to advance a frame at a time, else it's virtually impossible to watch detailed bits of playback.

Tip: the elapsed time seems to adjust automatically so you can sort of ignore it. For example I turn on Strava on my phone pretty early so that it's on when I go to the line. After I turned on Strava I took some podium pictures and such so there's a lot of time where I'm not moving at all, hence the weird time at the start of the race.

Start of the race.

If you do the same event as my example you'll see everyone lined up and waiting as I take some podium pictures. I hustle to the line and we start immediately.

The break develops.

In this particular race a massive break of 14 riders went clear. Since not everyone has Strava it's not clear but it would be cool to see a fully-Strava-equiped field in replay mode.

Field sprint at end of race.

In the field sprint we come close to catching those off the back of the break. I'm leading the charge up the hill and there are some break guys that are already at their cars. Others are blowing up at the line and barely moving.

So that's my short tutorial on Strava Flyby, the playback feature available on Strava.

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