Question

How can I keep up my strength as I get older?

At 67, I'm losing strength fast. I can't handle nearly the amount of weight I could even 10 years ago, and after I passed 65 I seemed to be getting weaker faster. At my age, should I use light weight and high reps, or heavy weight and low reps? Should I do multiple sets or just one set to failure? Or, should I stop weight
training and go with push-ups, deep knee bends and sit-ups?

Noel Granzow, Phoenix, AZ