Train.Red is a Dutch company that makes wearable muscle oxygen sensors for sport and research. Its FYER sensor is worn over a muscle and sends live readings to connected devices.

How it works

Near infrared lights shine into the tissue beneath the skin. Oxygenated and deoxygenated blood absorb the light differently. The returning light is used to estimate muscle oxygen saturation and blood volume. The graph shows how quickly a specific muscle uses oxygen and recovers, supporting pacing and recovery.

Key considerations

The reading describes a small area beneath the sensor, not the whole body. Placement, skin thickness, movement, pressure and outside light can affect results. Values also differ between muscles and people, so personal trends are more useful than universal targets. Interpretation requires experience and context from workload and heart rate. Train.Red supports performance analysis and does not diagnose circulation, muscle or metabolic conditions.