Unless you slam the ball down you have to bend over more. More strain on your hips, back, and shoulders. Watch the view of him from the front. His back is almost parallel to the approach.
Staying in shape will help, but when you have to bowl as many games a week as the PBA guys do, even staying in shape will only do so much.
Belmo is a great bowler, but he won't last much past age 35 bowling like that.
Golf doesn't put nearly as much strain on your hips and shoulders as bowling. And PGA guys have to walk 5 1/2 miles every day during a round. They are working out while playing. Bowlers sit more than they walk. Muscles are working off and on all day.
--------------------
ROTO GRIP, There is NO Substitute
Slow Feet, Soft hand = Lots of strikes