I do surf kayaking all year round, uses abdominal, shoulder muscles and forearms, perfect for keeping fit. Getting thrown around in the wash when the waves are rough uses more energy and is bags of unpredictable fun and exercise. No two days are ever the same so fitness is dependant on how many eskimo rolls are needed to upright oneself depending on choppiness and height of waves depending on where I surf, all good fun, beats doing weight training for staying fit and healthy.