Pool-running for the non-injured - pluses and minuses

So, with my first race this past weekend, I consider myself to have graduated from "recovering injured runner" to "out of practice/trying to improve runner."

*knock on wood*

I'm still doing a lot of pool-running, though.  Whereas before I trained off of fairly high mileage (70-90 MPW), now I'm only at 30 miles per week on land, with the balance of my mileage in the water.  And I never would have believed it before, but it seems to be working.

I have noted many benefits to using pool-running as a cross-training for the non-injured runner.  So, what the heck, why not list them here (along with some minuses).

• Post-race recovery. The biggest benefit that I've noted has been in my recovery from workouts.  It's really amazing, but an easy pool-run of at least 30 minutes seems to work better for post-workout/race recovery than anything else I've ever tried (including massage, ice bath, shake-out run, or any of the above together).   I think it's due to the combination of a) the coolness of the water; b) the pressure of the water forcing circulation; and c) the gentle active stretching that comes from moving your legs through their full range of motion in the water.
  It's really uncanny.  I've found that it works well for weight-training as well -- I can do a heavy weight-training session, and eliminate almost all muscle soreness by hopping in the pool within a few hours post-weights.  And easy pool-running sessions immediately after a track workout mean fresh legs the next morning.  It's absolutely amazing, and I don't say that often.
  
• Recovery "runs".   One of the tried and true tenets of competitive running is to keep your hard days hard, and your easy days easy.  Put another way, your workouts are your prime focus, and everything else is recovery from those.  Extra mileage helps, but only if it doesn't detract from your workouts.
  Thing is, when running those extra miles, it's hard to keep them slow enough to truly recover.  Sometimes it's ego -- you don't want to log actually running as slow as your body needs; other times it's that you're in a hurry, and trying to fit in x number of miles and still finish in time to prep for a conference call.
  Pool-running makes it very easy to keep your easy days easy.  There's no pace to log, so you feel more free to lower the intensity to what feels right.  And since you do pool-running by time rather than distance, there's really no way to hurry it up, and so no urge to push the pace.
  Though I can honestly say I've always tried to keep my easy days easy, it's a lot easier to do so when subbing pool-running for land.
  
• Injury avoidance.  Obviously, subbing pool-running for recovery runs reduces your chances of aggravating a nascent injury incurred during your previous workout.  But, there's another, more subtle benefit.  The more you pool-run and begin to trust that it works, the more willing you become to hop into the pool at the first sign of injury, rather than toughing out runs so that you don't get behind in your training.  And that's very good for reducing the risk of setbacks.
  
• Increased volume.  Due to the lack of impact, you can also sustain a much higher workload in the pool than you can on land.  This is crucial for people like me, who a) benefit from a high volume of low intensity work, but b) don't seem to be able to handle the impact associated with that volume.  If I could build up to and handle 100MPW without injury, I think that would be best for me.  But I don't believe I can (based on past experience) and the pool-running works wonderfully as a second best option.
  
• Appreciation of what you have.  Once you've spent a ton of time stuck in the pool, every run outside seems like a gift, not a chore.   I've never found it so easy to step out of the door in 20 degree weather or harsh winds.  Track workouts are treats, especially since pool-running workouts, if done correctly, hurt worse and for longer than anything you do on land.
  And, you really can't justify skipping a run due to rain when your alternative is pool-running.  You're going to be just as soaked either way!
  
• Non-running benefits.  Get a waterproof iPod or similar, and the hours of pool-running give you an opportunity to catch up on your favorite podcasts (I choose not to run outside with an iPod due to safety concerns, so I can't use long solo runs this way).  
  Benefit #2 is the substantial reduction in shoe expenses that accompanies the reduction in land mileage (though this may be countered by the need to purchase new bathing suits, plus pool fees).  
  There's also a cosmetic benefit.  I've suffered from bad acne nearly my entire life, and this is the first time that my facial skin has been consistently, beautifully clear.  The fact that I no longer need my Retin-A is huge (and a cost saving that more than offsets any new bathing suit).

There are, of course, a few minuses.

• Tedium.  Yes, you're running more or less in place.  Yes, you're seeing the same walls for hours.  There are a few ways to address this though, and it also gets easier the more you do it.
  
• Lack of mental toughness.  While pool-running workouts do hurt MORE than land-running workouts, they also hurt in a slightly different way.  Your lungs burn more on land even with the lowered effort, and the legs hurt differently.  Your first tempo or track workout or race will be an unaccustomed shock, and you need to be prepared for that.
  
• Lack of physical toughness.  Running is a high-impact sport, and there's no getting around that.   Pool-running does nothing to prepare your bones and tendons for handling impact, and the difference is miserably clear when you first return to land-running.  As a corollary, pool-running clearly does very little to encourage bone-strengthening, since it is non-impact -- this is a concern to those of us with bone density issues.
  I also can tell my lack of land-mileage at the end of tempos and races -- when I fatigue, my legs lose their strength and my form disintegrates much quicker than before, when I held a much higher mileage.  I suspect that long progressive runs are key to addressing this.
  
• Pacing.   Quite simply, my ability to accurate gauge my pace when running (which I used to be so proud of) has gone to heck.  I attribute this to several things:
• When you're running in place, your inner GPS atrophies. You never have the opportunity to practice pacing when pool-running, and so you lose your feel for how effort translates to distance travelled. 
• Using pool-running for your recovery means that your legs are deceptively fresh for your running days.  In past days my legs were continually tired from high mileage, and thus functioned as a natural regulator.  Now, my legs feel bouncy and zippy, and continually tempt me.
• As mentioned above, pool-running workouts are done at a much harder effort than land, in order to get the same benefit.  When one first returns to track workouts, it's very hard to remember to tone back the effort level appropriately.  Thus, you go out too hard, trying to hit a level of effort that is no longer necessary.

On the whole, I have to say that the benefits outweigh the minuses, which can be compensated for.  It's a huge tool to use in one's training, and I view my discovery of the benefits of pool-running for a competitive runner to have been part of the silver-lining to my broken foot.