10k times faster than 2 x 5k PB?

[jsmoke]

As I've never run a 10k it's hard to say but I do see more often than not 10k times which are around the same as or faster than twice the person 5k PB. Is there a good reason for this. Maybe they don't run 5k's much for example.

Say somebody had a 5k PB of 19.50 and a 10k PB of 39.20 sort of thing. Your basically running twice your 5k PB.

 

[ci_newman]

Personally I just don't run 5K. I race long distances and in long distance races I'm still warming up at 5K.

Generally speaking I also run for fitness, and a 5K (regardless of speed) just isn't much of a workout. I need longer distances

 

[McBain]

I find the first couple of KM the hardest, once I'm in the swing I run considerably smoother and faster. Pretty sure I'd have a quicker 10K than two separate 5Ks, not that I could prove it I don't tend to run less than 10K.

 

[D.P.]

I have never run a 5k and have no desire ever to, like ci_newman, 5Km is barely a warmup.


From a strictly physiological point of view, it is impossible to have a 10km time faster than 2x 5km if each race is pushed to their limits. Not least, it is perfectly valid to use any 5km timed stretch as your 5km PR, even if that came within a 10km, or even a full marathon.

 

[D.P.]

I find the first couple of KM the hardest, once I'm in the swing I run considerably smoother and faster. Pretty sure I'd have a quicker 10K than two separate 5Ks, not that I could prove it I don't tend to run less than 10K.

Nothing stops you doing the warmup before a 5km though, so that in itself shouldn't be a problem. 10km is the shortest I have raced, and I did 3.5 miles of warm up before hand and then another 3-4 afterwards. Even for my most recent HM I did around 2.5 miles warmup. It is only with a Marathon and above does a warmup become a really bad idea because you simply don;t have the the glycogen to spare, and muscle fatigue is critical. Shoter distances are dominated by aerobic capacity and running efficiency.

 

[neilw]

You can use the calculator here to work out predicted times based on other times.

https://www.mcmillanrunning.com/

 

[semi-pro waster]

As I've never run a 10k it's hard to say but I do see more often than not 10k times which are around the same as or faster than twice the person 5k PB. Is there a good reason for this. Maybe they don't run 5k's much for example.

Say somebody had a 5k PB of 19.50 and a 10k PB of 39.20 sort of thing. Your basically running twice your 5k PB.

Your suspicion that those sort of time differentials are because they don't run 5kms often is probably right, as D.P. says if you/they are pushing to the limits for each run then the 5km should be less than half the 10km time. There are other considerations including whether the 10km course is easier/flatter, whether the runner was more experienced/had a better base level of fitness when setting the 10km time, whether they had a poor build-up to the 5km run (e.g. illness, lack of training) or whether the runner had done more specific training for the 10km - there may be others but that's a few reasons why you might have an anomalous result like that.