Human resting muscle tone (HRMT): Narrative introduction and modern concepts

University of Illinois College of Medicine at Peoria, Peoria, IL 61656, USA.
Journal of bodywork and movement therapies 11/2008; 12(4):320-32. DOI: 10.1016/j.jbmt.2008.05.007
Source: PubMed


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 maintain 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 to 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.

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    • "The muscles of the neck and shoulder are the most affected in workers of different occupations, especially those that involve repetitive movements as typing in a computer for a long time [4] [5]. This pattern of muscle tension is found mainly in the upper fibers of the trapezius muscle, and for this reason, it is an area much investigated in the literature by electromyography [1] [4] [6]. Thus, the vicious cycle involving stress, repetitive activities, and tension in the trapezius also leads to greater difficulty in returning to basal muscle activity after a workday [5]. "
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    Journal of Back and Musculoskeletal Rehabilitation 05/2014; 28(1). DOI:10.3233/BMR-140482 · 0.71 Impact Factor
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    • "As one example, the passive stretch of a muscle meets with initial resistance that relaxes until the muscle shows a linear response to the force applied; this time-dependent resistance can be modelled by an arrangement of one or more springs that retain part of the force, and one or more dashpots that dissipate part of the force (Kubo et al 2001). Viscoelastic modelling has been shown to fit observed behaviour of muscle in static stretching (Gajdosik 2001, Walsh 1992), resting muscle tone (Simons and Mense 1998, Masi and Hannon 2008), explosive force (Jacobs et al 1996), fatigue (Lakie and Robson 1988), flexibility (Magnusson et al 1997), hypermobility (Magnusson et al 2001), and upright posture (Walsh 1992, Proske et al 1993). "
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    ABSTRACT: Skeletal muscle viscoelastic properties reflect muscle microstructure and neuromuscular activation. Elastographic methods, including magnetic resonance elastography, have been used to characterize muscle viscoelastic properties in terms of region of interest (ROI) measurements. The present study extended this approach to create thresholded pixel-by-pixel maps of viscoelastic properties of skeletal muscle during rest and knee extension in eleven subjects. ROI measurements were taken for individual quadricep muscles and the quadriceps region as a whole, and the viscoelastic parameter map pixels were statistically tested at positive false discovery rate q ⩽ 0.25. ROI measurements showed significant (p ⩽ 0.05) increase in storage modulus (G') and loss modulus (G″), with G″ increasing more than G', in agreement with previous findings. The q-value maps further identified the vastus intermedius as the primary driver of this change, with greater G″/G' increase than surrounding regions. Additionally, a cluster of significant decrease in G″/G' was found in the region of vastus lateralis below the fulcrum point of the lift. Viscoelastic parameter mapping of contracted muscle allows new insight into the relationship between physiology, neuromuscular activation, and human performance.
    Physiological Measurement 11/2013; 34(12):1675-1698. DOI:10.1088/0967-3334/34/12/1675 · 1.81 Impact Factor
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    • "The passive, resting (static) tone is independent of CNS control. It results from the elastic mechanical properties of the stable cross-bridges between the actin and myosin filaments of muscle fibers and the integrated connective tissue filaments [15, 20, 21]. "
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    12/2011; 2011(4):205904. DOI:10.1155/2011/205904
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