How Bouncing Workouts Can Boost Bone Density

When NASA prepares astronauts for missions to outer space, improving and monitoring bone density is one of the first things on the agency’s to-do list. That’s because space travel actually accelerates ageing at a cellular level, and without gravity doing its daily work on the skeleton, bone loss can set in fast. The solution? A surprising amount of bouncing.

And, as it turns out, the same biomechanical workout principles that keep astronauts' skeletons mission-ready have plenty to teach those of us on Earth. Repetitive, impact-based movement — think trampolining, rebounding, even skipping — triggers osteoblast activity, the process by which your body actively builds new bone tissue. This is especially important as our bodies age, and can keep our bones from getting brittle and breaking. While that might sound like a niche concern, for certain people, it could be one of the most important things they do for their long-term health. Here's what the science actually says.

The science of gravitational loading and osteoblast activity

Our 206 bones aren’t the passive, inert scaffolding most of us picture when we think of our physiology. Instead, our bone structure is affected by what you do every single day, and is constantly being broken down and rebuilt — a process known as remodelling.

The key players here are special cells called osteoclasts, which resorb old bone, and osteoblasts, which are responsible for laying down new tissue. Using these two cell types, your skeleton doesn't just build indiscriminately, but instead forms and repairs using specialised cells called osteocytes. Within the bone matrix, osteocytes act as the primary load sensors — detecting mechanical strain and translating it into biochemical signals that tell osteoblasts to get to work. Research published in Bone Research found that this mechanical stimulation triggers calcium signalling cascades that directly drive bone formation. Without that load, as studies on microgravity and prolonged bed rest confirm, osteoblast activity drops and bone loss follows. The skeleton, it turns out, only invests in itself when you give it a reason to.

Why your body only builds bone when it's under load

You might be familiar with the concept of muscle building: individual muscle fibres need to be torn and rebuilt in order to become stronger and bigger. The same theory can be applied to building bone strength. “Just like muscle tissue, it needs to break down,” says performance trainer Tom Hall, who has spent years closely studying the relationship between performance biomechanics. “Something needs to break down to be built back stronger,” he continues, “otherwise there's no stimulant.”

One of the most effective ways to build bone strength? Bouncing, or bounding. “High-impact training, jumping or running, creates little points of damage in your bone,” Hall says, which triggers the body to repair and strengthen. Those small stresses “increase osteoblastic cell activity” due to various mechanical strains that occur during the exercises. So how does it actually work, and is it comparable to other sports? 

How rebounding compares to running, lifting and HIIT

Bone is living tissue and like most living things, it responds to what you ask of it. Bouncing, whether that's skipping, jump drills, or controlled rebounding, works as a result of the speed of the load, not just the load itself. "That quick change in force creates tiny, safe amounts of bending within bone and osteocytes act like the skeleton's strain sensors," says Dr. Shelby Marquardt. When those sensors detect strain, they reduce sclerostin and activate bone-forming pathways. What matters, Dr. Marquardt says, is that "bones respond particularly well to short bouts of higher strain rate work, rather than only long, steady efforts." This is partly why a brisk skipping session can be more osteogenic than a long, steady run.

When we compare bouncing and bounding to running, however, Hall explains that the different disciplines are still very comparable, due to the amount of force that’s produced during sprints or single-leg bounds. “When somebody's doing a triple jump, for example, they’re putting between 15 to over 22 times your body weight through a single leg,” Hall says. “A 100kg male, bounding at full force, is putting 22 times their body weight through one limb.” As for running, Hall estimates it at around five to 13 times your bodyweight. For HIIT, however, the comparisons are negligible. “You're not doing HIIT to get stronger, or for bone mineral density,” he continues. “HIIT would be more for cardiac health than for skeletal health.” 

Who can benefit most?

Although much of the relevant research on high-impact and resistance-based bouncing exercise focuses on post-menopausal women, who often show the greatest improvements in bone health, the same principles also apply earlier in life, per Hall.

Studies show that high-impact loading through activities like bounding and plyometric work improves bone mineral density in premenopausal women, and that exercise actually has its maximum effect on bone when performed at a younger age. Younger women in their 20s and 30s — arguably the peak bone-building window — who regularly do appropriately-loaded bounding and jumping exercises alongside resistance work, often benefit most in terms of building bone density, thereby reducing their future risk of osteoporosis and osteopenia.

What a bone-building bounce routine actually looks like

As with many things that require time, effort, and a deliberate attempt at change, Hall’s advice is to start “little and often.” He points to box jumps — a plyometric exercise where you jump from a standing position onto an elevated box or platform. He emphasises the importance of the technical landing phase of the movement, in which you hold a stable, motionless stance. Hall explains: “you jump, then 'stick' in what is essentially an athletic position, like a quarter squat,” he says. “Land in that pause, count to three and then go again.” It’s here that the magic happens, Hall says. “That little pause is really important, as when your body weight is going down, you get that ‘stick’ happening and the force the floor is pushing back into you needs to stay there.” 

By sticking, Hall says, “that energy goes into you instead of dissipating”, and by using a countermovement jump, “you're using elastic properties” — both two fundamental parts of building more resilient bone strength. 

Other exercises Hall recommends include squat jumps, broad jumps, and plyometric movements like pogo hops. Shoot for 8 to 10 reps of each, working for no more than 20 seconds each time, he says — and make sure you have enough time to recover in between. “You don't want more than like 40 or 50 jumps in one session,” he advises.

The nutrients that make the work pay off

You can do all the right movements and still undercut yourself at the dinner table. Dr. Marquardt's starting points are calcium (around 700mg a day) and vitamin D (at 10 micrograms a day), to support absorption. It's also worth supplementing through autumn and winter if you're in the UK, focusing on getting Vitamin K from leafy greens and magnesium from nuts, seeds and wholegrains. The factor most people miss, she says, is simply eating enough overall — "chronic under-fuelling can impair bone remodelling," which is something we could all do with remembering. 

Could Slower Workouts Be The Secret To Lower Inflammation?

Read more

Read more

What To Drink Before, During And After A Workout

Read more