The Physical Stress Theory

Tissue Adaptation to Physical Stress: a proposed "Physical Stress Theory" to guide Physical Therapy Practice, Education and Research, an article by Mueller and Maluf, is a must read for any physical therapy student. At SLU, I was required to read it during my first semester in the program. At the time, I did not fully understand the full extent or importance of the article. Mueller and Maluf touch on several key concepts that directly relate to our patient care. 

The premise behind the Physical Stress Theory (PST) is "that changes in the relative level of physical stress cause a predictable adaptive response in all biological tissues." When stresses are placed on a particular structure due to movement or posture for example, our bodies tissues must adapt to these stresses. Stress can be defined by Magnitude x Time x Direction, and it is a combination of these 3 factors that will determine our bodies response. Our goal as physical therapists is to identify patterns that lead to excessive stresses and teach the patient proper movement strategies to prevent further tissue injuries. After identifying the problem, we need to decrease pain and perceived level of disability, and then focus on increasing activity tolerance in the new pain-free movement pattern. During any initial evaluation, think about a) What factors are causing excessive stress (environmental, behavioral, etc.) and b) How can these factors be modified?

A few crucial take-home points from the PST:
-Movement is a significant source of physical stress. Depending on how we move can have either detrimental or beneficial effects on tissue injury. 
-4 Fundamental tissues that undergo stress regularly are Epithelial, Connective, Muscular, and Nervous tissue. 
-5 Qualities of physical stress include: Decreased stress tolerance, Maintenance (homeostasis), Increased stress tolerance (tissue overload), Injury, and Death. The article goes into great detail on each of these points.
-Stress will have different effects on tissues whether it is tensile, compressive, shearing, or torsional stress. Regardless which type of stress is present, inflammation will occur immediately following tissue injury. 
-Postural deviations are one of the most common causes of musculoskeletal pain.
-Tissues atrophy at a much faster rate than they hypertrophy. Muscle force production losses can be between 6-40% in 4-6 weeks time. 
-Similar to muscles, nerves can become overused due to malalignment and postural deficits. This is commonly seen in carpal tunnel sydrome and lumbar spinal stenosis. 

Bottom Line: Good Alignment + Good Movement = Good Musculoskeletal Health. Factors such as posture, age, movement patterns, psychological factors and environmental factors all influence this equation. It is our goal to identifty these factors to allow for normal movemen

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Mueller and Maluf. Tissue Adaptation to Physical Stress: a proposed "Physical Stress Theory" to guide Physical Therapy Practice, Education and Research. Physical Therapy. 2002. 84.4: 383-403. Web. 2010.