The link between crocodile blood and performance is not such a strange one, because scientists have marveled for years at the ability of crocodiles to remain underwater for over an hour without a single gulp of fresh air. The crocodiles' requirement for fresh supplies of oxygen is so low that the scaly beasts sometimes simply drag their prey under water, drowning their unfortunate victims without the need for a killing crunch of their powerful jaws. Strangely enough, crocodiles can stay underwater for long periods of time even though their tissues have very low levels of myoglobin, a unique protein which stores oxygen and permits other animals such as whales and seals to remain in the briny deep for extended periods.

The crocodiles' low-oxygen performances can occur because the oxygen-carrying protein in their blood, haemoglobin, functions in a very unique way. What happens is that as crocodiles hold their breath under water, carbon dioxide builds up in their blood to high levels. This carbon dioxide dissolves and forms bicarbonate ions.

These bicarbonate ions immediately latch onto a section of the crocodiles' haemoglobin molecules, forcing the haemoglobin to release its attached oxygen. This oxygen can then rush into the tssues, making it unnecessary for the underwater reptiles to rise to the surface.

This effect could be a great advantage for human athletes with crocodile haemoglobin inserted into their red-blood cells (human haemoglobin lacks the key crocodilean amino acids which have a bicarbonate affinity). As such athletes exercised vigorously, the surplus bicarbonate automatically produced would attach to the croc haemoglobin and 'push' extra oxygen into the muscles, providing extra energy and increasing endurance. Instead of sputtering at oxygen-limiting intensities, human athletes with crocodile haemoglobin would 'eat up' their opponents.

Ingeniously, the Cambridge scientists were able to determine the exact docking spot' on crocodile haemoglobin for bicarbonate. They then coaxed bacterial cells into producing extra copies of these attachment points and transplanted them into human haemoglobin. Basically, the scientists had produced a completely new type of haemoglobin - part human, part crocodile - which would be very effective at releasing oxygen into human tissues.

In a medical setting, this new haemoglobin would be a boon to patients who have problems getting enough oxygen to their tissues (people suffering from emphysema might benefit greatly). In the athletic arena, the hybrid haemoglobin might help athletes perform for longer periods of time at high exercise intensities. The world scoffed when Ma Junren added turtles' blood to the diets of his athletes, but a bit of crocodile blood, inserted into human haemoglobin, could probably produce truly peak performances. ('Transplanting A Unique Allosteric Effect from Crocodile into Human Haemoglobin,' Nature, vol. 373, pp. 244-246, 1995).