You might want to bring your dumbbells on that next spaceflight.

During space missions lasting six months or longer, astronauts can experience bone loss equivalent to two decades of aging. A year of recovery in Earth’s gravity rebuilds about half of that lost bone strength, researchers report June 30 in Scientific Reports.

Bones “are a living organ,” says Leigh Gabel, an exercise scientist at the University of Calgary in Canada. “They’re alive and active, and they’re constantly remodeling.” But without gravity, bones lose strength.
Gabel and her colleagues tracked 17 astronauts, 14 men and three women with the average age of 47, who spent from four to seven months in space. The team used high-resolution peripheral quantitative computed tomography, or HR-pQCT, which can measure 3-D bone microarchitecture on scales of 61 microns, finer than the thickness of human hair, to image the bone structure of the tibia in the lower leg and the radius in the lower arm. The team took these images at four points in time — before spaceflight, when the astronauts returned from space, and then six months and one year later — and used them to calculate bone strength and density.

Astronauts in space for less than six months were able to regain their preflight bone strength after a year back in Earth’s gravity. But those in space longer had permanent bone loss in their shinbones, or tibias, equivalent to a decade of aging. Their lower-arm bones, or radii, showed almost no loss, likely because these aren’t weight-bearing bones, says Gabel.

Increasing weight lifting exercises in space could help alleviate bone loss, says Steven Boyd, also a Calgary exercise scientist. “A whole bunch of struts and beams all held together give your bone its overall strength,” says Boyd. “Those struts or beams are what we lose in spaceflight.” Once these microscopic tissues called trabeculae are gone, you can’t rebuild them, but you can strengthen the remaining ones, he says. The researchers found the remaining bone thickened upon return to Earth’s gravity.
“With longer spaceflight, we can expect bigger bone loss and probably a bigger problem with recovery,” says physiologist Laurence Vico of the University of Saint-Étienne in France, who was not part of the study. That’s especially concerning given that a crewed future mission to, say, Mars would last at least two years (SN: 7/15/20). She adds that space agencies should also consider other bone health measures, such as nutrition, to reduce bone absorption and increase bone formation (SN: 3/8/05). “It’s probably a cocktail of countermeasure that we will have to find,” Vico says.

Gabel, Boyd and their colleagues hope to gain insight on how spending more than seven months in space affects bones. They are part of a planned NASA project to study the effects of a year in space on more than a dozen body systems. “We really hope that people hit a plateau, that they stop losing bone after a while,” says Boyd.

A flexible electronic implant could one day make pain management a lot more chill.

Created from materials that dissolve in the body, the device encircles nerves with an evaporative cooler. Implanted in rats, the cooler blocked pain signals from zipping up to the brain, bioengineer John Rogers and colleagues report in the July 1 Science.

Though far from ready for human use, a future version could potentially let “patients dial up or down the pain relief they need at any given moment,” says Rogers, of Northwestern University in Evanston, Ill.
Scientists already knew that low temperatures can numb nerves in the body. Think of frozen fingers in the winter, Rogers says. But mimicking this phenomenon with an electronic implant isn’t easy. Nerves are fragile, so scientists need something that gently hugs the tissues. And an ideal implant would be absorbed by the body, so doctors wouldn’t have to remove it.

Made from water-soluble materials, the team’s device features a soft cuff that wraps around a nerve like toilet paper on a roll. Tiny channels snake down its rubbery length. When liquid coolant that’s pumped through the channels evaporates, the process draws heat from the underlying nerve. A temperature sensor helps scientists hit the sweet spot — cold enough to block pain but not too cold to damage the nerve.

The researchers wrapped the implant around a nerve in rats and tested how they responded to having a paw poked. With the nerve cooler switched on, scientists could apply about seven times as much pressure as usual before the animals pulled their paws away. That’s a sign that the rats’ senses had grown sluggish, Rogers says.

He envisions the device being used to treat pain after surgery, rather than chronic pain. The cooler connects to an outside power source and would be tethered to patients like an IV line. They could control the level of pain relief by adjusting the coolant’s flow rate. Such a system might offer targeted relief without the downsides of addictive pain medications like opioids, Rogers suggests (SN: 8/27/19).

Now the researchers want to explore how long they can apply the cooling effect without damaging tissues, Rogers says. In experiments, the longest that they cooled rats’ nerves was for about 15 minutes.

“If treating pain, cooling would have to go on for a much longer period of time,” says Seward Rutkove, a nerve physiologist at Harvard Medical School who wasn’t involved in the study. Still, he adds, the device is “an interesting proof of concept and should definitely be pursued.”