ArticlePDF Available

Reliability, Validity, and Precision of a Handheld Myometer for Assessing in Vivo Muscle Stiffness

Journal of Sport Rehabilitation, 2011, e-pub only
© 2011 Human Kinetics, Inc.
Technical noTe
The authors are with the Dept of Exercise and Sport Science, University of North Carolina at Chapel
Hill, Chapel Hill, NC.
Reliability, Validity, and Precision
of a Handheld Myometer for Assessing
in Vivo Muscle Stiffness
Steven M. Zinder and Darin A. Padua
Biomechanically, muscle stiffness is the ratio of force response that results from
and resists mechanical stretch.1 The stiffness of the passive structures surrounding
a joint contributes little to its biomechanical stability except at the end ranges of
motion.2 Research has found, however, that the active stiffness properties of muscles
are essential to dynamic stability.3,4 Optimal levels of musculotendinous stiffness
are highly correlated to signicant increases in muscle performance.5 This increased
muscle stiffness surrounding a joint could limit the translation suffered by the joint
after an injurious perturbation.6 This in turn would limit strain on the ligamentous
structures, ultimately decreasing the incidence and severity of injury. Excessive
amounts of stiffness, such as the spasticity associated with cerebral palsy, can be
detrimental, however. Therefore, the ability to accurately quantify active muscle
stiffness in an attempt to identify the optimal level of stiffness is integral for both
clinicians and researchers.
To date, methods for measuring active muscle stiffness have used complicated
computer algorithms and sophisticated laboratory hardware, making accurate
assessment of muscle stiffness nearly impossible for clinicians. The oscillatory
method requires a sophisticated device to measure the frequency and decay of
transient motion oscillations at the joint along with a complicated mathematical
analysis to calculate the stiffness values. The passive force–position relationship,
wherein joint-force responses are measured at different passive joint angles, requires
a device that can accurately measure both joint position and force. In addition,
in both examples, the outcome measurement is essentially overall joint stiffness,
receiving contributions from the joint musculature, joint compression, and the
passive structures surrounding the joint. There is a need for clinicians to be able
to accurately measure the stiffness of individual muscles to isolate specic issues
to be addressed in rehabilitation.
A handheld myometer is a device purported to accurately measure muscle
stiffness in individual muscles. Previous research5,7–9 has shown that other methods
of muscle-stiffness measurement (e.g., damped oscillatory and passive length–
tension) are sensitive to levels of muscle force output. Sex differences have also been
observed using these other measures of stiffness.7,10,11 Thus, we hypothesized that if
a handheld myometer provides a valid assessment of stiffness that we would observe
2 Zinder and Padua
similar patterns. Therefore, the purpose of this investigation was to examine the reli-
ability and validity of a handheld myometer for assessing skeletal-muscle stiffness.
20 subjects (6 men, 14 women; age 21.90 ± 2.93 y, height 170.46 ± 9.24 cm,
mass 72.01 ± 11.47 kg) with no known neuromuscular disorders volunteered to
participate in this study.
All data were collected using the Myoton-3 (Müomeetria Ltd, Estonia, EU)
handheld myometer (Figure 1). The tip of the myometer was placed on the tissue
perpendicular to the underlying muscle. Slight pressure on the tip activated an
electromagnet in the device, which exerted a local impact on the tissue by means
of a brief mechanical impulse. This caused a minor deformation of the underly-
ing muscle tissue. After the impact, the tip was quickly released, and the damped
oscillatory behavior (Figure 2) of the tissue was recorded by an accelerometer in
the device. The viscoelastic stiffness of the underlying tissue was calculated using
the following equation12:
C = 4π2m2Y2 + (θ/4m)
where Y = the oscillation frequency, Y = 1/T Hz, and θ is the logarithmic decrement
of oscillation damping (Figure 2): θ = ln(a1/a3).
All testing was performed in the sports medicine research laboratory at the
University of North Carolina at Chapel Hill. Each subject read and signed an
informed-consent form approved by the institutional review board and was given
the opportunity to ask questions if
any arose.
After we recorded demographic
data, subjects were positioned on a
Biodex System 3 isokinetic dyna-
mometer (Biodex Medical Systems,
Shirley, NY) per the manufactur-
er’s guidelines for knee extension
(Figure 1). The dynamometer arm
was locked with the subject’s knee
in 60° of exion for isometric test-
ing. Maximum voluntary isometric
contraction (MVIC) values were
calculated by averaging the peak
force output of three 5-second
maximal knee-extension contrac-
tions with 1 minute between exer-
tions. Five consecutive myometric
stiffness measurements were then Figure 1 — Myoton-3 and subject positioning.
Handheld Myometer to Assess in Vivo Muscle Stiffness    3
collected in a randomized order from the midbelly of the rectus femoris muscle
at each of 5 different activation levels: 10%, 20%, 30%, 40%, and 50% of the
subject’s MVIC. The subjects were given a 1-minute rest between testing con-
ditions. A visual display of percentage MVIC was provided to the subjects as
a reference for the graded contractions. They were permitted to practice until
they felt comfortable sustaining the specic level of contraction before testing
in each condition.
