Last night I headed to the Verona High School track to do an ironman marathon time prediction test.
It was a hot, humid night which I was happy about. Not because I like the humidity, but because this test is a heart rate based test and I knew the heat and humidity would raise my heart rate and affect the test. That may sound like a negative thing, but I was thinking that if I could hit the numbers I wanted on a hot, humid night, I'm set. Plus, I think the increased heart rate from the heat more simulates the ironman because you run the marathon in the afternoon and you're already fatigued from the bike so your heart rate is going to be higher for a specific pace than it would be if you were fresh.
The first thing you need to do is set your heart rate zone. There are two ways to do this. The first way is to take your lactate threshold heart rate (your 5k heart rate) and multiply it by 82% and 88% to get your zone. Doing that gives me 145 bpm for the bottom of the zone and 155 bpm for the top of the zone (my 5k heart rate is 177 bpm).
The other way is to subtract your age from 180. That's the bottom of the zone. Add 10 beats and that's the top of the zone (I believe this comes from Phil Maffetone, not positive). I'm 35 so 180-35 = 145. Add 10 and I have a zone of 145-155. Interesting that both ways came up with the exact same zone.
The workout starts with a warm up. Then you run until you get your heart rate up to the bottom of your zone. I find that it helps to do a full lap at that heart rate before beginning the test. Otherwise your pace is off for that first lap.
Then you run 6 laps at that heart rate - 145 bpm for me - and you record each split. Here are mine:
Then you get your heart rate up to the top of your zone - 155 bpm for me - and run 6 laps at that heart rate and record your splits.
Then do a cool down and you're done.
What you do is take the numbers from your first set and figure out what your average pace was. I ran the whole set in 11:54 which is a 7:56 pace.
Then take the second set and do the same. I ran that in 11:11 which is a 7:27 pace.
Then add 30 seconds to your second set pace. That puts my second set at a 7:57 pace. Then you take the two paces and average them together and that's your ironman marathon goal pace.
I've been targeting an 8 minute pace for this whole year of training so coming up with a 7:57 pace on a hot, humid night for this test is very reassuring. Of course, it's just a test and you have to compare it to other workouts to see if it's realistic because there are a lot of variables that can affect your ironman marathon. But I've felt like my workouts lately have been indicating my 8 minute pace goal isn't out of line so this test gives me confidence.
A general rule of thumb is that successful ironman athletes can hold a heart rate approximately 20 beats below their threshold. That would mean I could hold 157 bpm, and I'm hoping to keep my heart rate below 150 on the run...definitely below 155. I did a 21.5 mile run on Sunday at a 7:40 pace and had an average heart rate of 137. That was in cool weather in the morning, but I think that run and this test shows that I'm on target.