A concept which is beginning to gain popularity across the both the psychological and physiological world is the concept of heart rate variability (HRV). HRV is exactly what the name implies- variability of the heart rate. Heart rate varies slightly at rest, rather than having a metronome like quality, or, at least, experts are saying that’s what should happen. Having a varied heart rate implies an organism is both healthy and resilient.*
Resiliency is a measure of how well someone deals with stress. It also implies emotional variability. Like HRV, too much variability equals instability, but having the ability to go from calm, to a little less calm, to slightly emotional is better than, say, calm to jagged crying fits. A range of emotions is good, just like variation between heart beats is good.
Variation is also important physically. Having joints that are accustomed to moving in a variety of ways is thought to be a protective mechanism against injury. Again, too much movement without control leads to instability in the joint structure, so while practicing controlled movement variation has protective properties, stretching until you feel like the muscle is going to rip off the bone in an attempt to improve flexibility might not.
It should come as no surprise exercise improves HRV. We also know exercise improves our psychological sense of well-being, and (hopefully) improves our capacity to move in a variety of ways. What is fascinating (at least to me), is the idea that what’s best for our physical well-being is also what’s best for our emotional well-being and the direct impact they have on each other via our physiology. The mind and the body affect each other, which is something worth considering when you take stock of how you feel mentally and what you are experiencing physically.
*A good article on this can be found here: https://www.heartmath.org/articles-of-the-heart/science-of-the-heart/article-explains-importance-of-heart-rate-variability-for-your-health/