Performance diagnostics with NIRS



When dealing with the topic of performance diagnostics ("LD"), an almost unmanageable flood of different models, methods and test procedures opens up, which in most cases all claim to be "correct" and to offer the athlete added value. In fact, in many cases both points are to be critically questioned and in addition many of these diagnostics require access to a laboratory or at least access to some equipment and facilities to perform them. 

NIRS diagnostics, on the other hand, can be done at home or outdoors by yourself and provides individual, reliably correct results that can be used immediately for work and training. Also due to the favourable price, it is possible to carry out a NIRS LD regularly (more) than a diagnosis in the laboratory, which is often only done 1-2 times a year. With NIRS LD, you can respond more quickly to changes in your performance and always gear your training to your current abilities and needs.

Theoretical background

With the help of an NIRS sensor, the blood flow and the availability of oxygen in the muscle can be mapped. Put simply, it shows how much oxygen arrives in the muscle and how much oxygen is consumed by the muscle. This can be used both during training and in diagnostics. 

Basically, three different phases can be identified, which are shown in the following diagram:

  • Phase 1: rising oxygen saturation (SmO2)
      • The muscle is supplied with more oxygen than it consumes, so there is an increase in SmO2the supply of oxygen is greater than the consumption
  • Phase 2: stable SmO2
      • The supply of oxygen to the muscle covers the consumption of the muscle, the SmO2 is on a plateau / in a steady state →.
        the supply corresponds to the consumption of oxygen
  • Phase 3: decreasing SmO2
      • The muscle consumes more oxygen than it receives, the SmO2 therefore decreases (depending on the severity of the deficit) → the supply is
        the supply is less than the consumption of oxygen

In a step test, it is possible that all three phases occur (shown symbolically in the diagram below), but it is also possible that not all phases are passed. If, for example, the step test is started too intensively and/or the basic level is poorly developed, it is possible that phase 1 does not occur in the test run, i.e. a drop in SmO2 can be observed. However, phase 1 would occur at the latest when the test is stopped and the performance is discontinued, because the consumption of oxygen is significantly reduced and the supply is still at a high level (until breathing and heart rate have reached resting level again).

Carrying out NIRS performance diagnostics

Performance diagnostics using oxygen saturation is very simple compared to complex laboratory diagnostics. Basically, all that is needed is a gradual load and an NIRS to measure the oxygen saturation. A test can be carried out both indoors and outdoors as a field test, whereby maintaining a constant power/load/intensity without an ergometer or treadmill places higher demands on the individual pacing skills, which, however, is a skill worth learning and rewarding either way. 

It makes most sense to measure the performance-limiting muscles, but other muscles can also be used. Depending on the type of sport, the movement frequency (e.g. cadence) and length (e.g. sitting position) of the measured muscle should be kept as constant as possible throughout the test, so that changes in the NIRS parameters are not due to changes in length or movement of the muscle, but to changes in metabolic conditions. In practical terms, this means: during a LD on a bike, the sitting position should not be changed and, in particular, the patient should not stand up/ride out of the saddle. During a diagnostic run it is important that the gradient remains constant. The gradient is particularly constant on a tartan track, where it is usually 0%. However, step tests can also be completed well on a long, steady incline.

Example of a test procedure on the bike

An exemplary test procedure on the bike is outlined here:


  • Fix the Moxy on the thigh, for the most reliable values the sensor should be firmly taped on the Musculus rectus femoris (lat.: straight muscle of the thigh) to prevent slipping during the test.
  • Pair the heart rate sensor, roller trainer and Moxy with the end device (speedometer, watch, computer) and ensure that all devices output valid (resting) data.
  • Depending on the power level, start the step test at X watts and increase by Y watts every 3 minutes (a safe protocol is to start at 60 watts and increase every 3 minutes). The cadence and riding position should be kept as constant as possible throughout the test. 
  • Go to the end of the workout and save the workout after stopping the test.
  • Send the test file to for evaluation

In the figure above you can see an exemplary test sequence. The step test can be seen in the power data (green), the oxygen saturation (pink) and the heart rate (red) follow the gradually increasing intensity. Data on frequency would be ideal to explain any fluctuations in blood flow and/or saturation.  

In principle, tests can be carried out in a wide range of sports and disciplines, but at the moment we are concentrating mainly on carrying out and evaluating cycling and running tests, before gradually adding other sports in the future. If you are interested in other sports, please feel free to contact us, we are interested in cooperations and collaboration and could prioritise them if necessary 😉 We are looking forward to working with you in the future.


Quasi second-by-second "lactate measurement" on site

One of the most important arguments for the effectiveness of NIRS diagnostics is the continuous measurement at the muscle, i.e. the site of the event. Here, both during training and in performance diagnostics, what happens in the muscle is reproduced live, without the temporal offset of, for example, a lactate measurement and, above all, without further influences from outside: it is measured where the performance is achieved.
As a result, what was previously only indirect and difficult to assess becomes transparent: where exactly in the performance and muscle fibre spectrum is an athlete better or worse trained. This can also be seen in the following figure, where four different progressions of a step test can be seen, which lead to different evaluations - different, individual results although the performances are comparable. As a result of the NIRS diagnostics, our experienced diagnosticians can, with the help of the TRAINALYZER, identify distinctive breakpoints in the saturation curve and thus the current important physiological support points (maximum pyruvate deficit, maximum lactate steady state, minimum SmO2) and create training zones. In addition, the blood flow curve can also provide valuable information on the quality of the sitting position and frequency.

With this and the current saturation curve, not only can the design of the previous training be well assessed (e.g. too much / too little intensity, too little volume, ...), but above all the most effective individual training can be determined. individual individual training for the coming training phase.

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