People are often amazed at how quickly their physiology can change from a meditation technique.
The video display my beat-to-beat heart rate while I am playing a game on my computer and then start meditating. When playing the computer game my heart rate is in the 50’s, so I am clearly relaxed. However, my heart rate variability associated with recovery from stress is not very high. At the 8:49:15 timestamp seen in the lower right corner of the screen I stop the game and shift my attention to enjoying the breath for about a minute. My heart rate pattern changes instantly with my heart rate speeding up as I inhale and slowing as I inhale. That heart rate pattern is associated with a faster rate of recovery. So even a minute or so of practice will have a beneficial physiologic effect.
For those wondering the app is HRV Train running on an iPhone.