I knew I wanted to do a threshold test to do again today, so I decided to wear my heart rate monitor at a 5K and see if I could engineer a better threshold test. For a typical 5K I run about a 1 mile warmup and then start doing strides, maybe 8-10 of them, running out from the starting line for about 10 seconds at above race pace, walking back, resetting. It's part ritual, part staking out the best line, part warming up.
Some people question 'wasting' that energy. Why would you expend a faster than race pace effort right before a race? I think this comes from a fallacy that you can somehow magically burn 100% of your energy during the 5k- it would be awesome if you could, of course, but it doesn't work that way. It's actually a great way to open up the cardiovascular system and the muscles. It also lets your opponents know you're serious.
Notice the spikes into the 140s from a standing HR below 100. That's a good target for me, 140 peak then a nice drop. Rinse, repeat.
On to the race.
Now, it's hard to tell from the image, but it took me a full three minutes from the start of the race to reach an HR of 160, after which I held above 160 the rest of the race and averaged 162 with a peak of 169. Does that mean I was slacking in the first three minutes? No. I ran my fastest mile, around 5:50, in the first mile. The first mile is always the fastest. I try to get out ahead of comparable athletes and then hold them off. I don't go nuts, but I do start strong and finish on strength, not speed. So that just indicates my heart rate does not immediately spike out- which is good.
Two takeaways from the 5K. I had to attack the warm-up for the threshold test more aggressively. If I was using the gears and achieving the cadence intended and getting only an HR of 120, I needed to push harder and get the same kind of HR I was seeing doing my strides before the 5K. My goal- a much flatter curve on my threshold test.
Well, the curve is a lot flatter. So, is that mission accomplished - did I get a better threshold test ? I'd say the answer is yes. The truth is, I hit the same terminal heart rate in both workouts, indicating that 166-167 upper ceiling is just that. But in the first workout I had to drive myself the entire 20 minutes to reach that level, whereas in the second test, I actually reached a 150+HR in about 4 minutes, similar to the 5K. So it was a better test of my threshold, because of just reaching a terminal HR, I actually maintained that HR for a long period.
But how do I know that's the case? If you look at the short effort after the end of the 20 minute threshold- it's the same workout, and those are three short 20 second sprint efforts- the HR curve is identical.
Lesson: Warm up hard before a TT. But you probably knew that.