When planning a Nitrox dive, why is it essential to consider individual fitness levels?

Considering individual fitness levels when planning a Nitrox dive is crucial because fitness can significantly impact how the body absorbs and off-gases nitrogen. A diver's physical condition affects circulation and the efficiency of the respiratory system, which in turn influences nitrogen uptake in body tissues during the dive and the rate at which nitrogen is eliminated after the dive. Divers who are more physically fit may have a more efficient cardiovascular system, possibly allowing for better nitrogen metabolism and faster off-gassing. Additionally, fitness levels can influence how well a diver manages physical exertion underwater, which also plays a role in gas uptake. This understanding of individual fitness levels helps ensure a safer diving experience by mitigating risks associated with nitrogen narcosis and decompression sickness.