Exercise Physiologist Tero Joutsen, PhD, rideson the treadmill during a 30min constant load test – the gold standard for validation of the maximum lactate steady state (AKA anaerobic threshold / FTP)

Advertising claims are often designed to make more out of products than they actually are. INSCYD’s Power-Performance Decoder (PPD) software doesn’t have a claim. Instead of making bold promises we’d rather have our customers try out PPD themselves. This is the story of someone who went forth to test the accuracy of this unique system – undercover.

Mixing Scepticisim and Curiosity

Tero Joutsen is an exercise physiologist at Finnish KIHU – Research Institute for Olympic Sports and Sports Lab Jyväskylä. He is very critical when it comes to training and performance diagnostic gadgets – but nevertheless very interested in innovations that enable him to understand the respective athlete’s unique characteristics better and to design training plans that match their individual needs perfectly: “When I found the offer of a free trial of PPD on social media past April, I decided to give it a try”, he recounts.

 

Joutsen downloaded the PPD test protocol – a procedure that generates performance data of lab-like accuracy by a simple field test – from the public facing INSCYD website (PPD protocol free download).

 

After completing the test, he sent the data and a rough guess of his body composition to INSCYD for an analysis, following the standard procedure. What wasn’t standard was that Tero Joutsen was planning on doing a lab test afterwards to double-check whether the field data was really in line with the lab data. (Which is great as we appreciate people putting us to the test. What could be more motivational?)

“In the beginning I had some doubts if it will work because it uses only power data, therefore I decided very early on to do a lab test as well”, says Tero Joutsen. First, he did the PPD test over a period of three days, then he went to the KIHU laboratory for some more testing. Shortly after completing the PPD protocol he carried out:

 

  1. A ramp test till exhaustion measuring oxygen uptake throughout the whole test – the standard procedure to measure VO2max.
  2. An incremental test using a metabolic cart to measure fat and carbohydrate combustion.
  3. A series of constant load tests: the gold standard to find the true maximum lactate steady state AKA anaerobic threshold. Each test consists of 30 minutes of constant load during which it is observed whether lactate remains in steady state or not. MLSS signifies “maximum lactate steady state”, a factor that all other tests try to estimate as threshold, FTP or the like.
 

So, what was special about Tero Joutsen’s test was that he did not compare a threshold “estimate” (PPD) with another (e.g. threshold, FTP …), but validated PPD with the most accurate lab test available so far.

The best comparison one could imagine: Tero used the same bike, the same powermeter and even rode his bike on a treadmill instead of a stationary bike in order to make the lab testing as similar as possible to the outdoor testing.

“The fact that the fat and carbohydrate curves were basically identical striked me”

— Tero Joutsen, KIHU Research Institute for Olympic Sports

The Results

Very straight forward his results were:

 

  1. VO2max: INSCYD’s Power-Performance Decoder = 61.96 ml/min/kg vs. Lab Testing= 60.5 ml/min/kg.
  2. Maximum lactate steady state aka anaerobic threshold (FTP): PPD= 292 Watt vs. Lab Testing= 284 Watt.
 

This is an amazing result, considering that the testing was carried out on different days and that can be small differences in lab vs. field testing. It also needs to be considered that the common standard lactate threshold tests in the lab tests have a typical error rate of five percent when it comes to threshold determination, in case of some unfavorable combinations of test protocol and evaluation model even more than ten percent. A regular VO2max test shows a typical measurement error of 2% to 4% in terms of reliability, mainly because of the accuracy of metabolic carts/VO2 analyzers.

Taking it one step further: Fat & Carbohydrate combustion rates.

Fat and carbohydrate combustion is both of pinnacle importance to many coaches and athletes and also what people are most skeptical about. In Teros test the calculated fat- and carbohydrate combustion curves of the PPD were basically identical to what Tero found using the metabolic cart in the lab of the KIHU institute.

“The fact that the fat and carbohydrate curves were basically identical striked me. I mean, calculating a threshold value out of power data is nothing mind blowing. And the good match of the VO2max might just have been a lucky punch. But calculating the correct fat and carbohydrate curve for each single step of the lab test – that was something different to me”, says Joutsen.

Comparing the Fat and Carbohydrate values calculated by INSCYD vs. KIHU Research Institute for Olympic Sports using a metabolic cart in an incremental test. Note: at low power outputs there is a tiny difference between the fat combustion rates in the lab tests vs. the calculation of INSCYD. This is most likely because the lab data represents whole body fat combustion. In contrast INSCYD only shows the fat combustion rates of working tissue (muscles actively involved in producing power). The percentage contribution of non power producing tissue at intensities <150W is relatively speaking larger, therefore there is a slight difference in fat & carbohydrates visible.

This shows: PPD is clearly an extremely accurate testing tool that can keep up with lab testing results, especially as Tero Joutsen’s body composition was only estimated, which alters the accuracy of the measurement by a few watts, too.

 

“I was really surprised. At least in my case results were basically the same as in the laboratory tests”, says Tero Joutsen – and even more so as PPD calculated exactly the lab threshold of 284 when he used the lab VO2max value of the lab test instead of the value from the field test.

 

A fact that convinced him and his co-workers at KIHU’s. They are planning on using PPD at the institute/Sports Lab Jyväskylä: “PPD-test would be a very good alternative test method specially during the lockdown”, says Joutsen. “It will open the possibility to test more people because athletes don’t have to come to laboratory to do test.”

More INSCYD reviews:

  • Accuracy of the Power-Performance Decoder, by Molab