Clinical, Biomechanical, and Physiological Translational Interpretations of Human Resting Myofascial Tone or Tension

Background: Myofascial tissues generate integrated webs and networks of passive and active tensional forces that provide stabilizing support and that control movement in the body. Passive [central nervous system (CNS)–independent] resting myofascial tension is present in the body and provides a low-level stabilizing component to help maintain balanced postures. This property was recently called “human resting myofascial tone” (HRMT). The HRMT model evolved from electromyography (EMG) research in the 1950s that showed lumbar muscles usually to be EMG-silent in relaxed gravity-neutral upright postures. Methods: Biomechanical, clinical, and physiological studies were reviewed to interpret the passive stiffness properties of HRMT that help to stabilize various relaxed functions such as quiet balanced standing. Biomechanical analyses and experimental studies of the lumbar multifidus were reviewed to interpret its passive stiffness properties. The lumbar multifidus was illustrated as the major core stabilizing muscle of the spine, serving an important passive biomechanical role in the body. Results: Research into muscle physiology suggests that passive resting tension (CNS-independent) is generated in sarcomeres by the molecular elasticity of low-level cycling cross-bridges between the actomyosin filaments. In turn, tension is complexly transmitted to intimately enveloping fascial matrix fibrils and other molecular elements in connective tissue, which, collectively, constitute the myofascial unit. Postural myofascial tonus varies with age and sex. Also, individuals in the population are proposed to vary in a polymorphism of postural HRMT. A few people are expected to have outlier degrees of innate postural hypotonicity or hypertonicity. Such biomechanical variations likely predispose to greater risk of related musculoskeletal disorders, a situation that deserves greater attention in clinical practice and research. Axial myofascial hypertonicity was hypothesized to predispose to ankylosing spondylitis. This often-progressive deforming condition of vertebrae and sacroiliac joints is characterized by stiffness features and particular localization of bony lesions at entheseal sites. Such unique features imply concentrations and transmissions of excessive force, leading to tissue micro-injury and maladaptive repair reactions. Conclusions: The HRMT model is now expanded and translated for clinical relevance to therapists. Its passive role in helping to maintain balanced postures is supported by biomechanical principles of myofascial elasticity, tension, stress, stiffness, and tensegrity. Further research is needed to determine the molecular basis of HRMT in sarcomeres, the transmission of tension by the enveloping fascial elements, and the means by which the myofascia helps to maintain efficient passive postural balance in the body. Significant deficiencies or excesses of postural HRMT may predispose to symptomatic or pathologic musculoskeletal disorders whose mechanisms are currently unexplained

Sexual Dimorphisms of Adrenal Steroids, Sex Hormones, and Immunological Biomarkers and Possible Risk Factors for Developing Rheumatoid Arthritis

Innate immunity and immunological biomarkers are believed to be interrelated with sex hormones and other neuroendocrine factors. Sexual dimorphism mechanisms may be operating in certain rheumatic and inflammatory diseases which occur more frequently in women than men, as rheumatoid arthritis (RA). Less data have been available on altered interrelations of the combined neuroendocrine and immune (NEI) systems as risk factors for development of certain diseases. In this study, serological interrelations of NEI biomarkers are analyzed before symptomatic onset of RA (pre-RA) versus control (CN) subjects, stratified by sex. Sexual dimorphism was found in serum levels of acute serum amyloid A (ASAA), soluble interleukin-2 receptor alpha (sIL-2Rα), and soluble tumor necrosis factor receptor 1 (sTNF-R1). Multiple steroidal and hormonal (neuroendocrine) factors also showed highly (p<0.001) significant sexual dimorphism in their assayed values, but less for cortisol (p=0.012), and not for 17-hydroxyprogesterone (p=0.176). After stratification by sex and risk of developing RA, differential NEI correlational patterns were observed in the interplay of the NEI systems between the pre-RA and CN groups, which deserve further investigation

