These exercises may help astronauts get their knees space ready

By Stephen Beech

Jumping workouts could help astronauts prevent cartilage damage they are likely to suffer during lengthy missions to Mars, suggests new research.

The first study of its kind shows knee cartilage in mice grew healthier following jumping exercises.

The American research adds to ongoing efforts by space agencies to protect astronauts from getting out of shape due to low gravity - a key aspect of their ability to perform spacewalks, handle equipment and repairs, and conduct other physically demanding tasks.

Study author Dr. Marco Chiaberge said: “Since the next step in human exploration of space is going to Mars and spending long periods of time in permanent bases on the moon, cartilage damage is a really major issue that space agencies need to address despite how very poorly understood it is.

“The positive effect we saw in these mice is huge, and the magnitude of it was unexpected.

"They can basically make their cartilage thicker if they jump. Maybe astronauts could use similar training before their flight as a preventive measure.”

Dr. Chiaberge, an astrophysicist at Johns Hopkins University in Baltimore, explained that healthy cartilage is essential for pain-free movement, as it cushions joints and decreases bone friction.

But cartilage heals slowly and does not regenerate as fast as other tissue.

Prolonged periods of inactivity - whether as a result of bed rest, injury, or space travel - can accelerate cartilage breakdown.

Dr. Chiaberge says space radiation can also accelerate this effect, and European Space Agency (ESA) experiments have shown evidence of cartilage degradation in astronauts who spend several months aboard the International Space Station.

He said: “Think about sending somebody on a trip to Mars, they get there and they can't walk because they developed osteoarthritis of the knees or the hips and their joints don't function.

“Astronauts also perform spacewalks often. They serviced the Hubble Space Telescope five times, and in the future, they will need to spend more time in space and on the Moon, where we will build larger telescopes to explore the universe and where they will need to stay as healthy as possible."

Previous research has shown that treadmill running may help slow cartilage breakdown in rodents.

The new Johns Hopkins study, published in the journal npj Microgravity, adds to the evidence by showing that jump-based exercise may prevent articular cartilage loss in knees and could actually improve cartilage health.

The research team found that mice in a nine-week program,e of reduced movement experienced cartilage thinning and cellular clustering, both early indicators of arthritis.

However, mice that performed jump training three times a week showed the opposite effect - thicker, healthier cartilage with normal cellular structure.

The study also found the mice with reduced movement had a 14% reduction in cartilage thickness, while those in the jump-training group had a 26% increase compared to the control group.

The jumping mice also had 110% thicker cartilage than the reduced activity group, and jumping also enhanced bone strength.

The researchers found shin bones in the jumping mice had 15% higher mineral density.

Trabecular bone - spongy bone tissue that absorbs impact - was "significantly" thicker and more robust.

Co-author Professor Mark Shelhamer, of Johns Hopkins School of Medicine, said: “Leg strength is particularly important and most highly impacted by microgravity, so any procedures that can address multiple aspects of muscle deconditioning, and maybe even reduce the two-hour daily exercise requirement in space, would be most welcome."

Shelhamer, former NASA Human Research Program Chief Scientist, added: “The same reasoning applies to bone integrity, including cartilage.

"There is increasing recognition of the importance of cartilage as a distinct component in bone integrity, and this study contributes to that understanding.”

While more research is needed to confirm whether humans would enjoy the same benefits, the research team says their findings offer "promising" information to protect cartilage and bone structure.

They say jumping exercises could be included in pre-flight routines to prepare joints for space travel, and specially designed exercise machines could help integrate similar workouts in space.

Co-author Dr. Chen-Ming Fan, a musculoskeletal biologist at Carnegie Science, believes the study could help scientists explore how jump-based training might not only aid patients with arthritis but also boost cartilage health with generally applicable exercises,

The team emphasized the need for further research to determine the ideal exercise volume and frequency for preserving and strengthening cartilage.

They said future work will also explore whether jump training could help reverse cartilage loss and whether the exercise could help astronauts restrengthen their cartilage and recover damage from space flight.

Dr. Fan, who is also an Adjunct Professor at Johns Hopkins, said: “Now that we got our first clue that one type of exercise can increase cartilage, which was completely unknown before, we could start looking into other types of cartilage. What about the meniscus? Could it also get thicker?”

He added: “This research could help performance-enhancement studies, rather than just focusing on pathological conditions, and help athletes or virtually anyone interested in doing the right exercises to improve their performance.”