What did D.D. Palmer focus on that marked his materialist concerns?

D.D. Palmer, the founder of chiropractic, emphasized the concept that physical health issues could arise from misalignments in the spine that lead to nerve interference. His materialist concerns were grounded in the idea that tangible, physical structures, specifically the joints and their proper alignment, played a crucial role in maintaining health. By focusing on material joints impinging on nerves, he highlighted the importance of structural integrity in the body as a basis for overall wellness. This perspective set the foundation for chiropractic practices that seek to adjust and align the spine to restore health and function.

The other options, while related to health in various ways, do not represent Palmer's primary focus. Psycho-spiritual healing and emotional well-being engage more abstract or holistic practices, and energy flow in the body corresponds more with concepts found in other healing traditions, such as acupuncture or certain holistic health philosophies. In contrast, Palmer's approach was distinctly rooted in the physical and material aspects of the body, making the focus on joints and their relation to nerve function essential to understanding his contributions to chiropractic care.