Hence, our goal was to develop new protocols to speed nitrogen elimination during pre-breathe by combining oxygen breathing with controlled exercise. (Adding exercise into the equation increases the blood flow, which results in a faster nitrogen washout, but too much or too aggressive exercise can promote bubble formation and increase risk—this is the dualism of exercise).

"The same principle regarding blood flow actually applies to divers as well, but again careful thought must be applied. If a diver exercises whilst descending or at depth, the inert gas absorption will be accelerated, effectively increasing the decompression obligation. A diver who does light exercise during decompression will accelerate inert gas elimination
from his or her tissues, just like an astronaut who breathes oxygen.

Too much exercise during decompression, however, can increase bubble formation and the risk of decompression insult, so caution must be employed. This is definitely not a case of 'if a little is good, more is better'—'more' can get you into trouble, and there is no simple way to optimize strategies."

A multi-center team developed and tested four protocols initially, resulting in the first protocol approved for flight (and a previous NASA award). The team included research groups from NASA Johnson Space Center, Duke University, University of Texas at Houston and the Defence and Civil Institute of Environmental Medicine [DCIEM] in Canada, and consultants
from the U.S. Air Force. Duke subsequently took the lead in testing five more protocols, with one of these also approved for flight.

"We were all delighted that the new prebreathe protocol, known as 'ISLE' (in-suit light exercise) worked successfully when it was tested in orbit during the STS-134 / ULF6 mission.”

It was this success that resulted in the current award. “This has very much been a team effort, and it’s been a long project,” stated Vann. “The genesis of this concept came about in the 1980s.

"I agree that exercising in space sounds quite straight forward to most people, but it does come with its own set of special challenges. The first operational trials by NASA took place during the shuttle missions when astronauts used exercise equipment whilst breathing oxygen. The equipment was complicated since it had to be built to avoid transmitting vibrations into the spacecraft during use. Ultimately, a simple cycle ergometer became a very complication 'CEVIS' (cycle ergometer vibration isolation system).

The complexity proved to be logistically cumbersome, failing several times on orbit. Therefore, our next task was to develop a protocol that didn’t involve extra equipment. The logical step was for the astronauts to exercise whilst breathing oxygen in the space suit.

"The effect of gravity on Earth is our normal reference standard for exercise. After we lift a leg up, it falls back naturally. In space in zero gravity, when we lift a leg it keeps on moving. So, exercise in microgravity is different. The astronaut must be anchored to the wall, and then work to initiate limb movement, to stop it at the end of the movement range, and to initiate movement in a new direction.”