How accurate is max speed/pace during runs?

I've had no problems at all with the GPS on my watch. Never had any unusual speed spike or anything.

Today during a walk, I decided (for the first time, I think in my entire life) to do a couple all-out sprints. Running as fast as I possibly could for short distances... just to see what would happen. Each sprint was quite short, 80 meters or so. But my max speed on each one was INSANE. Like, nowhere near where I would think it should be as a not-very-athletic guy.

I mean, I felt like I was running pretty darn fast... but not like, breaking any records or anything. I literally haven't sprinted in 20+ years.

The watch registered a peak 23.1mph (2:36min/mi pace) on my fastest sprint. The other sprints weren't far behind that. Am I seriously that fast, or is the watch over-shooting reality by quite a bit? Other people's experiences with this are welcomed... at that speed I'm genuinely curious if I'm actually capable of sprints like that. Going to a measured track soon to see if my 100m timeactually substantiates my watch's claims, but curious what others think in the meantime.

Here's the activity: https://connect.garmin.com/modern/activity/4928531203

FYI, I'm definitely NOT a pro runner. I can barely run a 5k without stopping to rest. That said... it really did feel like I was hauling @ss The run in the middle where I hit 2:36min/mi was the one where I definitely ran the fastest, I felt like I was going to pass out after about 5 seconds

0 Former Member over 5 years ago

I was doing some flat-out 80-100 m sprints on a stadium track a while ago (clear skies, no tall buildings around). The best pace registered by the watch was 1:43 min/km which, I believe, translates to ~ 2:45 min/mi. I was skeptical back then and I still am. I might try again at some point. And I am not a running type either. Anyway, you beat me, good job!

0 subra over 5 years ago

I mostly ignore max values, except max HR with using HRM chest belt.

If I look in my reports>progress summary in GC there are several running speeds above 20km/h, that I never have run. My peak running speed is 113,8km/h (pace=32s/km). With this I outdistance Usain Bolt.

0 morey000 over 5 years ago

the watch generates a GPS location once per second. Each point is only accurate to 10m or so. The watch's algorithm tries to smooth out the points and predict an actual position and velocity. The instantaneous pace display is averaged over about 10 seconds for stability and accuracy.

bottom line- yeah, don't believe it if it doesn't seem to be true. I was doing 100m repeats today, and I think they were fairly consistent, but some came out quite a few seconds different for each one. The average pace over a distance is pretty accurate. But for short periods- I doubt it.