Path of greatest resistance could help limit astronauts’ bone loss

(ORDO NEWS) — Astronauts returning from three months of spaceflight may show signs of incomplete bone recovery even after one year on Earth, but adding resistance exercise during spaceflight can help limit bone loss.

A small study on 17 international astronauts showed that although the lower leg bone partially regenerates, sustained bone loss after one year is equivalent to ten years of normal age-related bone loss on Earth.

Stephen Boyd and his colleagues took pictures of 17 astronauts (14 men and three women) before space flight, after returning to Earth, and also six and 12 months after recovery.

They scanned the bones of the lower leg (tibia) and radius (forearm) to calculate their resistance to fracture (fracture load), bone mineral content, and tissue thickness.

The authors also added exercises such as cycling, running on a treadmill, and bench press that the astronauts performed during and after the flight.

A year after the flight, the average results in 16 astronauts showed incomplete restoration of the bones of the lower leg.

The median tibial fracture load, which measures bone strength, decreased by 152.0 Newtons. The forearm performance of all astronauts did not differ after 12 months of recovery compared to the pre-flight level.

The researchers noted that astronauts who had missions longer than six months (eight astronauts in total) experienced significantly less bone recovery.

For cosmonauts who were on missions for more than six months, the average load of destruction of the bones of the lower leg after a year decreased by 333.9 Newtons compared to the pre-flight period, while for astronauts who were on missions for less than six months (nine cosmonauts), the load of destruction decreased at 79.9 newtons.

Similar differences were found for the total bone mineral density in the lower leg. Overall, in nine astronauts (seven of them from long missions), the total bone mineral density of the lower leg did not fully recover after 12 months.

Among all astronauts, those who completed more in-flight bench press workouts compared to their individual pre-flight workouts were identified among those who regained calf bone mineral density.

The scientists suggest that, along with currently used physical exercises, resistance jumping exercises, which provide high-impact dynamic loads to the legs, may help prevent bone loss and promote bone formation during space flights.

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