I have decided for sure that one of the pools I swim in is significantly faster in one direction than the other. But I'm trying to figure out if it means anything about the way I swim or if it is entirely on the current of the pool.
My normal pool goes from 4-1/2 feet deep to 10 feet deep. 6 lane, 25yards with roughly 15" of gutter lane on each side. It is kept at a very reasonable 78-80. I love this pool. It feels "fast". I do notice a slight difference in 25's from the shallow end to the deep end of *maybe* 1 tenth. I attribute this difference to being able to get my feet on the wall faster from standing vs from the deep end. I always hit the watch button and then drop and go.
My occasional pool I really only swim at because it's a 5 minute drive vs a 30 minute drive. Useful when you're squeezed on time or just want to do a quick loosen up swim (if the thing is open). It's 84-86 degrees. I usually end up here once a week. It's also 6 lanes, 25 yards but has less gutter lane (about 8" each side). It goes from 3-1/2' on the shallow end to 12' on the deep end. The drop off is noticeably steeper and comes earlier into the shallow end.
In, what I have dubbed the "icky warm pool", I am between .98 and 1.08 seconds slower than expected from the deep end to the shallow end. And anywhere from .7 to 1.2 seconds faster than expected from the shallow end to the deep end. When I look at averages, about .95 seconds faster from slow end to deep end and 1.05 seconds slower from deep end to shallow end. (Supports my shallow end I get the feet on faster theory as well).
Mostly, I've cared in figuring this out because I like to do USRPT sets of 25's so being off by 1 second is more than the difference between going again and sitting one out. At first I thought it was the heat of the warm pool wearing me out quicker but after several abysmal "failed" sets there I stuck out a set of 14 x25 no-fails allowed at approximately 200 pace going again regardless of time to see what happened. This is when I saw a clear pattern of shallow to deep faster than deep to shallow.
These are comparing breaststroke times. But I had also had similarly failed free sets. Does this say sometimething about the way I swim or is this entirely on the pool?
I may have figured out my own mystery.
In the "icky warm pool", from shallow to deep, the pullout occurs in the shallow portion. This is mostly streamlining. So the swimming takes part in the deep end and isn't affected as much by waves. Pretty much the optimum for as fast as possible except that I practically skim the bottom of the pull on the pullout.
From the deep to shallow end I'm mostly streamlining through the optimum part of the pool and when I start swimming, the waves start beating me up from below.
In my happy pool, the shallow end must be deep enough that I don't get as much wave problem but if it was overall deeper, maybe I could swim even faster?
Hmmm...
Hmm. The difference and what might be causing it is interesting. I found this article that may explain.
coachrickswimming.com/.../
The pool I swam in up until a couple of years ago was a very old pool/building (it's now closed). The water return nozzels were all around the shallow end. A couple on the sides, but the other were every-other lane, just below the surface, and pointed directly out into the lane. And the pressure of the water coming out was really strong, and very noticable to swimmers. There was definately a difference in speed between the lanes that had the return nozzels, and those that didn't. Lanes 1 and 6 didn't have the nozzels at the end, but they did have them on the side. In those lanes you would actually notice yourself being pushed toward the center of the pool and into the laneline. But in the article linked above you'll see that pool shape is one factor that will affect swimmer speed.
Dan
Currents from the water circulation can certainly be an issue. There was a mess at FINA Worlds a few years ago when it appeared that some lanes were faster than others.
I believe in most pools that have a shallow end, that it is faster to go from shallow to deep. That way the waves in front and under you dissipate instead of being reflected back at you.
I've noted this in a number of pools in which I swim regardless of depth. For instance one pool in which I swim, if I choose of the lanes in the center (constant depth for whole lane), I have to take an extra stroke in one direction. I do believe it is a water flow issue as the intakes for the circulation system seem to be stronger in those center lanes nearest the pumps.
I used to swim in an outdoor, 50 meter pool with a water slide on the far end. I was always amazed at the effect the forces created by the flowing water would have on swimming times. Our team would practice with the slide turned off obviously, but when we'd have late practices it was on and made the workouts quite interesting.
