Flareups sometimes kept her from exercising for weeks at a time, she said.
Castle said she has never let her ailments squash her effort to keep her body - her heart especially - as fit as possible.
Now, she hopes to convince others they can do the same through an aerobics video aimed at people with health conditions.
"There's a lot of people out there that have ailments that think they can't do exercise. They don't know where to start," said Castle, who believes her lifelong commitment to exercise has helped keep her health problems in check.
In the 19 years she has been teaching aerobic classes, Castle said she always has tried to stick to the basics, showing her students how to move correctly to keep from stressing their backs and joints.
As long as they're not hurting themselves, Castle said, she encourages students to modify their routines to a level at which they're comfortable.
"It depends on what you want to do for yourself," she said.
For example, one of her regulars - a 74-year-old woman with asthma - does her own less-strenuous variation of the leg lunges portion of the class.
If things go as she hopes, Castle will be able to reach others like her all over the country through the small screen.
The idea for the special video came from a student, who complained that a video she had tried didn't give her as good a workout as Castle's class.
Castle said she would like her video to be an hour long, so she can include a thermal warm-up, aerobic workout, cool down, floor work and stretching.
The length will depend on how much backing she can find for the project, said Castle, who said she was quoted $1,000 per minute by one professional video producer.
She said she's looking into the possibility of getting a class at Hagerstown Junior College to take on the project.