The exercises (The Founder, Lunge Stretch, and an unnamed third one) promise to both reduce your back pain as well as improve your posture over time. Goodman helpfully explains the correct technique for each step, as well as exactly which part of your muscle should be feeling stretched or activated when you do a step. It’s great at letting you know if you’re doing it right or not.
Before you start, do note that if you have chronic back pain or are already seeing a physiotherapist, you should check with them first. You might also want to start with this other wall-based posture-correction exercise, which is simpler to do than Goodman’s methods. If you notice pain during those, you’re better off checking with a doctor before trying the Foundation Training exercises.