With one of my annual goals accomplished so early, I have two options: 1. check it off the list and rest on my laurels for the rest of the year, or 2. adjust the goal and challenge myself to continue improving. As I did in the middle of the race, I choose option 2 here as well. The new goal is < 20:30, shaving off roughly 6 seconds per km. This won't "just happen," though, so following are my thoughts on how to realize this goal.
First I must look back at this race and ponder why I was able to achieve a time a full minute lower than the best time of my recent 5k training runs. There are a few possible explanations: 1. Adrenaline / competition brings about higher performance. This is certainly true, but I don't think it alone can account for a full minute's improvement. 2. Being rested and well nourished / hydrated brings about higher performance. Again true, again inadequate to account for the full improvement. 3. My training runs aren't intense enough. I think this may be the real crux of the issue and it will be addressed in subsequent runs.
Looking forward, I believe the path to my new 5k goal is training each of my energy systems. The human body generally uses three energy systems to do work:
1. The ATP-PC system, which anaerobically uses the ATP stored in cells for quick bursts of high-intensity energy lasting up to 10 seconds. This is the system used when sprinting.
2. The Lactic Acid (fast glycolysis) system, which anaerobically converts glycogen stored in the muscles and liver to glucose, which is broken down into pyruvic acid, which provides slower bursts (up to 60 seconds) of moderate-intensity energy. This is the system used when running 400m.
3. The Aerobic (slow glycolysis and lypolysis) system, which aerobically breaks down glucose (faster) or fat (slower) to provide long durations of low-intensity energy. This is the system used when running distance.
Even though a 5k is pretty high-intensity, my understanding is that you are still using the Aerobic system to produce energy most of the time. By training your Aerobic system, you are able to increase its efficiency and ability to supply energy at higher intensities / speeds. Before I started running, a 4:20 / km pace would probably have "winded" me so quickly that I couldn't have kept it up for even an entire km. This is because my Aerobic system would not have been able to produce energy quickly enough for that speed, forcing my body to rely on the anaerobic systems, which would have depleted quickly. After training, though, I can now sustain a 4:20 pace for at least several km because my Aerobic system has adapted and is able to provide enough energy.
My training thus far has really been focused on building up my Aerobic system. As illustrated above, this goal has been achieved and I will continue to train my Aerobic system with runs of varying pace, incline walks, and other low-intensity activities. Additionally, though, I now need to train up my anaerobic systems.
I believe (although I welcome advice from much more experienced runners / coaches) that the "best" way to run a race, especially races of longer distances, is in three phases:
1. Aerobic: maintain a pace that is supported by the Aerobic system for the vast duration of the race (For long distances, this can include refueling during the race so that the faster glycolysis can be used instead of the slower lipolysis.)
2. Anaerobic 1: pick up the pace for the last 60 seconds, using the Lactic Acid system to get the most out of every last glycogen molecule stored in muscles / liver
3. Anaerobic 2: sprint all out for the final 10 seconds, using the ATP-PC system to get the most out of every last ATP molecule floating around
I don't believe I'm getting enough out of my phases 2 and 3 right now. During a race I am covering 275m in the final 60 seconds. However, when rested I can cover 400m in 60 seconds. During a race I am covering 55m in the final 10 seconds. However, when rested I can cover 90m in 10 seconds.
This discrepancy is significant. Let's say I'm running a 4:20 Aerobic pace. My current final km comes out to 10 seconds (final 55m) + 60 seconds (previous 275m) + 2 minutes 54 seconds (previous 670m @ 4:20 / km) == 4:04. If instead I hit my "potential" numbers described above, my final km would come out to 10 seconds (final 90m) + 60 seconds (previous 400m) + 2 minutes 13 seconds (previous 510m @ 4:20 / km) == 3:23. That shaves 41 seconds off my total time - yowza! I could reach my new goal without changing my pace if only I could hit my "potential" during the "end game" of a race.
I believe I'm failing to run fast enough at the end because 1. I'm still using some Lactic Acid system during the first phase of my run (including the too-fast starts) and 2. My anaerobic systems are just out of shape, having not been trained intentionally in some time. 1 can be addressed with aerobic training and 2 can be addressed with interval training, sprints, and high-intensity workouts. I believe that, if I can address these two issues, I can shave 30+ seconds off my race times without modifying my pace.
Note that this assumes that one can still access the full power of the ATP-PC system after fully depleting the Lactic Acid system. I'm not sure if this is true or not. My experience in this last race seemed to indicate that there was still ATP-PC juice left even as Lactic Acid gas was running out, but perhaps there were other (e.g. psychological) factors at play as well?
I have three 10k races to run over the next six weeks so I intend to test out this training and race running strategy.