The seven-time Tour de France champion finished 120th of 133 riders Tuesday in the six-day Tour Down Under, his first road stage in three years.
Still, Armstrong said he felt "pretty good, pretty strong" for his first day back at work, although he thought officials were kidding when they told him the opening day of the race was also the easiest.
It was nothing more, they said, than two short hill climbs and a pedal through undulating hill country on the fringe of the wine-growing Barossa Valley outside Adelaide. But the searing heat tested even the fittest riders, almost all of them younger than the 37-year-old cancer survivor.
"It's nice to get one under way and tomorrow's another hard day," Armstrong said. "I want to take it day by day, but I think the early indications are that I feel pretty good, pretty strong."
Germany's Andre Greipel, the winner of last year's race, won the first stage by a bike length in a bunched finish. Taking time bonuses into account, he will carry an 11-second lead into Wednesday's 90-mile second stage. The race ends Sunday.
Armstrong coasted to the finish near the back of the pack. Unfazed by the heat and the day's exertion, the Texan spent 20 minutes talking with Australian Prime Minister Kevin Rudd.
"We've never met," Armstrong said. "So it's an honor not just for myself but for the race to have him here. We talked a little bit about cycling, talked a little bit about health care, talked about the inauguration tonight, talked about the global fight against cancer."
Armstrong found the dry heat sapping but was most at home on the hills, where the 133 cyclists labored on country roads that rose abruptly.
"It's hot, man, it's hot," he said. "It's a dry heat but it effects performance a lot. There's really no way to perform at a high level when it's (103) degrees. You just cope and drink as much as you can. I think we must have gone through maybe 15 or 20 bottles each today."
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