good call, there is also the fear factor which many men will not admit to. Frightened if they push their heart in any way, it will cause damage.
Apparently you are aware of the importance of an exercise routine, but you are unable to persuade your father. Is your father depressed? Some people just don't care, and don't feel it is worth while; may be an exercise in futility to try and convince.
Is your Father on any medication and does he have any known heart problems or other physical issues?
How old is your Father?