Generally speaking, the best exercise for you is the one you enjoy the most. Remember, this is about health optimisation and not performing at the next Olympics. The important thing is to remain safe and increase your effort gradually. Fluid movement exercises (such as Cross Trainer, Rowing Machine, Walking, Gentle Weight Bearing Exercises, Mini Trampoline, etc…) can help you work up a sweat without impacting your joints. The secret to exercise is simple – it is to make a start.