Australian cyclist Bradley McGee may require more tests before doctors can determine exactly what drained him of all energy in last month's Tour de France.

After wearing the leader's yellow jersey for three days early in the Tour, McGee began suffering inexplicable attacks in the mountain stages which he said made him feel legless for up to 90 minutes.

He was forced out of the current world track championships in Stuttgart to undergo the tests.

At the time it was suspected to be hypoglycemia or a bad reaction to some food, but results from tests taken in Paris on Wednesday will not be known for at least a week.

Doctors told McGee the condition was not serious.

They feel it may be an enzyme problem but might have to take more blood from McGee while he's suffering an attack so they can properly measure the imbalance.

"The professor said I might have to go out on a training ride and have someone behind me so they can collect blood when I have an attack," McGee said.

"It only comes on at the height of exertion."

Although the tests required him to be off the bike for three days and forced him to forgo defending his individual pursuit gold medal on the track, he will be back in the saddle in Hamburg.

McGee will join his Australian FDJeaux.com teammates Baden Cooke and Matthew Wilson in the Huw Classic road race at the Hamburg leg of the World Cup.

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