The twisting and pulling of the golf swing strains your back. You need to protect it by strengthening your abdominals as well as your whole core and lower back. I have found that the best exercise to work out all three is the plank. Try a simple daily routing of this exercise and you will experience great results.
Other abdominal exercises can also work out your “six pack”, but they come with side effects such as lower back pain; or the need for special equipment that you cannot have access to at all times.
Aside from helping strengthen and tone all of your abdominal muscles, plank exercises also exercise the other parts of your body that make up your “core” muscles including your hips and the upper back muscles that protect the spine. This gives you more stability and better balance and hence a much better posture.