Well, had to happen sooner or later. Seems I've run full-speed into a plateau with my intervals. The last two times I've attempted my new interval workout, I've gotten stitches and had to modify the workout (either by decreasing intensity, or increasing recovery time, or both) to finish. I hate stitches!
Inspired by "Six Sessions of Sprint Interval Training Increases Muscle Oxidative Potential and Cycle Endurance Capacity in Humans", I've decided that instead of trying to stubbornly push through the same workout until I complete it (which will be both frustrating and potentially demoralizing), I'm going to switch it up. I've realized that my "sprints" in my intervals are not sprints at all. The reason I reach "failure" in my interval workouts is because I have extremely short recovery times (about 45 sec), and my recoveries are still at a reasonable pace (5 - 5.5 mph). So, for the next two weeks, I'm doing faster sprints with longer recoveries. I wish I could get out on a track, but I'll see if I can accomplish this on a treadmill, and may even throw in some cycling sprints for good measure. Then, three weeks from now, I'll attempt the same workout from today that I died during. According to the paper, I'll be good to go.
Stay tuned. =)