Ask the Expert: Field test re-testing in a periodized program
ICA member Sharon recently emailed me with some questions about retesting. Sharon owns a small studio with 9 bikes and has done threshold testing on everyone. They are approaching the first time they will retest, after training with their heart rate zones for three months. Sharon asks:
I am assuming that Sharon did a field test to estimate lactate threshold heart rate (LTHR), and not a threshold functional power test (FTP). However, I am going to answer this question for both scenarios because the answer is slightly different for each one. Today's answer is on heart rate and what you can interpret from subsequent retests. Later I will address how to interpret subsequent testing when using power.
LT Heart Rate
First I want to reiterate a point. A 20-minute or two 8-minute field tests are reasonably reliable means to estimate lactate threshold heart rate (LTHR). I always make sure I remind my students that we are estimating LT, we are not actually measuring it. Lactate Threshold implies that you have measured the lactate itself. This is done with a device that measures actual blood lactate while you are performing a graded exercise test. Metabolic tests are supposedly measuring anaerobic threshold, though some physiologists do not like the term anaerobic threshold because there is no "thing" called an "anaerobic", so how can it have a threshold? Anaerobic is a state, not a "thing" (See? It's even hard to describe!) Ventilatory threshold (VT) is closely associated with LT, though it is a separate physiologic occurrence.
Field tests have been found by exercise physiologists and coaches to correlate very well with the effort level at LTHR. But, there is a definite learning curve when taking field tests. The very first time a rider participates in a field test, there is often trepidation. Questions and doubt pop into their heads, like "will it hurt?" "what if I can't make it the whole way?" "I'm not good enough." "I'm not fit enough."
Once they've experienced their first test, they know what to expect. These tests are never "easy", but some of the fear dissipates. Often after the first test, they realize that they could have gone a little harder.
It's also important to remember the potential variability with heart rate. Heres a reminder of some of the things that may or may not affect one's heart rate on any given field test day:
We try to minimize some of these things by keeping as many conditions the same from test to test, but we (us, as instructors, as well as our students) don't always have control over some of these things. These things may affect one's first test, or the second test or anytime we take a test, so it follows that one is not always 100% sure of how one might have done in the absence of that variable.
In my 12-week periodized programs, I usually schedule three field tests, one at the beginning, one half-way through and one at the end. One of the reasons for that middle test is to minimize the learning curve. Any increase in HR between the first and second tests is not likely to indicate with any kind of certainty that it was due to fitness improvement. It may be, but it also may be entirely due to knowing what to expect and having the mental ability to push longer and harder. That in itself is a benefit, but in the absence of power meters, we really don't have any idea whether they actually improved this metabolic marker or not. What if they were stressed, dehydrated, or fearful the first time around and then just got it better the second time?
When you do your first re-test, before you even start the test, it's important to let your students know what to expect with the results. I always tell them early on that they may not see an improvement in their field tested LTHR estimate, but that does not mean they haven't gained fitness. Here is my typical announcement just before the second field test:
Yes, that's a long speech, but they need to hear it!
So when I do the third field test, I remind them of what I said about not really knowing with 100% certainty whether any increase will be due to an actual improvement in LT. Now that they have gotten over the learning curve and fear, and now that we have been training harder and harder, with longer and longer efforts at (or above) threshold, there is a chance that some of them might see a difference. This is especially true of the ones who were less fit to start - they had a longer way to go with their fitness. Be aware that your long time stronger cyclists may not see a difference in LTHR; it is those riders that would benefit more from the power meters, because it may very well show that their LTHR hasn't increased, but their power at threshold has.
Here is a an example of my speech a few days before my third field test:
So, as you can see, you still cannot promise them that an increase in their HR is due to an increase in LT without the quantifiable proof of power. However, that being said, I trust increases in LTHR after the third test more than I do after the second test simply from the learning curve standpoint. In this way, the second test serves as a way to re-establish a more realistic baseline.
For those who do not see an improvement in the third test, and who seem upset about it, make sure to praise them, empower them, and remind them how much they have worked. Assure them that if they know that they have done the work correctly, then their power at threshold will undoubtedly have improved.
For those who do show an increase in their HR, and you know they have tested at least twice or more prior to that, and you know they have been consistent, and especially if they were starting from a place of low fitness (yes, a lot of qualifiers, I know), then it IS possible that their LT has improved. Improvement can range from 3-8% (a few beats are not statistically significant, remember, it is an average, so there is a margin of error). The higher the improvement, the lower the fitness at which they were likely starting. A more seasoned cyclist, as explained above, is less likely to see a size-able increase in LTHR.
I'll use myself as an example. I've been doing 20-minute field tests like these for a long time. I usually range from 157 - 161. Early in the season I'm closer to 157, and when I am more fit and after a solid training program, I am usually closer to 161. With this history and pattern, I can safely assume that I've increased my LTHR from the 157 to the 161 (~3%). Could I take it higher? Probably not much. The highest number I've ever seen on my HR monitor (about 5 years ago, and I thought I was going to die) is 176, so 161 is approximately 92% of that. There is a physiological limit to how high one can raise LTHR, but with even more focused training (from quitting my jobs and taking up cycling as a career!) I could most definitely significantly increase my power output at that particular threshold heart rate.
Does that make sense?
Let me get back to Sharon's question and her scenario with her group. They have been training for three months and they are about to do their first retest. She doesn't have the benefit of that middle test, which serves as a tool to redetermine a baseline and minimize the effects of the learning curve. On the other hand, they have probably been working harder in these recent weeks, doing workouts designed to improve threshold, such as longer threshold intervals. Therefore, it is possible that their training program would have indeed increased their LT, or at least their power at LT. All of the logic that I've explained above still applies, so be sure to explain to them what an increase in their LTHR may or may not mean.
And then next time you do this program, Sharon (and everyone else) make sure to include three tests (beginning, middle and end) to minimize the effects of that learning curve.Tell me about your field tests. Have you retested yet?