Scientists at the University of Calgary and elsewhere have tracked 17 astronauts on the International Space Station before and after spaceflight over the past seven years to understand whether the bone recovers after a “long-haul” space flight “. Their results show that, although the bone partially recovers after flight, sustained losses account for at least a decade of normal age-related bone loss, which can advance the onset of osteoporosis.
Gabel et al. examined bone strength, density, and microarchitecture in seventeen astronauts using high-resolution peripheral quantitative computed tomography. Image credit: NASA.
“The detrimental effect of spaceflight on skeletal tissue can be profound,” wrote lead author Dr. Steven Boyd of the University of Calgary and colleagues.
“Decreases in the mechanical load of microgravity cause a substantial loss of bone mineral density and the strength and deterioration of trabecular microarchitecture.”
“Biochemical studies of bone renewal show altered bone metabolism during space flight, so biomarkers of bone resorption increase during space flight, while biomarkers of bone formation are delayed, resulting in a net bone loss “.
“Recovering mineral density and bone strength by returning to Earth’s gravity is a long process, and the bones of many astronauts are never fully recovered,” they added.
“Determining who is most at risk for incomplete recovery of bone tissue is important to understanding the viability of missions beyond low Earth orbit.”
“The primary objective of our study was to use high-resolution peripheral quantitative computed tomography to examine the recovery of bone microarchitecture, density, and strength after a long-term space flight.”
The prospective study included 17 astronauts (14 men and 3 women; average age: 47 years; height: 177.7 cm; body mass: 79.1 kg) from NASA, the Canadian Space Agency (CSA), l ‘European Space Agency (ESA) and Japan Aerospace. Exploration Agency (JAXA) who were selected for missions on the International Space Station (ISS).
The authors made images of the participants before space flight, on return to Earth, and after six to 12 months of recovery.
They performed bone scans on the tibia (cantilla) and radius (forearm) to calculate the resistance of the bone to fracture (failure load), the bone mineral in the bone tissue, and the thickness of the tissue.
They also recorded exercises such as cycling, treadmill running and deadlift performed by astronauts during and after the flight.
One year after the flight, the average results of 16 of the astronauts showed an incomplete recovery of the spinal cord.
The mean spinal failure load, measuring bone strength, was reduced by 152.0 newtons (N) from 10,579 N before flight to 10,427 N after one year.
Total bone mineral density was reduced by 4.5 mg / cm3 compared to pre-flight levels of 326.8 mg / cm3.
Forearm measurements in all astronauts did not differ in 12-month recovery compared to pre-flight.
The researchers observed that astronauts on missions longer than six months (a total of eight astronauts) had a substantially lower bone recovery.
In astronauts on missions longer than six months, the average spinal failure load was reduced by 333.9 N after one year compared to the preflight, while in astronauts on missions less than six months (nine astronauts) the fault load was reduced by 79.9 N.
Similar differences were found for total bone mineral density in the spinal cord.
In all, nine of the astronauts (seven long missions) did not fully recover their total spinal bone mineral density after 12 months.
Of all the astronauts, those who completed a greater amount of deadweight training during the flight, in relation to their individual pre-flight training, were identified as part of those who recovered the bone mineral density of the flight. tibia.
“In addition to the exercise routines currently in use, a jump-resistance-based exercise that provides high-impact dynamic loads to the legs can help prevent bone loss and promote bone formation in the legs. space flight missions, “the scientists said.
His article was published on June 30, 2022 in the journal Scientific Reports.
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L. Gabel et al. 2022. Incomplete recovery of bone strength and trabecular microarchitecture in the distal tibia 1 year after the return of a long-duration space flight. Sci Rep 12, 9446; doi: 10.1038 / s41598-022-13461-1