“Saintey asks me to breathe in time with the blue bar – five seconds in as it fills, five seconds out as it drains. Then something striking happens. Within a few seconds, the difference between my lowest and highest heart rate is much larger than before – varying from about 60 to 90 beats per minute. And the line on the graph transforms from ugly random spikes into a smooth, snake-like curve.”

“Saintey asks me to breathe in time with the blue bar – five seconds in as it fills, five seconds out as it drains. Then something striking happens. Within a few seconds, the difference between my lowest and highest heart rate is much larger than before – varying from about 60 to 90 beats per minute. And the line on the graph transforms from ugly random spikes into a smooth, snake-like curve.”

— Jo Marchant