At first, when I was doing "baby runs" of 30 seconds to 5 minutes, I essentially just tacked on the baby run to the front end of my pool-run. As my land-running volume slowly increased, I would cut back the pool-running some, to keep the same volume, but still do both together in a single session. First land-running, then pool-running, with the proportion of land-running gradually increasing over time (I'd start and end my run at the pool entrance, having left my stuff in the lockerroom before hand).
I kept doing this when I first started hitting the track. On my very first tempo workout, which was scheduled to be 2-3x3200m, I did the first 2 mile interval on the track, then hopped in the pool to crank out the equivalent of the other two. And even after I was up to full workouts on the track, in the name of caution I would skip the cool-down jog on land, and instead do it in the pool.
I've since gotten back to doing full track workouts, including cool-down jog. However, I've kept the habit of hopping in the pool for some pool-running immediately after (it helps that my pool and the track are immediately adjacent to each other). 20 minutes of easy pool-running functions very much like an ice bath -- the cold water plus the pressure plus working my legs through their range of motion does wonderful things for recovery.
Of course, combining land-running and pool-running in one session does require a bit of planning. Here's some tips:
- What to wear? Actually, this isn't as obvious as it first sounds. As a woman, in cold temperatures I found that I was actually able to run in my bathing suit, covered with running jacket and running tights, with no chafing issues for runs of up to an hour (and I chafe at almost everything). The two drawbacks were a) the obvious panty line (which didn't bug me at all) and b) the fact that my bathing suit generated a great deal of static and interfered with my heart rate monitor. One plus was that it can be very hard to put on a bathing suit with hands cold from being outside -- wearing the suit under evaded this issue.
I wouldn't try this in the summer, though. Bathing suits aren't really designed to handle large amounts of sweat, and it would seem to me that you would drastically shorten their lifespan by exposing them to that. In the summer, I wear normal running clothes, and then change.
I have not tried running in a tri suit, though I imagine that might work wonderfully (I haven't because they're damn expensive and silly looking to boot).
- Which one first? IMHO, it's better to run first, then pool-run. For one thing, if you're returning from an injury or are injury prone, then you need to be taking every precaution to avoid reinjury. My practice is always to do the activity that is riskiest when I'm fresh, since tired muscles are more likely to lead to form breakdown and increased risk of injury. Thus, running (higher risk) always precedes pool-running (lower risk). Furthermore, in the winter, running post pool-run means that you're outside with damp hair -- not good. And in the summer, it's incredibly refreshing to hop in the pool after a hot run outside.
- Showering? Let's be honest, though all pools have signs requiring that you shower before entry, how many of us actually comply? I'll confess that I do NOT shower when I'm hitting the pool first thing in the morning, or after a day of inactivity. And heck, if I've just come from a short run in cool temperatures, I don't generally shower either. However, my rule is that if I've broken a sweat, or alternately have dirt encrusted on me (i.e. from running on the towpath), then I shower pre-entry. To skip the shower is unfair to the other people in the pool.
- Pre-planning. It's pretty obvious that you wear your running clothes, and bring a bathing suit and a towel. What is less obvious, until you've done this once or twice, is that you also want to bring a second change of clothes, including clean socks and even shoes. It's one thing to drive home in sweaty running clothes post-run, and quite another to have to get out of the pool and change BACK into those sweaty running clothes.