Take your physical limitation into consideration
if you have problems with your joints you may want to consider such options like
rowing
swimming
elliptical
biking
walking (if no pain is experienced)
First things first, test yourself and your abilities
Start with your baseline of total time able to exercise:
example: 5-10 minutes of biking
seniors (if difficulty walking long distances): test using step-ups or step-downs
refer to videos on Resistance Training tab
General population: complete workouts
1-2 times each week
Seniors: complete workouts 2-3 times each week
Increase the duration and intensity of the exercise every 1-2 weeks
Make adjustments based on your own personal goals
take into consideration time, resources, facilities available
refer to image below for FITT Principle Guidelines