Validation and Verification of the Running Power-Performance Decoder (PPD-R) - INSCYD

Validation and Verification of the RUNNING Power-Performance
Decoder (PPD-R)

INSCYD PPD-R technology

Prior to the release of the Running Power-Performance Decoder (PPD-R), INSCYD had two independent organizations join forces to carry out a scientific research project to capture data which can be used to verify and validate the new PPD-R technology.

The CREPS Aquitaine (a governmental national high performance sports center in Bordaux, France) sent one of their scientists to Switzerland to partner up with team member of the Spital Münsterlingen (a local hospital owned by the Swiss government).

This project was established to test the validity, reliability as well as the robustness and sensitivity of the calculations of the PPD-R technology. Read the results of this research project and have a unique look behind the curtain of the testing and technology validation.

METHODS

This section explains the structure of the validation study. Learn more about the participants, the testing protocol and the measurement tools used.

Subjects:

A total of 30 subjects participated in the overarching study of which 18 subjects participated in the PPD-R specific study (9 male, 9 female, 174,4 cm ± 10,0; 67,9 kg ± 9,7). However, because of the harsh climate conditions in December in Switzerland, not all subject were able to complete all tests. Therefore, some tests show a diminished number of subjects (14).

Body Composition:

Body composition of each subject was analyzed on the day of the first test using a Tanita BCN 545 segmental bio impedance body composition analyzer. This is a conventional body fat scale, commercially available for consumers.

Efforts:

Each subject completed several efforts of different durations and intensities on several occasions:

Occasion 1
  • 1x maximum sprint test of 20s (n=18). The subjects needed to rest at least 5min before and 10min after the sprint.
  • 3x sub-maximum efforts of approx. 6min each (n=14), intensity ranging from low lactate levels (below MLSS speed = <2 mmol/l) to submaximum but above MLSS speed with lactate concentrations >5 mmol/l.
  • 1x maximum effort of approx. 3min (n=14)
  • Body Fat and Body Fat measurement
  • Occasion 2
  • 1x maximum sprint test of 20s (n=18). The subjects needed to rest at least 5min before and 10min after the sprint.
  • All efforts were performed outdoors on flat public bike & pedestrian paths, under clear sky. The subjects warmed up for 10min before the start of the test.

    Lactate analysis:

    For the long efforts (6min & 3min) lactate values were taken before and immediately after the effort. More lactate values were taken after 1’, 2’,3’, 5’,7’ and 10’ minutes after the effort.

    For the two sprint efforts (20s) lactate values were taken 3 times before the sprint and for ten minutes after the sprint on a minute-by-minute basis. The lactate samples were analyzed using an EKF Biosen S-Line Analyzer, which was serviced by EKF just before the start of this study.

    Gas analysis:

    During the 6min and 3min efforts gas analysis was performed using a Cosmed K4 mobile metabolic analyzer. We used two identical analyzers with usage being alternated between those two. The analyzers were serviced at Cosmed France and new oxygen sensors were installed prior to the start of this study. Furthermore, analyzers were calibrated before each trial using A) a calibration gas (5 % CO2, 16% O2; Airgas LLC, Plumsdale, USA) and B) a volume calibration with a 3L manual pump.

    GPS & speed analysis:

    Speed and distance were measured using a total of 6 different commercial GPS watches (Garmin Fenix, Garmin Forerunner, Polar Vantage M, Polar Vantage V, Suunto 3, Suunto 5) and a Catapult Vector GPS tracker.

    Data recording was set to 1sec on each device. Where possible GPS and GLONASS was used parallel.

    Garmin used for INSCYD running validation
    Garmin GPS watch

    DATA ANALYSIS

    Now that you know more about the efforts, the protocol and the measurement tools, you can imagine we collected a lot of data. What did we do with this data? Read it here.

    1) Measured physiological data

    The measured physiological data contains data that is measured by the blood lactate analyzer or the gas analyzer.

    Sprint efforts:

    The 20s sprint efforts were used to capture the maximum lactate concentration.  

    6min & 3min efforts:

    The efforts of occasion 1 were used to:

  • Measure the VO2max of the athlete in the 3min all out effort, using a 25s moving average analysis in the 3min effort. (Cosmed gas analyzer)
  • Calculate maximum fat combustion rates using the lactate values and gas analysis data of the three 6min efforts.
  • 2) Calculated data

    The calculated data contains data that is calculated by the Running Power-Performance Decoder (PPD-R) technology. These calculations are solely based on GPS data.

    Sprint efforts:

    The GPS data recorded during the two 20s sprints were used to calculate the glycolytic power [Watt] as well as the VLamax [mmol/l/s] of each athlete. Calculation was done using the speed data of the commercially available Garmin Fenix watch.

    We then used the calculated VLamax – derived from the GPS data only – to calculate the theoretical blood lactate concentration after the sprint.

    3min efforts:

    The 3min effort was used in combination with the sprint efforts to calculate the VO2max of the subjects. Similar to the calculation of VLamax this is based solely on the GPS data of the Garmin Fenix Watch.

    FatMax:

    Maximum Fat combustion rate was calculated only based on the VO2max, body fat and VLamax values.

    Catapult Sports Vector for INSCYD power performance decoder running
    Catapult Sports Vector

    RESULTS

    It’s time to look now at the results. Remember the aim of this project – To test the validity, reliability as well as the robustness and sensitivity of the calculations of the PPD-R technology. Let’s start with the validity of the PPD-R technology.

    “The validity is about the accuracy of a measure.”

