I am 55, weight and height proportionate. I have been exercising consistently since my 20s. I want to have definition, not bulk. It certainly gets harder as you age and my skin isn't as, let's say, firm as it used to be. Is Pilates a better choice than weights, or should I alternate workouts? I have been alternating my weights with stationary bike riding but things continue to go southward.
Thanks

Definition in your muscles is more apparent from having a low body fat percentage. You need to have a diet which will help lose any extra love handles you are carrying.

Pilates are good buy Weight lifting is better.

High repetitions (10+) is needed to create more definition. You should be doing about 4 sets of 10+ reps and it should be so easy that you can accomplish the last rep on your last set with ease.

Good luck and keep us informed.