What does a guy do when an exercise routine has failed?

Double down.

My routine for many years was to start the day with a fast mile. 15 minutes. Sometimes 12. Now, 4-mph or 5-mph may not seem fast, but try walking a mile in 12 minutes.

Yeah, sure, I can run the same distance in about the same time, but effort is involved. OK, maybe run is the wrong word. Trot? Shuffle?

Regardless, that routine worked up some sweat, kept the muscles moving, and got heart rate up to 90-percent of my maximum.

Double down did not mean a 6 minute mile but a 15 minimum mile twice a day. Double the exercise. The mild fatigue and labored breathing did not go away.

Maybe the problem was diet.