    Validity of the solely GPS based VO2max calculation:

    The calculated VO2max did not differ (p<0,05) from the measured VO2max, R2= 0.96. The differences between measured and calculated VO2max values were 1.43 ml/min/kg ±1,09 and therefore within the accuracy of the used Cosmed K4 analyzer.

    That means that the VO2max results of the Running Power-Performance Decoder – which are solely based on GPS data – do not differ from the VO2max results of a “golden standard” Cosmed K4 mobile metabolic analyzer. In other words: the PPD-R VO2max is accurate (valid).

     

    Validity of the VO2max in PPD-R. Comparing PPD-R results (y-axis) with “golden standard” Cosmed metabolic analyzer results (x-axis).
    Fig 1: Validity of the VO2max in PPD-R. Comparing PPD-R results (y-axis) with “golden standard” Cosmed metabolic analyzer results (x-axis).

    Validity of the solely GPS based VLamax calculation:

    Recalculating measured lactate levels after the 20s Sprint test (based on GPS data) showed good agreement with the measured lactate concentration (p<0.05, R2=0.84).

    That means that the VLamax results of the Running Power-Performance Decoder – which are solely based on GPS data – show good agreement with the actual blood lactate measurements. In other words: the PPD-R VLamax is accurate (valid).

    Validity of the VLamax in PPD-R. Comparing PPD-R results (y-axis) with actual lactate measurements (x-axis).
    Fig 2: Validity of the VLamax in PPD-R. Comparing PPD-R results (y-axis) with actual lactate measurements (x-axis).

    Validity of the calculated maximum Fat combustion rate (FatMax)

    The calculated FatMax was in good agreement with the FatMax derived using the VO2 and lactate data from the series of 6min efforts (p<0.05, R2=0.89).

    That means that the FatMax results of the Running Power-Performance Decoder – which are solely based on GPS data – are in good agreement with the FatMax results, based on VO2 and lactate measurements. In other words: the PPD-R FatMax is accurate (valid).

    Validity of the FatMax in PPD-R. Comparing PPD-R results (y-axis) with results based on VO2 and lactate measurements (x-axis).
    Fig 3: Validity of the FatMax in PPD-R. Comparing PPD-R results (y-axis) with results based on VO2 and lactate measurements (x-axis).

    The validity results show that the new PPD-R technology is accurate. But do we get the same results when comparing sprint data of occasion 1 with sprint data of occasion 2? In other words: can we reproduce the same results on another occasion? This is a question about repeatability that will be answered by the reliability results.

    We tested the reliability of the 20s sprint, because this is the most novel test. Let’s have a look at how good the PPD-R can reproduce GPS based running VLamax / glycolytic power!

    “The reliability is about the consistency of a measure.”

    Reliability of the calculated glycolytic power using the 20s sprint efforts

    The calculated glycolytic power did not differ in the 2 testing occasions. We observed a high agreement between both occasions (p<0.05, R2=0.81).

    That means that the PPD-R results between the 2 sprints do not differ. This is as expected, since we do not expect glycolytic power to change between 2 occasions that took place within maximum 4 days. In other words: the PPD-R results are reliable.

    Reliability of the PPD-R results. Comparing PPD-R results of occasion 1 with occasion 2.
    Fig 4: Reliability of the PPD-R results. Comparing PPD-R results of occasion 1 with occasion 2.

    Last but not least, we’ll have a look at the robustness & error sensitivity of the PPD-R technology. This will answer the question: how much do the PPD-R results change when we change the body fat or GPS data a little bit.

    Robustness & error sensitivity:

    All GPS derived calculations include information about the body composition. In this study only the body fat was measured. Such measurements may be subject to variations. Therefore, we investigated the robustness of the calculation to a projected error / deviation in the body fat measurements. For this we used the dataset of one subject to simulate the error caused by deviations in the body fat measurements.

    As Figure 5 shows: even large deviations in body fat measurements do not change PPD-R results (VO2max, VLamax, speed at MLSS, FatMax) dramatically. In other words: to get accurate PPD-R results, we don’t depend on what exact body fat measurement is used. (note: the “steplike” appearance of the curve is because of the rounding of the results)

    Robustness & error sensitivity of the PPD-R results. Large deviations in body fat (x-axis) only have a small effect on PPD-R results (y-axis).
    Fig 5: Robustness & error sensitivity of the PPD-R results. Large deviations in body fat (x-axis) only have a small effect on PPD-R results (y-axis).

    Another possible source of error is the distance measured via the GPS watch, which is used to calculate the running speed. Therefore, we calculated the error created in the VO2max calculation by a deviation of the measured distance in the 3min effort.

    “Robustness is about getting a stable outcome, despite an expected range of error in the input”

    This sensitivity by itself matches with the average deviation of measured vs. calculated VO2max. In other words: although you should always try to avoid GPS data errors, they only have a small effect on PPD-R VO2max results.

    Robustness & error sensitivity of the PPD-R VO2¬max results. Deviations in GPS measurements (x-axis) only have a small effect on PPD-R VO2max results (y-axis).
    Fig 6: Robustness & error sensitivity of the PPD-R VO2¬max results. Deviations in the GPS derived distance (meters) (x-axis) only have a small effect on PPD-R VO2max results (y-axis).

    WRAP UP

    This article showed you how we conducted the validation study. We shared insights about the subjects, methods and analysis. Last but not least you received the validity, reliability, robustness & error sensitivity results.

    This article showed you how we conducted the validation study. We shared insights about the subjects, methods and analysis. Last but not least you received the validity, reliability, robustness & error sensitivity results.

    Not convincing enough ? Have a look at the raw testing data of the PPD-R. Click here to download the validation study raw data.

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