Is exercise an end or the tool for PD?

http://forum.parkinson.org/forum/viewtopic.php?p=13506#13506

Parkinson's Disease: Exercise and Parkinson's Disease
Because Parkinson's disease affects your ability to move, exercise helps to keep muscles strong and improve flexibility and mobility. Exercise will not stop Parkinson’s disease from progressing; but, it will improve your balance and it can prevent joint stiffening.
You should check with your doctor before beginning any exercise program. Your doctor may make recommendations about:
The types of exercise best suited to you and those which you should avoid
The intensity of the workout (how hard you should be working)
The duration of your workout and any physical limitations
Referrals to other professionals, such as a physical therapist who can help you create your own personal exercise program
The type of exercise that works best for you depends on your symptoms, fitness level, and overall health. Generally, exercises that stretch the limbs through the full range of motion are encouraged.
Here are some tips to keep in mind when exercising.
Always warm-up before beginning your exercise routine and cool down at the end.
If you plan to workout for 30 minutes, start with 10-minute sessions and work your way up.
Exercise your facial muscles, jaw, and voice when possible: Sing or read aloud, exaggerating your lip movements. Make faces in the mirror. Chew food vigorously.
Try water exercise, such as aquarobics. These are often easier on the joints and require less balance.
Work out in a safe environment; avoid slippery floors, poor lighting, throw rugs, and other potential dangers.
If you have difficulty balancing, exercise within reach of a grab bar or rail. If you have trouble standing or getting up, try exercising in bed rather than on the floor or an exercise mat.
If at any time you feel sick or you begin to hurt, stop.
Select a hobby or activity you enjoy and stick with it. Some suggestions include: Gardening; Walking; Swimming; Water aerobics; Yoga; Tai chi.
Reviewed by the doctors at The Cleveland Clinic Neuroscience