Content area
Full Text
The purpose of this perspective is to present a general theory-the Physical Stress Theory (PST). The basic premise of the PST is that changes in the relative level of physical stress cause a predictable adaptive response in all biological tissue. Specific thresholds define the upper and lower stress levels for each characteristic tissue response. Qualitatively, the 5 tissue responses to physical stress are decreased stress tolerance (eg, atrophy), maintenance, increased stress tolerance (eg, hypertrophy), injury, and death. Fundamental principles of tissue adaptation to physical stress are described that, in the authors' opinion, can be used to help guide physical therapy practice, education, and research. The description of fundamental principles is followed by a review of selected literature describing adaptation to physical stress for each of the 4 main organ systems described in the Guide to Physical Therapist Practice (ie, cardiovascular/pulmonary, integumentary, musculoskeletal, neuromuscular). Limitations and implications of the PST for practice, research, and education are presented. [Mueller MJ, Maluf KS. Tissue adaptation to physical stress: a proposed "physical stress theory" to guide physical therapist practice, education, and research. Phys Then. 2002;82:383-403.]
Key Words: Adaptation, Biomechanics, Force, Stress.
Physical therapists have expertise in the application of interventions-such as exercise, postural instruction, orthotic devices, and modalities-that allow them to modify the physical stresses applied to tissues of the body.1-5 Physical stress is defined as the force applied to a given area of biological tissue.6 Exercise interventions that modify physical stress have been shown to decrease impairments, functional limitations, disability, and pain in a variety of patient populations.7-9 These same interventions can help people with and without disease increase muscle performance,10 bone mineral density,11 and fitness levels.9 An increasing amount of evidence indicates that exercise can have positive effects on disease processes such as diabetes,12 arthritis,7-9 and coronary artery disease.13
We believe that the many different theories and approaches currently used in physical therapy share fundamental principles that can be organized into a general theory to guide prevention and treatment of a broad range of patient problems. The general theory we present is based on fundamental principles that appear to govern the adaptive response of biological tissues to physical stress. Therefore, we refer to this theory as the Physical Stress Theory (PST). The PST integrates existing...