A target respiration rate is determined for a user where, when the user breathes at the target rate, the user's vagal tone is improved, which provides a physiological benefit to the user, e.g., stress reduction without drug intervention. The user is directed to breathe at different rates while heart rate and breathing rate are measured. A value representative of vagal tone is generated from the measured heart and breathing rates for each directed breathing rate. The breathing rate that produced the lowest generated vagal tone value is determined to be the user's target respiration rate.
