FLEX by John Haddad
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FLEX:
True Functions of the Most Controversial Muscles by John Haddad
Redefine how you think about movement with FLEX, the book that challenges traditional views on biomechanics and muscle function. Written by movement expert John Haddad, this guide unravels the mysteries of the body’s true mechanics, offering science-backed insights that are reshaping the world of fitness and rehabilitation.
What Sets FLEX Apart?
FLEX isn’t just another fitness manual—it’s a fresh perspective on how the body truly works. Haddad combines cutting-edge science with a practical, easy-to-read style, making complex concepts accessible to everyone from elite athletes to everyday movers. Dive deep into the connection between muscles and the brain, explore the role of the fascia, and discover how momentum and sling systems can transform your movement efficiency.
Inside, You’ll Find:
- New Perspectives on Biomechanics: Challenge outdated theories and learn innovative techniques for better movement and recovery.
- Gentle Guidance with a Sense of Humor: Enjoy Haddad’s lighthearted yet insightful approach, making it easy to grasp even the most technical aspects.
- Understanding Pain as Communication: Reframe your relationship with pain, seeing it as a valuable signal rather than an obstacle.
Who Should Read FLEX?
Ideal for athletes, gym owners, trainers, and anyone eager to deepen their understanding of the body, FLEX provides practical tools for improving performance, preventing injuries, and achieving lasting physical health. Whether you're looking to optimize your workouts or simply move better in daily life, FLEX offers the insights you need.
Why It Matters:
FLEX has the power to change how we approach movement and rehabilitation. By embracing its concepts, you’ll not only enhance your own well-being but also contribute to a healthier, pain-free future for all.


Trainer Bio
John Haddad is a scientist and educator known in the biomechanics and movement world globally. He has been working as a “movement therapist” since 2011 and became known for fixing problems that couldn’t get fixed through the regular channels. This led him on a journey of figuring out how the body really works. Read More
His methods are based on fixing the body by teaching it to do the right movements right. His philosophy lies in his firm belief that “the brain controls the body and almost everything becomes easy once you understand how to program it.”
John carries out a wide range of training methods based on the right movements. He founded the Level-8 School of Biomechanics and Movement Therapy and helps elite athletes, primarily football players in the top leagues train better, recover better and move better.
The international media describes John as the “Miracle Man” due to his interventions with world-class athletes.
John dedicates his time to science, research and development, and training. He wrote his book Flex in 2021 and has been invited as a guest speaker on different panels, conferences and platforms around the world. His passion is reflected in his extensive training programs that he implements worldwide.