It's hard to imagine how having a more flexible calf muscle can help heal the terrible pain you are having on the bottom of your foot and heel, but two important structures in your lower extremity are connected anatomically.
This is such an effective strategy, it belongs in everyone's armamentarium for getting rid of plantar fasciitis. Watch this 5 minute video to see why this really works and how to stretch the right way.
If you are a mother of young children, this is an especially helpful tip for you-- get a great pair of comfy shoes that you only wear inside your house. Make sure they are no-socks-required and easy to slip on, to ensure you will want to wear them all the time.
Why? Because we often spend more time on our feet and walk more miles than we realize inside our home. (My activity tracker reports that I walk 1.5 miles everyday before I even leave my house, simply taking care of the household!)
While there is nothing wrong with going barefoot on a sandy beach or soft, grassy lawn, our feet were not designed for the unnaturally flat and hard surfaces that we live on.
Having a "house shoe" protects the injured plantar fascia ligament from the extra stress of unnaturally hard and flat floors, allowing our ligament the chance it needs to heal.
Even a good quality (not flimsy) flip-flop can be wonderful.
Even if your sneakers still look great, they are no longer providing you the shock-absorption your feet need if they have over 400 miles on them. If you exercise regularly, you most likely need a new pair about every 9-12 months, sooner if you have a heavy body weight or regularly exercise on concrete.