LONGUEUIL, Que. -- During his first days in the microgravity of space, David Saint-Jacques was transported back to his childhood, the Canadian astronaut told reporters Monday.

It was not the feeling of gazing at the heavens in wonder he was talking about but the sensation of hanging upside down at a playground as blood rushes to your head.

"I'm a little bit congested here, like most people are, because the gravity is not there to pull blood down into your legs," Saint-Jacques explained Monday over a video link between the International Space Station and Canadian Space Agency headquarters.

"Your body has to adjust to that, so initially you have kind of a big red puffy face .... Do you remember as a child hanging from the monkey bars in the park, how your head kind of puffs up? That's kind of how you feel constantly initially, and then it normalizes."

The astronaut, who arrived at the International Space Station Dec. 3, said there have already been plenty of breathtaking moments. The first sunrise from orbit after he and fellow astronauts Anne McClain of NASA and Oleg Kononenko of the Russian space agency, Roscosmos, blasted off was "quite an emotional moment," he said.

"I looked out the window and this little blue crescent started to get brighter and brighter and I realized, 'Wow, this is actually the curve of the earth,' " he said. "So that first sunrise on orbit, I will never forget. It was very moving -- just so beautiful."

In his first news conference from the space station, he said he is trying to learn as much as possible from the occupants who have been there since June and are scheduled to return to Earth Dec. 20. They are Serena Aunon-Chancellor of NASA, Alexander Gerst of the European Space Agency and Sergey Prokopyev of Roscosmos.

He said he has begun to "dabble" in Earth photography, including photos of his hometown. Saint-Jacques was born in Quebec City and raised in the Montreal suburb of St-Lambert.

"It is just a never-ending sense of awe looking at our blue planet -- this thin blue line in the atmosphere, that colour, that flash of blue -- it's just unbelievable," he said, adding that he is moved by the beauty of sunrises and sunsets and the sense of Earth's size.

"It's very touching, and it's very humbling, and it makes you want to go back to Earth and help make it better."

Saint-Jacques said nothing in the intensive training astronauts undergo can prepare them for the feeling of weightlessness.

"So I do the typical rookie mistakes, try not to crash anywhere, and my colleagues are showing us how to fly," he said. "The other thing we notice about our bodies, of course, is that you lose a sense of orientation, and initially it's easy to get lost, but we'll get used to it."

Saint-Jacques was playful during his exchange with reporters, spinning his mike in the air and at one point letting it drop and continuing to talk as it floated in place. When the session ended he said goodbye and disappeared up out of the picture.

Aboard the station, the 48-year-old physician will conduct a number of science experiments, with some focusing on the physical effects of the microgravity astronauts experience in orbit and others on how to provide remote medical care.

The last Canadian astronaut to visit the space station was Chris Hadfield, who was on a five-month mission that ended in May 2013.