High Intensity Low Volume Training

I am really enjoying the transition from typical 40-50 mile running weeks to low milege, high intensity workouts along with biking and swimming. Below is a summary of my running workouts for the week: ................................................................................. Mon: 19 min for 5K following 8.5 mile bike (6:07/ mile).. Tues: 4 x 800 just under 3 min, 60 sec rest (5:58/ mile).. Thurs: 5:42 mile off 12 mile bike........................................ Fri: 11:18 for 2 miles (5:39/ mile)..................................... Sun: 5K in 18:55 (6:06/ mile)........................................... For the week I had ran about 11 miles in 67 minutes (5 runs, 2.2 miles ave for each), just over 6 min mile pace with a handful of solid bike rides and short high intensity swim workouts. All running workouts but the 11:18 2 mile were done on artificial turf, and I wore my trusty Brooks Mach 9 with the insole replaced by a small, thin heel pad.