Spacegal flies down to earth.......!
Every athlete I've ever coached has worked on a very basic AT (anaerobic threshold session) in each discipline; the dreaded 6 x 6 minutes!
For swimming, we'd look to go 6 x 400m with a minute recovery, for running 6 x 1 mile, and for cycling, get the turbo out and work that 6 x 6 minutes. Pace is race pace plus a little bit, recovery is restricted to just that one minute (as we tend to get no recovery after each mile in racing etc.... do we....)
OK, having written that down, don't feel that you go out and push straight into that session. depending on your fitness, you might want to go, say, 4 x 4 minutes to begin with and work up.......... Hope that makes sense, come right back to me if it doesn't.
steve t