A friend of mine went into cardiac arrest some months ago while he was on a run. The ensuing surgery placed a stint in the pipeline that supplies blood to the heart. Not the technology of the Bionic Man, I find it no less awesome, where “awe” is the particularly appropriate prefix.
As he’s building himself towards a renewed running regimen, he explained to me that he wants to monitor his heart rate during exercise. The key is to stress the heart so that it works just hard enough to fix what’s broken, strengthening what was mended, without breaking it again. There is a fine line.
I suppose that this is the perennial and universal task. We are all working to push ourselves just hard enough to mend what’s broken, but not so hard as to break the heart again.