Everyone who plays golf is an athlete. Golfers make movements specific to the game which have little to do with how they move in daily life. Part of learning to play golf is learning how to make those movements to play effectively. The other part is learning to how to make those movements to avoid injury.
Golf injuries of the lower back have been extensively studied. The lower back is stressed most in making a swift and violent turn into the ball on the downswing. Current swing theory directs that the difference between the hip turn and shoulder turn on the backswing. The greater the difference, the more the lower back is loaded with unnatural pressure. The inconsistent swing which is characteristic of recreational golfers can cause a sudden, unexpected, and excessive load to be applied to the lower back. A lack of physical fitness leaves the body unable to resist these stresses which leaves the body open to injury.
My lower back is in terrible shape, yet I have played pain-free golf for years. This is how I do it. Please consider these ideas for yourself, regardless of the state of your back.
The foundation of my full swing is tempo. Tempo is the speed at which the hips turn. It must be the same swinging back and swinging down. When the tempo of the hip turn stays constant, not only do you hit the ball better, but you prevent sudden stresses from being applied.
I take my stance by bending from my hips, not from my waist. Bending from your waist throws weight onto the lower back.
On the backswing, I turn my hips so the maximum difference between my hip turn and shoulder turn is about 20 degrees. (Professional golfers have a difference of 45 degrees or more.)
My swing itself is led by a full body turn and powered by holding on to my wrist set until the momentum of the downswing naturally releases the clubhead into the ball. I see so many recreational players lurch into the ball as a way of hitting hard, that I wonder just when the shoe is going to drop, if it hasn’t already.
Your finish position can subject your back to considerable twisting. I would recommend that hold your finish position infrequently as a check, and never routinely when practicing or playing. Always release yourself to a neutral upright position with your hands in front of you as you watch the ball, just like Phil does.
In addition, you can do these things to protect your back.
Warm up carefully. Stretch and turn lightly and gently before you even pick up a club. Begin to swing by taking a driver and making long, slow, and I mean slow, swings, to gradually warm up your turning muscles.
Start going through your bucket by hitting a few pitches with a half swing. Work your way through the bag from your short clubs up to your driver.
During the round, stretch out every four holes or so. You make a full swing only every few minutes and you can stiffen up before the round is over.
Walk around the course with your clubs on a pull cart. Carrying your clubs compresses the spine. Riding in a cart can subject your spine to impact stresses when the cart goes over bumps.
Golf is our recreation, not our livelihood. Play it so it introduces joy into your life instead of pain.