I met a woman earlier this year who exemplifies this. She had chronic fatigue syndrome, but something in her told her to go to yoga. She did not have the energy to do any of the poses or to even sit upright, so she slept through each class. I'll repeat that: she slept through each class. FOR. A. YEAR. She said that the other students thought she was crazy, but she kept going because she believed she was benefitting from being in that environment and from the mantra music. She began to get better. She began to participate in the classes. She became so impressed with the healing benefits that she did her teacher training, and today she is a fully vital and healed Kundalini Yoga teacher.
There's always a way and there's always a benefit -- even if you can't sit upright.