If you wanna look strong, go to the gym. But if you wanna be strong, do military workouts. Lets be real, most guys over 40 go to the gym to look strong, but they can't do 10 pushups. That's not real strength, that's not real training.
How old is your father?
Calisthenics and body weight exercises are good. I do some weight lifting tooFor pushups I can do about 50