If your legs are in good shape here's a basic program to add strength to those legs. If your not in such good shape or you've had serious leg injuries talk to your doc and PT for more information on implementing a lower leg strengthening program.
Week One: (5 days on, 2 days off)
Add jump rope (3-5 minutes)
Add unweighted squats - 4 sets of 25
Add unweighted calf raises - 4 sets of 25
Week two: (5 days on, 2 days off)
Jump rope (5 minutes)
Unweighted squats - 3 sets of 25
Unweighted calf raises - 3 sets of 25
Add Unweighted lunges - 3 sets of 15 each leg
Week three: (5 days on, 2 days off)
Jump rope (5 minutes)
Unweighted squats - 1 set of 100
Unweighted calf raises - 1 set of 100
Unweighted lunges at angles - 3 sets of 15 each leg
Week 4-6:
**(5 days on, 2 days off)**
Jump rope (5 minutes)
Unweighted squats - 1 set of 25
Unweighted calf raises - 1 set of 50
Unweighted lunges at angles - 1 sets of 15 each leg
**(1 day on, 2 days off)**
Bike ride for 12 minutes
Squats - 3 sets of 12
Calf raises - 3 sets of 12
Lunges - 3 sets of 12
This routine should allow you to try pylometric jumps which should help you reach your potential at this time in your life. I would not suggest doing pylometric training for more than 4 weeks in a row, at 40 two weeks should be sufficient to see a gain. For more on Pylometrics see local library and that way you can tailor a program for your specific needs.
Have fun with it.