In a fog, thinking about how to meet the federal guidelines for 2½ hours of moderate exercise per week, I bumped into my neglected bicycle in the garage. Tires flat. Shine gone. Brakes sticky. Chain strained.

That sad scene unfolded in March. By mid-April, my 12-year-old bike sparkled after a $125 tuneup at a local bike shop. A new $27 chain added efficiency and enjoyment to my revived neighborhood rides. I also replaced my helmet after learning head-protecting materials lose their integrity over time.

Ideally, these investments will boost my chances of more frequently meeting weekly goals for moderate exercise.…