HRV4Training measures your Heart Rate and Heart Rate Variability features while guiding you through a simple test (lying down and standing right after waking up), which can be used to determine your training state and prevent overtraining.

Higher orthostatic HR values (i.e. the difference between your heart rate while standing and your heart rate while lying down), as well as reduced heart rate variability (in terms of both time and frequency domain features, for example reduced SDNN or HF) can signal overtraining. If you see these trends going up, take a day off from training. During recovery weeks you should see HRV going up again, as well as orthostatic HR going down. Ideally, you should measure your average values for 1 or 2 weeks of low intensity training, and then compare against this baseline.

Extracted and stored features while lying down and standing:
- Heart rate,
- Mean of beat-to-beat intervals (AVNN),
- Standard deviation of beat-to-beat intervals (SDNN),
- Square root of the mean squared difference of successive R-Rs (rMSSD),
- Number of pairs of successive R-Rs that differ by more than 50 ms (pNN50),
- Low frequency power (LF, 0.04-0.15 Hz),
- High frequency power (HF, 0.15-0.40 Hz),

The time window used to compute features can be configured choosing between 1, 3 and 5 minutes.

HRV4Training has been tested with Polar H7, mio alpha and Armour39 heart rate monitors, but should work with any bluetooth low energy (or bluetooth smart, i.e. BT 4.0) heart rate sensor.

If you do not have a Bluetooth low energy heart rate sensor, HRV4Training can calculate your heart rate using the phone camera.