I love this discussion. @rodkleiss thanks for starting it. I have a few things to add.

If you like research and evidence-based knowledge on aging and fitness, wellness, exercise and a ton more, I recommend checking out :
- McMaster Optimal Aging Portal https://www.mcmasteroptimalaging.org/
It is run by McMaster University in Hamilton, Canada.
Here's the section on Exercise https://www.mcmasteroptimalaging.org/age-well/healthy-lifestyles-and-wellness/exercise

My husband and I do HIIT (high-intensity interval training). It's a great way to fit in a workout in a short period of time. We follow a classic workout for boxers, working out 4 times a week on this schedule:
Monday - cardio and light weight combos
Tuesday - sprints
Wednesday - strength
Thursday - day off, stretches and walking
Friday - cardio

Five weeks on and one week off.

I'm pretty proud to say that I still do burpees. (I still don't like them, but proud when they're done. 🙂 )

I've added a lot more stretching and light mobility warm-up exercises BEFORE working out now. That has become imperative to reduce risk of injury.

Do you mix up your workouts to keep it interesting? What's your favorite workout?