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Product related FAQ's

The sensor is always on and ready to connect.

- If the blue display diode is blinking every 2-3 seconds, your sensor is on and ready to connect.
- If the blue display diode is blinking rapidly, your sensor is connected.
- If the display diode is not blinking, the battery needs to be charged.

When the sensor is fully charged it will be ready to connect for up to a week.
When the sensor is fully charged it can measure up to 8 hours.

Keep in mind that this duration will decrease if you start your training session 3 days after a full charge.

The sensor is water resistant

However, we do not recommend submersing the system completely. This means you can not go swimming with the system.

Data related FAQ's

TSI is an abbreviation that stands for Tissue Saturation Index.
It represents the amount of oxygen in your tissue.

Typical rest values lay between 55% and 75%.

HbDiff is the hemoglobin difference, the difference between your oxyhemoglobin and deoxyhemoglobin levels.

With our light-based technology, we measure changes in light and calculate changes in oxy,- and deoxyhemoglobin based on the modified Beer-Lambert Law. Learn more about NIRS under this

With pulse oximetry, you measure the oxygen saturation of your blood. This is an indication of the functionality of your respiratory and cardiovascular systems. It represents the ability of your body to transfer oxygen from the air to your lungs, from your lungs to your arteries, and onwards to any organ.

We do not measure blood, we measure tissue. This does not represent the functionality of your respiratory and cardiovascular systems but shows the efficiency of your (muscle-) tissue in extracting oxygen from the arteries.

Shipment related FAQ's

Our processing time is around 2 working days after your order.

Yes, we compensate our carbon emission for packages we ship. We try to compensate the emission for all packages we receive from our suppliers.

We are based in the Netherlands.
The shipment cost is dependent on the region you're buying from.

The table below indicates the associated costs per region.


Our sensor connects via Bluetooth Low Energy to your smartphone. Make sure Bluetooth is enabled in order to connect.

Allow location services and GPS to run in the background to integrate distance-related metrics to measured and synced with your NIRS data. We do not track these metrics when the Train.Red app is not measuring.

Bluetooth enabled and GPS switched on but still running into issues?
Go to:
Settings > Apps&Notifications > Train.Red (or select all apps to open and scroll to Train.Red) > Storage & Cache > Clear Storage & afterwards Clear Cache.

Restart phone and let's try again!

We measure local oxygen saturation based on hemoglobin differences in your tissue.

This data is translated into features that allow quick adjustments of your training, based on the real-time physiological data we measure.

The placement of your sensor is of significant importance. A wrong position and your data is not informative or even usable.

Make sure you're measuring on a relevant position on your body, on bare skin. During cycling this can be your upper leg, or when in the gym, your bicep.
Naturally, you're free to place the sensor wherever you like, but keep in mind that not every muscle is equally involved during certain activities.

We highly recommend to perform the 'position check' after you have specified your area of interest. During this position check we compare your desaturation with our database and make sure the device behaves as expected.

In bright day light we recommend to use our daylight protection patches. These patches prevent ambient light to interfere with the light transmitted by our sensor.

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