There were a few other signs of declining fitness I was noticing last summer that troubled me. One was that my gut was getting big enough that I was less flexible in the middle. Second, I was slower to get up from a seating position, whether from a chair or from the floor of my house (a frequent place to sit when you have young children). Third, the stairs at work were leaving me winded.
As an admitted running snob, these realizations galled me (apparently I could pull off being a running snob without actually running). I knew my health and fitness levels were not where they should be, and that things would not improve unless I took action.
I had to start basically from ground zero. Rather than go out and pick up a nice case of shin splints in the first week, I started by walking to re-establish the exercise habit, and gradually adding running segments of as little as 1-2 minutes at the beginning, gradually increasing in number and length. This was NOT easy. One minute of running at a slow pace was my limit; two minutes left me winded.