About – Castle Flexx


CastleFlexx is a collection of groundbreaking devices that address the ROOT cause of chronic pain issues millions of people face daily across the United States… and globally.

Created by Dan Castle, the former Managing Director of Martha Stewart who left his high-profile role as Martha’s Head of Business and Partnerships so that he could take personal time to address his own health issues.

The first device launched in 2021, The CastleFlexx, and is used by pro athletes across almost every major sport including Olympians, pro team doctors, chiros and physical therapists (Castleflexx has never paid a pro athlete to endorse the product, all posts and reviews are organic and the devices were purchased by the teams and celebrities that use, swear by it and post about it).

The device is highly rated, was reviewed in depth by Oxygen, The Daily Beast and In Touch Weekly- and they each say it actually works.

CastleFlexx has two ISSUED design and utility patents with the USPTO, is made of 100% eco-friendly premium materials and the Atlanta Braves approved it for their home and away games including the 2021 World Series.

meet the founder


“I was always an athlete as a kid and my health was always important to me because I saw how slowly my grandmother passed away over many years in agony with type 2 diabetes. So I played soccer, hockey and after college practiced MMA religiously. One day I was thrown to the mat from a few feet above the ground and my back snapped. A year later I dislocated my shoulder playing in an alumni high-school hockey game. The MRI showed two herniated discs, L4 & L5. The open shoulder surgery resulted in an upper body imbalance that caused extra strain on my lower back and posture (took me ten years to figure this out thanks to Dr Skolnick who is now the chiro for the biggest CEOs in NYC as well as The Juilliard School).

meet the founder

After suffering a sports injury in 2007, I began to develop lower back pain and the MRI showed L4 and L5 herniated discs in my lower spine. I tried every remedy available, but every year I would throw my back out doing the most basic activities. Pain longer than 6 months is considered chronic pain and studies have shown people with chronic pain earn 35% less over their lifetime and are more likely to experience depression as well as negative consequences to their social lives. My back pain went on for over ten years. During that time, I tried everything from acupuncture, heavy pain medications, PT, sports massages, and finally chiropractors.

Eventually, the bills were not sustainable and the pain began to affect every area of my life. Always an entrepreneur, I was determined to find a solution so I resigned from my role as Martha Stewart’s Managing Director in NYC and buried myself in research as well as seeing dozens of eastern and western medicine doctors to absorb their learnings.

I never felt like my back would go out which would happen often when doing other methods. I felt safe and wanted to replicate that feeling without spending so much money every month on classes and lessons. Pilates was special but it wasn’t practical for me or most Americans from a financial and time management standpoint.Then I met someone who explained to me that improving mobility in the legs would release the lower back because stress travels up and down the body and it’s all connected. This made ZERO sense to me but I was desperate. so I started doing YouTube videos and one in particular helped me the most, “legs up the wall.” I could feel my back improve immediately.

After being treated and speaking to some of the most accomplished physicians, clinicians, and healers, I finally learned that the key to fixing my back and many other chronic pain issues would be to improve mobility, strengthen my core, and address the tightness and weakness in my glutes and hamstrings.

At first, I tried stretching with traditional elastic resistance bands, ropes and green straps. I found that they were very painful to grip and didn’t create the toe dorsiflexion that was necessary to elongate the plantar fascia where EVERYTHING begins. Our toes must be pulled back and down for the ENTIRE posterior chain to activate AT THE SAME TIME which is why you always see the sports therapists pushing down on the toes and feet of their patients which creates a more effective stretch.

My goal was to change how chronic pain was being treated.

This would require that I design a solution which could achieve
1) Toe Dorsiflexion
2) Relaxing natural grip for longer stretch sessions
3) A more practical, convenient, and financially responsible solution that would target the ROOT cause of the chronic pain.

I began testing Castleflexx and after just a few days everything changed for me. I felt a release in my back I hadn’t felt before. Shortly thereafter, I felt noticeable improvement in many other areas. For example, I stopped getting plantar fasciitis completely. GONE. 

After a few months of using CastleFlexx for 8 to 16 minutes a day, I began to feel better, move better and even look better. My wife Carly, who had also begun using CastleflFlexx, experienced significant improvement and no longer complains about her hip pain and sciatica. Life just got better for both of us.

Overall, my experience can be described as a ripple effect - less pain -> more movement and activity -> feeling healthier and eating better -> weight loss and about a dozen other benefits, not to mention being less grumpy to my loved ones.

When we are in pain we are just not fun to be around and that’s NORMAL. After spending years of testing to develop the device that would help heal the ROOT cause of my chronic pain, I applied for the patents and once they were issued by the United States Patent Office I immediately began testing with elite athletes to see how it would work for them. The results were staggering.

This invention changed my life as well as my wife’s and we are very excited to finally make it available to everyone. We are overwhelmed with the response and success stories. We can't wait to show you what's coming next… 

Dan Castle



Ropes/Straps/Bands are stressful to grip for any period of time.

Can't achieve toe dorsiflexion


Pressing the bottom foot against any object didn’t work for Dan Castle. Has it ever worked?! Creating elongation of the plantar fascia is more effective.


Heavy & Bulky

Limited to one target area