Proprioceptive Derivation (pd): The Core of Ergonomics

(The following are excerpts from a paper presented to the Japan Society of Human Factors in May, 1992)

“Pd –The Key To Linkage of Skills, Settings and Technology–An Example of pd Linkage In Health Care”
Daryl Beach DMD, LAN Center, Osaka, Japan


The industrial age produced a health care field that is heavily dependent on technology. It also produced a great demand for standards. This has resulted in accredited curriculums that produce licensed personnel from medical, dental, nursing, pharmaceutical and other schools. Also, with a concern for safety, national and international standards organizations have regulated or set standards for drugs, equipment, devices, health care settings and information.

On the other hand, standards for skills do not exist beyond the range of individual schools, hospitals or service organizations. While there is much interest in restoring the abilities or health of the human body, there has been little interest in determining optimum use of the human body for providing health care. Skill is simply identified as an ability to achieve desired outcomes with applications focused on various parts, functions, and disorders of the human body. This has led to a large variety of specialties which are recognized at the administrative levels of governments and schools. In these specialties the ability to achieve given outcomes with poorly designed instruments or in compromised settings is often seen as a useful test of skill. This credit was certainly indicated in the early industrial period, but today, overall, it has negative value for patients and all who support the health care field, since it delays progress in health care.

Specialty-based skills

Specialty-centered skills are identified with careers, settings or techniques. “What do you do?” “I am a surgeon.” “What kind of surgeon?” “Abdominal.” “Are you using laparoscopic technique?” “As much as possible.” With these questions we have captured the image of a person’s career, the setting of activity and an interest in a technique. How does a surgeon with skills based on use of scalpels, probing fingers and tying sutures transfer his/her skills to use of laparoscopes? How many patients are at risk of complications–not because of the laparoscopy technology, but because of the problems of acquiring or transferring skills that are based on manuals and emulation with trial and error?

This is only one example of change that is taking place throughout the field of health care due to rapid and costly testing and adoption of new technologies. Specialty-based skills are centered on what we can do with what we have now, what we are teaching now, or how our present “new” techniques compare with the past conditions of our specialty. From this point of view, we often see progressive changes mixed with retrogressive changes.

The following are problems of specialty centered skills;

  • 1 Inability to differentiate skill problems from problems of settings or technology,
  • 2 High cost and unnecessary risk to patients due to accommodation of specialty centered skills in the health care field,
  • 3 Difficulty in acquiring and transferring skills due to lack of principle for procedure,
  • 4 Inability to correlate use of one’s body with consistent accuracy in outcomes and productivity,
  • 5 Confusion and needless stress for patients, providers, engineers, students and administrators due to the above mentioned problems.

Pd skill – Optimum use of the human body

Pd skill is acquired from derivations in open space with no preconceptions and then pd muscle memory sets are established and maintained in pd settings. Pd-based skill can cover all specialties now and in the future, while specialty-based skills reflect past habits and the use of dated technology associated with specialty techniques.

What is the key to linkage of skills, settings and technology? Wilfred Barlow, MD pointed out in his book, “The Alexander Principle,” that misuse of the neck results in misuse of the rest of the body, including the fingers, lower back, feet, jaws and eyes. The optimum use of the body begins with the use of the neck, from which we can proprioceptively derive the optimal use of remaining muscles of the body. The use of the neck can be specified for both resting conditions and purpose-oriented activities. It is not only the key for determination of skills, settings and human interface with technology, but it also affects musculo-skeletal health which, in turn, may affect the health of other organs.

Use of the neck can be analyzed from tracings of one or more points on the head in relation to other points on the body. Also EMGs and X-rays have been widely used, particularly in studies of neck-associated pain. After the parameters of the head-trunk relationship have been established for achieving a desired outcome, then the 0 locations and paths of motions of the remaining segments of the body can be traced with a high focus on finger points and instrument points. Accuracy of outcomes is highly measureable.

When should we be concerned with the use or misuse of the human body? We are concerned with it when consistent accuracy is required, when our judgments on skills, settings and technology affect the lives of many, and when we want to prevent or correct personal health problems caused by misuse of our bodies.


The study of human factors deals with the interface between human beings and settings. Today, especially in health care settings, human beings interface extensively with specialized treatment and information technology, often in the form of big machines. Human interface engineers must know the appropriate basis for human acts before specifying the human-setting/technology interfaces.

In summary:

  • 1. Pd is the core of ergonomics.
  • 2. Pd skill is needed for the field of health care.
  • 3. Pd skill needs pd space, pd settings and pd technology.

Editors Note: Dr. Beach wrote the article above17 years ago. Today those practicing pd dentistry are more convinced that a principle of pd is needed in health care as we are experiencing a global financial adjustment that has illuminated waste and self-serving businesses. The public is witnessing the interface of an emerging survival-safety-health (SSH) economy with a group-personal choice economy that now seems to be leading to great waste of material resources and human energy recognized by world leaders. Commitment to human-centered standards in the dental industry and in dental clinics would be a demonstrable move toward the SSH economy. Patients want control of their bodies, safety for themselves, and to be reassured they are receiving the best care and the best care options for their health care dollars, insurance premiums, and taxes allocated for health care. Pd conditions can address these concerns in addition to being the core of ergonomics for safe musculoskeletal practice by the health care provider. The outcomes of applying pd result in skillful use of the body and ensure that human performance is measurable and verifiable. It reflects the essential principle of ergonomic functioning—using the least human effort and material resources needed for a procedure that does not contribute to body disorders, to errors in procedures, and to unacceptable outcomes due to fatigue, stress, and strain.

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