In terms of design, Neil Armstrong’s iconic 1969 space suit wasn’t exactly optimal. Bulky and stiff, the suit made it pretty hard for the astronauts aboard Apollo 11 to walk around. So, the fact that Armstrong and Buzz Aldrin’s most iconic moments also happen to make them look like they’re float-bouncing across the Moon’s surface is actually the product of their equipment — not the Moon’s low gravity.

Yet, despite knowing how restrictive the space suit was during the moon landing, we’ve spent the last 40 years without ever testing just how fast astronauts can get around on the Moon. Thankfully, a group of NASA scientists have finally looked into the question. And, according to the study they published today in the Journal of Experimental Biology, humans can run a lot faster in lunar gravity than anyone ever expected.

In the study, researchers took eight study participants — three of which were actual astronauts — on a trip aboard NASA’s DC-9 aircraft, a plane capable of reducing its internal gravity to that of the moon during swooping, parabolic flights. There, the astronauts were asked to run on a treadmill during 20 second-long dips at lunar gravity.

Credit: NASA

John De Witt, senior biomechanist at the NASA Johnson Space Center and a study co-author, told a reporter at the Journal of Experimental Biology that the experiment wasn't exactly pleasant for the eight participants. "If you get sick you're done... We wanted to be sure we had people that were used to flying." Still, it appears that they made it through with flying colors.

According to NASA's theoretical calculations, the test subjects should have had an average walk-to-run transition speed of about 1.8 miles per hour (that's compared with transition speeds of 4.5 miles per hour here on Earth). But in the real-life setting offered by the DC-9 aircraft, things turned out differently: the participants' average transition speed was actually 3.13 miles per hour — a speed that's much closer to those we see on Earth.

Credit: NASA

So why were NASA’s theoretical calculations off-base? De Witt thinks the forces generated by the counter-swinging movement of the runners' arms and legs gave them a boost. That force probably exist on Earth as well, he said, but because Earth’s gravity is far stronger, the effect is too small to notice.

Credit: NASA