: Along with the good suggestions above I recommend cross training
: with a bicycle fitted with clipless pedals.

Should you go clipless be aware there are two types.

External cleat ala Look system. This is a big cleat on the bottom of your shoe which causes you to walk on your heel with your toes an inch or more off the ground. If you stop somewhere for a coffee the slippery floor will do you in. You must walk with a baby step, prancing kind of motion and even then you are going to go down once in a while. The silver lining to this cloud is you will be so embarrassed you will want to get up as soon as possible; this will exercise your hip flexors to the max.

Internal cleat ala SPD system (Shumano). The small cleat is built into the sole of your shoe. You never even feel they are there.

I started with the look system and could not get rid of them fast enough. I love the SPDs.

~Bob