Beware of the One Size Fits All workout routines. What's good for the goose isn't always good for the gander. What works for one person does necessarily mean it will work for you. Different body types, age, health conditions, and gender could all affect the outcome you receive from exercising. Some people swear by group classes like, soul cycle and cross fit or workout videos like PX90 but participating in these fitness activities won't necessarily give you the results you are looking for. Granted, doing these is far better than sitting at home doing nothing. The problem with some of these One Size Fits All exercises is the lack of variety for certain fitness levels.
Someone who hasn't been in a serious workout routine for three years should not be expected to complete the same difficult exercises that someone who has been training at a consistent level is doing. You risk this person hurting themselves doing something they are not physically ready to do. You also risk that person losing the desire to continue with such a vigorous exercise style. This tends to be one of the key reasons people quit training or never begin in the fist place. It is extremely important for someone beginning a new regiment, that they do something tailored to their needs and current fitness level. This way it keeps them encouraged and reduces the chance of them injuring themselves. They can ways progress and increase the difficulty as time goes on.