heart rate variability

Beat-to-beat fluctuations in cardiac intervals used as a noninvasive index of autonomic nervous system function and stress resilience.

Science

How Many Calories Does Playing Chess Burn?
ByJames McCallef February 9, 2026February 9, 2026

The answer to how many calories does playing chess burn is about 70 to 100 kilocalories per hour for an…

Read More How Many Calories Does Playing Chess Burn?
Health

The slow breath changing hearts: inside HRV’s quiet revolution
ByJames McCallef November 26, 2025February 4, 2026

In a quiet room a phone timer glows, a soft tone marks five seconds in and five seconds out. On…

Read More The slow breath changing hearts: inside HRV’s quiet revolution