I stumbled across this really interesting Masters Thesis paper called “ASSESSMENT OF VENTILATORY THRESHOLDS FROM HEART RATE VARIABILITY IN FIVE INCREMENTAL TREADMILL TESTS IN CROSS
COUNTRY SKIERS” by Ibai Mendia Iztueta. Link to the pdf is here: https://jyx.jyu.fi/dspace/bitstream/handle/123456789/44123/URN%3aNBN%3afi%3ajyu-201408272673.pdf?sequence=1
The short version is this: using RMSSD or STDNN (the normal time domain metrics used for tracking heart rate variability or HRV) and LF/HF (normal frequency domain metrics used for tracking heart rate variability) while doing a graded (step) treadmill test can be used to approximate the location of VT1 and VT2 in XC skiers.
For finding VT1 or AeT, as workload increases during test, the RMSSD or STDNN metrics drop linearly until a point where they stop dropping and either remain the same or start creeping back up slowly. Check out the plots on the screenshot that I attached. The point of this dramatic slope change coincides with the VT1 marker as confirmed in the laboratory test.
For finding VT2, the process is a bit more involved and uses the frequency domain metrics. I didn’t read much on this one, since I am personally more concerned with finding VT1 without spending $300 each time to go to a lab.
Anyway, I decided to give the VT1 test a shot the other day. I went to the gym and got on a stepmill with my Polar H7 HR monitor on, and after a 20-minute warmup, did 5 minute increments from intensity levels 1 to 10, where I during the last 2 minutes of each 5 minute increment, recorded my R-R data using HRV+ app on my iPhone.
What is nice about the app it not only gives you HRV test results in the usual metrics, but also lets you export the raw data to an email address. I took the raw data in excel from each test increment, calculated the RMSSD values (easy google search will reveal calculations – https://www.alancouzens.com/blog/HRV_Calc.html). Then I plotted the RMSSD values vs. HR at each test interval. My resulting plot matched the expected shape like you see in the attached screenshot. The point where the slope leveled off was very distinct, yielding a VT1 about where I expected it to be- not posting plot just yet.
I am getting a Gas Exchange and Lactate test done at a lab tomorrow and I am going to simultaneously repeat the HRV test with the iPhone to see how its result matches the crossover and lactate threshold points for AeT. Once done, I’ll post the actual results.
What I am hoping is, this might be an affordable and easy method of doing lab-free AeT and AnT testing. At least if it works, it will be possible to easily do re-tests every couple of months throughout training to objectively check progress.
Curious to hear what you pros out there think (Scott, Steve, Scott?). Everyone else feel free to chime in too!