Cold pressor test
The cold pressor test was carried out after controlled-frequency breathing and Valsalva maneuvers, results of which are not included in this report. Baseline measurements were recorded for 1 min, and during the cold pressor test while the subject placed his right hand in a 0–1 °C mixture of ice and water for 2 min while maintaining a steady, relaxed breathing pattern. Immediately following the test, the subject’s hand was removed from the ice water and warmed in a towel while recovery data were recorded for 2 min.