Doing The Pacing Math For The 1650

Earlier today I posted an email I got from a swimmer who is trying to figure out a pace for swimming the 1650.  Here is the background (you can read the full post HERE) -

This swimmer was able to swim the following:

- 1,000 at a 1:30-1:32 pace
- 8x 100 with about :20 rest at about 1:25 pace
- a 600 a little under 1:30 pace

The swimmer wants to know what would be his/her 1650 pace based on those swims and do I think that they could swim 12 x 100 at sub 1:25 with :20 seconds rest.  So the answer to the second question of being able to swim 12x100's on 1:25 pace with 20 seconds rest I say yet.  If you can do 8 of them 4 more isn't that much.  I will admit that I get fatigued in a different fashion than most as for example if you use the three examples given I'd have to guess taht my 1,000 would be at a faster pace then what I'd swim 8x100's.  For whatever reason when I swim once I get into a tempo I just keep at it but when you break it up by 100's I slowly fall apart as my body just can't to get back to a tempo. 

As for the 1650 I'd take you 1,000 divide it by 2 to get your average 500 split.  Which would at a 1:32 pace you'd do a 1,000 in about 15:32.  So take 15:32 and divide it by 2 which would be 7:46.  Then take 7:46 and add it to the 15:32 for your 1500 which would be 23.18.  Then add in another 150.  Or you just use a pace calculator to figure it out.  Using one calculator I found online you 1650 time at a 1:32 pace should be 25:18.  I'm basing this all on looking at other swimmers splits online.  Most poeple's last 650 is the fastest part while the 1st 500 is the second fasted part.  Something about the middle 500 trips most of us up.  Mentally I think we all try to save something up and pull back too much.  Since the swimmer said he/she swam the 1,000 on a very manageable 1:30-1:32 pace then I'd guess a 1:32 for a 1650 is doable.  It won't be very manageable but swimming the 1500/1650 is never "very manageable", at least not for me.