My 82 year old father suffers from regular bouts of muscle spasms in his back often from standing. What is the best way to treat and prevent?

Walk more stand less. Typically older individuals with these symptoms are suffering from degenerative disc disease, which is best treated by daily and several times per day exercise, primarily focusing on spine and lower extremity stretching, as well as low-impact cardio exercise. If walking is a problem, then a stationary recumbent bike or better yet, walking in chest deep water is excellent.