I am 60 and having been working out with Cathe pretty consistently for many years. I own pretty much every workout she has produced. Although my skin is aging and my body is changing in more ways than I would like in terms of external appearance
, my fitness level and my health on the inside has never been better. I am lifting heavier and feeling better in terms of cardio - as long as I take my rest days and do lots and lots of stretching. I personally feel that age is not the biggest factor in determining how intense to go with one's workout choices - it is more a matter of matching the workouts, number of rest days, number of high impact days and intensity level to how you are feeling that day, your medical history and/or current issues, your goals and your fitness level.
My favorite series is XTrain. I am currently doing the 90 day rotation and having a blast. There is so much variety in those workouts - almost no moves are repeated. I love the music, the longer stretch segments and the fact that it is a compete package - heavy weights, lighter weights, steady state cardio, low impact hiit, high impact hiit... It has it all. Cross training at it's best! Cross training is critical at any age, but especially important at my age when I don't want to overdo it. At this point I don't have any physical restrictions so I can work pretty hard, but it is easy to modify the workouts using lighter weights, shorter premixes, etc. if you need to.