What are physical therapy exercises that can reduce the risk of bedsores?

None. There are no specific exercises that prevent bed sores. Bed sores are caused by pressure on the skin in people who are immobile. When mobile people feel pressure in certain areas of their bodies they move around to alleviate the pressure. In immobile people, they need to be helped to do this by others. Turning a person from side to back to side every 2 hours helps. Special beds can help.
Pressure Ulcers PT. It depends on the location of the pressure ulcers. Physical therapy to strengthen the patient in general is always a wonderful idea but if the ulcerations are on the heels this will prevent further challenges for the patient and the therapist.
Interesting. PT may help indirectly in some patients if it helps improve strength, nutrition and mobility. But in reality, bedsores occur in bed or wheelchairs when patients are immobile. The key is to shift places every one to two hour la to prevent constant pressure on one bony area for too long. For some pts PT can build muscle and help prevent. For most others it will have no effect.