Human Resting Muscle Tone (HRMT): Narrative Introduction and Modern Concepts

Human resting muscle (myofascial) tone (HRMT) is the passive tonus or tension of skeletal muscle that derives from its intrinsic (EMG-silent) molecular viscoelastic properties. The word tone has been used to convey varying clinical and physiological features that have led to confusion and controversy. HRMT is the vital low-level, passive tension, and resistance to stretch that contributes importantly to maintaining postural stability in balanced equilibrium positions. In contrast, co-contraction of muscle is an active neuromotor control that provides greater levels of tonus for increased stabilization. Functionally, HRMT is integrated with other passive fascial and ligamentous tensional networks of the body to form a biotensegrity system. This review aims to achieve better understandings of HRMT and its functional roles. Nature is frugal and Man’s adaptations to gravitational forces and erect postures seemingly evolved mechanisms in skeletal muscle tissues to economically enhance stability. Normal passive muscle tone helps maintain relaxed standing body posture with minimally increased energy costs (circa 7% over supine), and often for prolonged durations without fatigue. Available data infer polymorphic variations in normal myofascial tone. However, few quantitative studies have been performed to establish normal frequency distributions of degrees of myofascial tone. Clinical experience indicates that persons with certain symptomatic musculoskeletal conditions may have palpably increased resting muscle firmness or hardness (EMG-silent), such as that of the upper trapezius in tension-type headache, and the lumbodorsal extensors (hartspann) in degenerative lumbar disc disease and ankylosing spondylitis. In summary, resting skeletal muscle tone is an intrinsic viscoelastic tension exhibited within the body’s kinematic chains. It functions inseparably from fascial (i.e. myofascial) tissues and ligamentous structures. Thus, HRMT is a passive myofascial property which operates within networks of tensional tissues, i.e., biotensegrity. This passive tension is the CNS-independent component resulting from intrinsic molecular interactions of the actomyosin filaments in sarcomeric units of skeletal muscle and myofibroblast cells. The overarching CNS-activated muscle contractions generate far greater tensions transmitted by fascial elements. Interdisciplinary research on HRMT and its biodynamics promises greater effectiveness of clinical practitioners and productivity of investigators, which warrants priority attention

Do women with premenopausal-onset rheumatoid arthritis have relative insufficiency or imbalance of adrenocortical steroids?

Adrenocortical steroids may influence susceptibility to rheumatoid arthritis (RA). Serum levels of adrenocortical steroids in female RA patients not previously treated with glucocorticoids were reviewed in this paper, as were controlled cohort studies of predisease (pre-RA) and control (CN) women. Serum dehydroepiandrosterone sulfate (DHEAS) levels were lower in most reports of premenopausal-onset RA patients not treated with glucocorticoids and in the baseline levels in one cohort study of pre-RA females compared with CN subjects. The pre-RA versus CN cohort difference was confirmed in an independent laboratory. Basal DHEAS and cortisol levels correlated oppositely in pre-RA versus CN women, suggesting relative adrenocortical androgenic insufficiency in case subjects. Clinical observations of lower androstenedione levels in premenopausal RA patients were also reported in pre-RA versus CN subjects who had lower DHEAS and cortisol values. In summary, a minority of premenopausal-onset RA females had decreased adrenocortical androgenic steroid levels and exhibited an adrenal androgen-to-cortisol steroid imbalance

Lower Serum Androstenedione Levels in Pre-Rheumatoid Arthritis versus Normal Control Women: Correlations with Lower Serum Cortisol Levels

Serum adrenal androgens (AAs), including androstenedione (Δ4A) and dehydroepiandrosterone sulfate (DHEAS), have been reported to be lower in female rheumatoid arthritis (RA) patients with early disease. Few data are available on hormonal status of women before the onset of clinical rheumatoid arthritis (pre-RA). A broad baseline panel of serum adrenal and sex steroids was compared in 36 female pre-RA to 144 matched cohort control (CN) subjects to determine differences in their mean values and in patterns of hormonal correlations. Study subjects having lower versus higher baseline serum cortisol levels than the total group's mean value were also analyzed separately to investigate differences in their hormonal levels and correlational patterns. In total subjects, mean (±SE) Δ4A level (nmol/L) was lower (P=0.018) in 28 pre-RA cases (6.4±0.40) versus 108 CN (7.8±0.28). The significant (P=0.013) difference was restricted to 9 pre-RA versus 53 CN subjects having lower cortisol levels (5.6±0.73 versus 8.0±0.42 nmol/L, resp.). In total subjects, no significant difference was found between study subjects in their bivariate correlations of the hormonal panel variables, unlike results found in the subgroups stratified by lower versus higher cortisol levels. A subgroup of pre-RA females may have relative adrenal cortical insufficiency, as reflected by lower Δ4A, especially observed among those subjects with lower cortisol levels