Responsiveness of Muscle Tone Characteristics to Progressive Force Production

Abstract

It is possible to measure muscle tone reliably, quickly and objectively using tonometers although they are not yet widely used. In clinical practice, it may be helpful if clinicians could assess the degree of contraction in different parts of a muscle without having to perform time-consuming electromyography measurements. The purpose of this study was to evaluate the responsiveness of different muscle tone characteristics to progressively increased contraction force of quadriceps muscle. Twenty healthy subjects (mean age 39.9 years, 50% women) volunteered. Using 2 different tonometers various muscle viscoelastic properties were measured. The frequency (hertz), logarithmic decrement, and stiffness (newtons per meter) of damped mechanical oscillation of the muscle tissue and tissue compliance (millijoules) were registered from rectus femoris muscle at rest and 20, 40, 60, 80% of maximal voluntary contraction determined using dynamometry. All the values changed linearly with increasing force level. Compliance, oscillation stiffness, and frequency parameters showed large effect sizes (ESs ≥ 0.8). The standardized respoknse mean for compliance was 5.3 (4.8-5.7) mJ, for oscillation stiffness 1.8 (1.3-2.2) N·m(-1), frequency 1.1 (0.6-1.5) Hz, and decrement -0.6 (-1.0 to -0.2). The results indicate that the compliance and oscillation stiffness parameters showed the highest responsiveness and can thus best detect changes in muscle contraction state. The additional value of using tonometers to measure these properties in clinical practice should be investigated further.

Practical Considerations for Standardized Recording of Muscle Mechanical Properties Using a Myometric Device: Recording Site, Muscle Length, State of Contraction and Prior Activity

“…This is in keeping with findings reported in a recent study where a linear increase in all three mechanical properties of RF with increasing force levels in 20 healthy participants with a mean age of 39.9 years was recorded. 23 Unlike the present study where only one level of MVC was assessed, the above study measured the change in RF properties with increasing force levels (20%, 40%, 60% and 80% MVC). They reported similar tone to that in the present study (relaxed ¼ 16:82 AE 1:9; contracted 19:01 AE 2:5 Hz at 30% MVC) at 40% MVC ðrelaxed ¼ 15:3 AE 2:0; contracted ¼ 19:0 AE 4:2 Hz), despite the difference in percentage MVC level for their participants.…”

Muscle tone assessments for children aged 0 to 12 years: a systematic review

“…Interestingly, we did not identify any assessments that were solely designed to measure muscle tone. This may explain why there is no criterion standard assessment of muscle tone recommended to date, since use of each identified muscle tone item will occur only after a broader developmental assessment has been selected. This finding is in contrast to other movement disorders such as spasticity or dyskinesia, for which there are a large number of symptom‐specific tools available.…”

“…Given such a large proportion of the population experiences difficulties with muscle tone, accurate assessment of muscle tone is essential for diagnostic, prognostic, and treatment planning purposes . However, no criterion standard muscle tone assessment has been endorsed to date …”

Associations between muscle myotonometry (a)symmetry and functional movement performance in young women and men

“…The muscle tone is most probably best described by the frequency of damped oscillations (Hz), when oscillations fade following a sudden mechanical effect. The greater the muscle tone, the more tense the muscle resulting in the greater frequency of damped oscillations [38,39].…”