Dinosaur activity has been the object of speculation since the first skeletal reconstructions were completed in the last century. Charles Knight, the famous artist, painted dinosaurs as active agile animals whereas researchers later portrayed them as slow moving and clumsy due to some similarities with modern reptiles. Modern research leans toward an active lifestyle for such enormous animals. This implies that dinosaurs needed a lot of oxygen to supply the necessary energy for these activities, but is it possible to estimate just how much this really was? Modern investigations confirm that the ability to supply oxygen to active tissues such as muscle is the factor most likely to set the limits of performance.