This blog explores how space travel research reveals effective strategies for improving bone density on Earth. It explains how mechanical loading affects bone health and why resistance training is essential as we age. Drawing inspiration from astronaut training protocols, it highlights practical ways to apply progressive strength exercises and impact-based movements to maintain strong bones. Physical therapy plays a key role in guiding safe and effective programs.
Following the 10 day Artemis II mission has been a balm and a beacon of hope in an extremely difficult year of news. It culminated with me watching the Friday night, prime time splashdown in awe. And then a weekend IG feed full of astronaut and Mission Specialist, Christina Koch. I’m not mad about it.
I’ve always been a sci-fi geek.
I grew up reading Heinlein and Bradbury. Later when I got a bit older, Octavia Butler. I watched, and continue to watch, Star Trek. These stories have consistently championed adventure, curiosity, acceptance of those who are different, teamwork, camaraderie, and deep mutual trust.
The space crew and leadership teams on the Artemis II are no exception. Today as I write this, I’m focusing on the positive. What a time to be alive when we can see such wonder and human excellence playing out in real life!
It’s got me thinking about bones. Human bones. Bones in space and bones on Earth.
I think about bones a lot.
Imagine floating in the International Space Station, watching Earth drift by, free of gravity’s pull. Sounds dreamy. But then you learn that without gravity, astronauts can lose 1–2% bone mass each month. Back on Earth, aging steals bone more slowly but no less importantly.
Here’s the good news: The exercise strategies developed to protect astronauts’ skeletons in microgravity give us powerful insight into keeping our bones strong as we get older. Here’s what space science teaches us about resistance training for bone health, and how to best apply it here on Earth.
Why bones weaken: Space vs. aging (same problem, different speed)
Bones are living tissue that depend on mechanical stress to stay strong. When bones are loaded (think bodyweight + gravity and the addition of external loading forces on an upright, standing skeleton) they respond by building more bone. Remove that load and bone-resorbing cells outpace bone-building cells. Bone mass declines.
- In space, microgravity removes almost all weight-bearing loads. The skeleton essentially “forgets” it needs to be strong, so bone loss happens quickly. Bone loss affects the entire skeleton, but more so in the major weight-bearing body regions such as the femur (thigh bone), hip, and spine.
- On Earth, aging causes a slower but steady decline. Decreased activity due to lifestyle changes in middle age, poor eating habits, fragmented sleep, and chronic disease processes tilt the balance toward bone loss.
The shared lesson: Insufficient mechanical loading is a key driver of bone loss, whether it happens in weeks on the ISS or over decades in our Earthly bodies.
What works in space: Frequent, heavy loading
NASA and space medicine teams have engineered solutions for mitigating bone loss in microgravity. Astronauts use specialized resistance training equipment to mimic the forces bones normally experience on Earth.
On the ISS they use devices like ARED (Advanced Resistive Exercise Device) to replicate squats, deadlifts, and presses without gravity.
Check out this video on the ISS and astronaut Jessica Meir’s Instagram page for a glimpse into how the ARED functions, and other pieces of equipment used for cardio conditioning in space.
A squat rack in space, y’all. Totally rad.
When astronauts follow these programs, bone loss is reduced or even prevented. That success points to practical lessons for anyone concerned about bone health here on Earth.
Translating space bone-building strategies to aging bones on Earth
The principles in both environments are straightforward, accessible, and actionable.
Prioritize progressive, load-bearing resistance training.
- Aim for 2–3 sessions per week of full-body strength work. Focus on standing, multi-joint movements that load the hips, spine, and legs: Squats/box squats, deadlifts, lunges, step-ups, rows, and presses.
- Use progressive overload: Gradually increase the weight, reps, or difficulty so exercises remain challenging. Effort near muscular fatigue stimulates meaningful bone response.
- While of course not as extreme as life in microgravity, modalities like walking, yoga, Pilates, swimming, and cycling do little to support bone growth. You’ll get the best bone-building bang for your buck with resistance exercises (adding external forces that are heavier than your bodyweight and gravity alone) and doing those exercises standing up.
- Read more here about bone building strategies on Earth to combat osteoporosis: Weight Lifting for Bone Density
Add impact or impact-mimicking activities if appropriate.
- Short, controlled bursts of impact (jumping, hopping, weighted step-downs) have been shown to stimulate bone, especially in the hips and spine. For many older adults, lower-impact options that still create quick force—like rapid weighted step-downs, medicine ball slams, or moving light to moderate weight with speed—are good options.
Strength and power training improve balance and decrease the risk of falling.
- Decreased bone mass all by itself won’t hurt you. Falling and sustaining a fracture will.
- Placing an emphasis on the two methods described above, resistance training and power (moving with speed), in an upright weight-bearing position improves muscle reaction times and decreases the risk of falling.
Pair exercise with bone-supporting nutrition and health care.
- Aim for adequate protein intake (roughly 20–30 g per meal for older adults), and sufficient daily calories for your level of activity.
- Review medications with your clinician as some drugs affect bone health.
- Get appropriate screening (DEXA scans when recommended) and medical clearance before starting an intense program if you have osteoporosis, recent fractures, or conditions that affect cardio-respiratory function, metabolic health, or nutrient absorption.
What the research evidence says about resistance training to combat bone loss (in space or on Earth)
Clinical trials show that combined resistance and impact training can preserve or even increase bone mineral density (BMD) in older adults, especially at loaded sites like the hip and spine.
Effect sizes vary by program, intensity, and participant health, and bones take time to change. Expect measurable improvements over months to years, not overnight.
Exercise reduces fracture risk through multiple pathways: Stronger muscles, better balance, fewer falls, and over time, tougher bones.
Stay consistent. Track your weights. Progress slowly and steadily.
It’s inspiring to think that solving a problem in an extreme environment like space can teach us practical ways to live better, healthier lives on Earth. Astronauts’ resistance programs show us that even when gravity is absent, we can engineer forces to keep bones healthy and strong.
On our home planet, we can use those same principles: Challenge the skeleton with load-bearing forces, eat well, and build balance and strength to stay active and independent for decades to come.
Small, consistent steps: A heavier squat, an extra rep or two, an extra set of exercises in the week. They all add up.
Gravity is on our side. Let’s use it!
Ready to get started? Talk with your healthcare provider or come in for an evaluation with one of our physical therapists specializing in resistance training for bone health. We also offer in-person small group strength classes so you can get individualized support in a fun social environment.
1. Physical Therapy for Osteoporosis and Osteopenia
If you are local to New York City (Nomad, Flatiron, and Chelsea neighborhoods), come see me for physical therapy. I’ll conduct a thorough clinical examination that covers whole-system health factors as they relate to common musculoskeletal complaints in menopause and post-menopause, a movement screen and physical exam, as well as advice for implementing a strength training program to prevent and treat osteoporosis. Practice Human proudly accepts Medicare and works out-of-network with most insurance plans.
2. Small Group In-Person Strength Classes for Women with Osteoporosis
For those local to New York City (Nomad, Flatiron, and Chelsea neighborhoods), Durability for Life is Practice Human’s signature small group strength training course. Designed for women ages 65+ who want to feel more confident and capable in daily life and with more demanding physical activity. Appropriate for people with osteopenia, osteoporosis, knee and hip arthritis, and persistent low back pain. Led by physical therapist and strength & conditioning coach Caitlin Casella.
Next on your reading list: Weight Lifting for Bone Density
