Most people are physically capable to enjoy one of these paddlesports. The sport that will leave the least physical impact is rafting, since it only involves a few basic paddle strokes. However, some runs are more intense than others depending on the Class of whitewater. Higher class, more intense, whitewater can cause a great deal of stress and anxiety to people who are not prepared.
If you are unsure whether or not you are capable of participating in these sports, ask your doctor.
Also please be sure that you know how to swim! It is quite common that people who aren’t strong swimmers or just plain don’t know how to swim participate in these sports—and they end up in trouble. Go get some practice before attempting to participate.