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Heart Rate Testing Confuses Me

Last updated on December 31, 2020

I’m following the LW Coaching 100 Mile Mountain Bike Race – Finisher Plan again this year, again in hopes that it’ll get me ready to complete the Lumberjack 100 race in June. Part of this involves testing my Lactate Threshold Heart Rate, or basically, my average heart rate over 20 minutes of riding my bike as hard as I can. This average is then run through a formula (one of many — I’m using this one from LW Coaching) to determine heart rate zones. When working out (really, just riding my bike) I then try to stay in the prescribed zone for the listed amount of time, with the idea that this helps build endurance at that zone.

For example, the zones that were calculated for me off of today’s test with an average heart rate (HR) of 170 BPM during the test are as follows:

Zone 1 – Recovery: 111 – 137 BPM
Zone 2 – Aerobic: 138 – 152 BPM
Zone 3 – Tempo: 153 – 159 BPM
Zone 4 – Sub Threshold: 160 – 169 BPM
Zone 5 – Super Threshold: 170 – 180 BPM

Much of the planned riding in preparation for finishing a 100 mile race involves hours of riding in zones 2 or 3, which seems easy at first, but gets difficult as the hours progress. It does seem to work, though, as it helped me get up to riding 8+ hours comfortably, as long as I was capable of pacing myself. Hopefully this’ll continue to help this year, and I won’t quit early like I did last year. I’d really like to finish this race at least once.

Last year I first performed this test on the trainer on the second day of the plan, but ended up with a low-seeming heart rate of 153 BPM. I tried again on April 4th, 2012 and got a result of 166 BPM†, which is what I’ve used for my HR zones for training last year. This current result of 170 BPM has pushed the zones up a bit from last year, and I hope this helps push me a bit more.

Despite using the same route as last year for the test and following a similar warmup I can’t help but question the variances in numbers. Today was much colder than last year (42.3°F vs. 59.7°F), the bike used had slightly knobbier tires and a suspension fork, and there was a lot more wind today. Maybe the harder conditions and higher average HR mean I’ve become a capable of a little bit more over the last year? I’m not really sure.

The more I read about HR zones and LTHR calculation the more confused I become. I was pushing myself as hard as I felt I could go without failing, so with Joe Friel‘s (a pretty well regarded coach) simple adage…

Do not be concerned with anything other than are you going as hard as you can go right now. If the answer is “yes” then you are doing the test right.

…maybe I am doing it right.

† This was then recalculated on May 8th, 2012, but likely due to a loose HRM strap I ended up with a maximum of 225 BPM and an average of 187 BPM, clearly erroneous numbers. As a result I just stuck with the previous number of 166 BPM from April.

Update on May 8, 2013: Yesterday, as prescribed, I performed another LTHR test. Riding the same route (but with a different warmup) in 35°F warmer weather (79°F vs 34°F) my average HR was 2 BPM faster and average speed was 1.5 MPH faster. I think it may have been a bit less windy, which likely explains the higher average speed.

This pushes each of the zones up slightly to the following, which is what I’ll likely use for the remainder of the training plan:

Zone 1 – Recovery: 112 – 138 BPM
Zone 2 – Aerobic: 139 – 154 BPM
Zone 3 – Tempo: 155 – 161 BPM
Zone 4 – Sub Threshold: 162 – 171 BPM
Zone 5 – Super Threshold: 172 – 182 BPM

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