Hypertonia

Scientific basis

Muscle tone is the baseline state of tension of a muscle at rest. It combines an active component, related to the activity of muscle fibers, and a passive component, related to the viscoelastic properties of the muscle and connective tissues (Masi and Hannon 2008).

Neurological hypertonia. In neurology, the term has a precise meaning: spastic hypertonia, which increases with the speed of stretch, rigidity or dystonia, in the setting of a central nervous system disorder (Sanger et al. 2003). It is clearly distinct from ordinary muscle tension.

Functional muscle hypertonia. Outside this setting, the word covers distinct phenomena: increased muscle activity at rest or during a task, co-contraction, difficulty relaxing, protective contraction. Resistance to movement can also come from passive tissue stiffness, pain or apprehension, without excessive muscle activity.

Perineal hypertonia: the hypertonic pelvic floor. For the pelvic floor, the International Continence Society terminology distinguishes the contractile and viscoelastic components of tone, and describes an "overactive" pelvic floor: its muscles do not relax, or relax poorly, when relaxation is needed (Messelink et al. 2005; Frawley et al. 2021). A hypertonic pelvic floor may be associated with urinary, bowel or sexual difficulties, or with pelvic pain, without this association being enough to establish a single cause.

So-called myofascial hypertonia. The expression is used to link muscle tension, stiffness, pain and the neighboring connective tissues. It is a descriptive framework, not a diagnosis. Palpation cannot always distinguish muscle activity, tissue stiffness and provoked pain; the criteria for trigger points and myofascial pain syndrome vary across studies, and their diagnostic value remains debated (Quintner et al. 2015).

Blue Portance / SBNFA™ reading

In the SBNFA™ reading, hypertonia may reflect difficulty relaxing or a stabilization strategy in a given context. On its own, it does not allow one to conclude that there is a lesion, a fascial cause or a need to correct a posture. An observed tension is a clue, not a sufficient explanation.

Contribution to the analysis of sitting

Seating analysis does not measure muscle tone. It describes the conditions in which a person sits: pelvic orientation, distribution of support, room for micro-adjustments. A seat that leaves little room for variation may be accompanied by prolonged muscle holding; this observation remains a working hypothesis for interpretation and does not replace a clinical assessment.

Not to be confused with

Muscle overactivity, excessive activity of the muscles, which is only one of the possible components; Passive stiffness, resistance due to tissue properties, without contraction; Contracture, involuntary, sustained and localized contraction; Spasticity, the neurological form of hypertonia; Myofascial pain syndrome, localized muscle pain associated with tender areas; Trigger point, a tender area of a muscle, presented in this entry without an entry of its own; Fascial stiffness, a mechanical property of fascia; Pain, which can exist without measurable hypertonia, and vice versa; Functional asymmetry, a left-right difference in organization.

Related terms

Postural compensation · Myofascial continuity · Perineum · Pelvic floor · Fascial stiffness · Central sensitization · Myofascial pain syndrome · Fascial viscoelasticity · Functional asymmetry

Sources and scope

• Sanger et al. (2003): classification and definition of disorders causing hypertonia in childhood (Pediatrics)
• Masi and Hannon (2008): human resting muscle tone, current concepts (Journal of Bodywork and Movement Therapies)
• Messelink et al. (2005): standardization of terminology of pelvic floor muscle function and dysfunction, ICS report (Neurourology and Urodynamics)
• Frawley et al. (2021): ICS report on the terminology for pelvic floor muscle assessment (Neurourology and Urodynamics)
• Quintner, Bove and Cohen (2015): a critical evaluation of the trigger point phenomenon (Rheumatology)