What is Undefined

Generally speaking, a higher Heart Rate Variability (HRV) indicates less stress on the body and a better balance in the nervous system.

However, if your HRV suddenly spikes much higher than usual, it might indicate one of the following scenarios:

1. Heart Issues

If your HRV (RMSSD) consistently exceeds 300, it's not a good sign. It may indicate abnormal heart function (like premature beats) 😐. In such cases, it's advisable to consult a doctor for professional medical evaluation.

2. Overexertion

Athletes, particularly those in endurance sports, might experience an increase in HRV during periods of intense training. Typically, HRV should trend downwards. It's thought that a rise in HRV in these instances could be due to the body being overworked, leading to a 'forced shutdown.' This involves the parasympathetic nervous system stepping in for immediate recovery, but it doesn't necessarily mean the body has improved or is problem-free. In such cases, you might notice unusually high HRV readings during sleep for one or several nights.

The best approach here is to stop what you're doing and rest as much as possible.

3. Measurement Error

Inconsistencies in how smartwatches are worn can result in a single, abnormally high HRV reading, likely due to measurement error. Such instances can generally be disregarded.

In summary

The exact neural activity changes represented by excessively high HRV values are complex, and there's no unanimous conclusion in the scientific community. Therefore, StressWatch marks such high values as undefined.

It's recommended to consider these possibilities and interpret your HRV readings in the context of your own situation.