An 85-year-old man recently won a slip-and-fall case against supermarket superstore Safeway. The man slipped in liquid laundry detergent left in one of the aisles of the store. The injury was severe, a broken femur that required surgery and insertion of a medical rod. The victim has required repeated rehabilitation sessions and continued physical therapy and may never fully regain use of his leg.
Yoga is often touted as a "feel good" type of exercise that virtually anybody at any level of fitness can do. It's low-impact, so it isn't likely to stress your knees. It isn't aerobic, so it doesn't require people to have a strong heart or lungs. It doesn't take any machinery to do, so you don't have to worry about falling off (like you might a treadmill or stair machine).
We think of crashes as one vehicle colliding with another. A route to compensation is clear. The injured party files a claim against the driver who caused the accident.