To compare respiration rates for meditation and non-meditative activities, I recorded my breath using a Vernier LabQuest device connected to a gas pressure sensor and a respiration monitor belt. the first plot below shows my respiration sitting quietly and reading. The second plot is a recording of meditation during the 7th day of a meditation retreat.
Respiration while sitting quietly and reading. Breath rhythm was variable. Occasionally I took a deep breath. Average breathing rate was 14.6 breaths/min.
Breath recorded on the 7th day of a meditation retreat. Breathing rate was 2.85 breaths per minute.
Below is a comparison of breathing rates for various other activities.
Comparison of respiration rates for various activities, including meditation.
Clearly my zazen practice is characterized by a slower breath rate compared to other activities during the day.