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.
Below is a comparison of breathing rates for various other activities.
Clearly my zazen practice is characterized by a slower breath rate compared to other activities during the day.