That’s a very good question. It might be helpful to think about your father’s level of activity before the hip fracture. This will help you identify what he could do before the injury and set that as the end-goal or at least the focus of your/his direction.
Some simple things you can use to measure activity level might be how far he walks in a day. Purchasing a simple pedometer that counts footsteps will give you a fairly accurate estimation of footsteps. Have your father wear this for a three to five days just to see what his daily distance might be and perhaps get an average over that period of time.
The goal might be to increase the number of steps taken each day by 10 or 20 or 50 paces — whatever seems reasonable and do-able. Don’t set the goal so high that he gets discouraged and gives up. Start with trying to maintain a base level (taking the same number of steps on most days) and build from there. Expect some ups and downs based on level of fatigue, general health, and motivation.
Your father will most likely have been given an exercise program to carry out each day. Here you can set the timer and record the number of minutes it takes him to complete the exercises. Once he knows the program well, he can work to complete all the exercises in less time. When the average time it takes seems steady (i.e., he can’t get them done any faster without losing the benefit of doing them correctly), then start to increase the amount of time he exercises by one or two minutes each day. That will help improve overall physical endurance.
Those are just a few suggestions to get you started. If you see there’s a problem even getting this simple program going, you may need the expertise of a physical therapist to help get him started and keep on target. The rest can be done at home under your watchful eye.