Statistical Analysis
Descriptive statistics were calculated for demographic information on age, height,
and body mass. A mixed-model repeated-measures ANOVA was computed to assess
rectus femoris viscoelastic-stiffness differences over the different load conditions
and across sexes. Separate intraclass correlation coefcients (ICC2,1) and standard
errors of measurement (SEMs) were performed across the 5 trials in each load
condition to assess trial-to-trial reliability and precision. All measurements were
collected by the same investigator (SMZ) and were analyzed with the Statistical
Package for the Social Sciences version 17.0 (SPSS, Chicago, IL).
Mean stiffness values for each of the load conditions were consistent with pre-
vious literature (Table 1).13 Post hoc analysis revealed that stiffness values at
10% load were signicantly different than those at 20%, 30%, 40%, and 50%
Figure 2 — Damped oscillatory behavior of the rectus femoris muscle (adapted from Vain
and Kums12). T, time from peak 1 to peak 3; a1, amplitude peak 1; a2, amplitude peak 2.
Table 1 Muscle Stiffness for the Individual Trials, N/m
% MVIC Gender 1 2 3 4 5 Mean SD
10% men 410.50 374.50 389.50 386.33 395.00 391.17 74.96
women 276.07 278.79 280.64 282.57 290.29 281.67 30.76
total 316.40 307.50 313.30 313.70 321.70 314.52 69.11 .28 .92 23.34
20% men 445.17 442.83 443.00 422.83 428.83 436.53 84.64
women 296.21 306.29 307.07 304.07 313.36 305.40 49.88
total 340.90 347.25 347.85 339.70 348.00 344.74 85.96 .41 .96 19.38
30% men 461.00 461.83 463.50 441.50 457.33 457.03 89.34
women 313.50 323.14 314.29 334.14 323.14 321.64 73.58
total 357.75 364.75 359.05 366.35 363.40 362.26 99.28 .81 .94 26.69
40% men 520.20 451.60 436.00 453.40 459.00 464.04 102.05
women 332.21 329.93 334.14 325.07 333.71 331.16 66.59
total 387.80 367.55 367.45 363.70 366.68 370.64 99.11 .35 .86 46.78
50% men 514.83 485.17 545.17 508.00 506.83 512.00 127.86
women 330.36 334.07 328.93 340.71 331.57 333.13 67.56
total 385.70 379.40 393.80 390.90 384.15 386.79 120.40 .78 .91 38.00
MVIC, maximal voluntary isometric contraction.
Handheld Myometer to Assess in Vivo Muscle Stiffness    5
Figure 3 Rectus femoris stiffness values across contraction levels. *10% < 20%, 30%,
40%, and 50%; 20% < 40% and 50%. MVIC, maximal voluntary isometric contraction.
loads and that 20% was signicantly different than stiffness levels at 40% and
50% MVIC (Figure 3). Men generated signicantly higher stiffness values than
women at each level of contraction (Figure 4). There was also a signicant load
× sex interaction that showed that the stiffness exhibited by men increased at a
greater rate at the higher level of contraction than did that of women, especially
at the 50% load level (Figure 4). Trial reliability and precision were excellent for
each load condition, with ICCs ranging from .86 to .96 and SEMs ranging from
19.38 to 46.78 N/m (Table 1).
Active muscle stiffness has been shown to be an integral component in decreasing
injurious joint translations.3,4 It is therefore important to be able to easily and accu-
rately quantify skeletal-muscle stiffness. Previously this has been difcult because
of the specialized equipment and techniques needed, but the current investigation
evaluated the reliability, validity, and precision of a handheld myometer, a user-
friendly instrument, to quantify muscle stiffness.
Reliability Analysis
The current data show that the handheld myometer produced reliable and precise
measurements of active muscle stiffness. It has been suggested that ICCs above .75
demonstrate good reliability, and those below .75 indicate moderate to poor reli-
6 Zinder and Padua
ability.14 The very high ICCs in the current study (.86–.96 across the different load
conditions) demonstrate that when the manufacturer’s recommended procedures
are strictly followed, clinicians and researchers can obtain very consistent active
muscle-stiffness measures across multiple trials. These values are comparable
to reliability of other methods of stiffness calculation presented in the literature
demonstrating ICCs ranging from .88 to .96.15,16
The extremely low SEMs, ranging from 5.6% to 12.6% of the mean stiffness
values, demonstrate excellent precision of the measurement when compared across
trials. This is comparable to other methods presented in the literature that demon-
strated SEMs ranging from 5.7% to 8.0% of the mean stiffness values.16 Although
measures at all levels of submaximal voluntary contraction examined showed high
reliability and excellent precision, the stiffness measures at 20% and 30% of MVIC
produced the highest reliability and greatest precision, suggesting they may be the
best choices for submaximal stiffness measurements.
Validity Analysis
Construct validity of the handheld myometer active muscle-stiffness measures was
established by comparing the change in stiffness values relative to the change in
Figure 4 — Rectus femoris stiffness values across contraction levels and sex. *Men sig-
nicantly greater at each contraction level.
Handheld Myometer to Assess in Vivo Muscle Stiffness    7
level of muscle contraction across sexes. Many studies on both in vitro9,17 and in
vivo5,7,8 muscle tissue have demonstrated that active muscle stiffness is proportional
to the level of muscle activation. In the current study active muscle-stiffness mea-
sures were collected at 10%, 20%, 30%, 40%, and 50% of the subjects’ MVIC,
causing a systematic increase in motor-unit recruitment as the level of contraction
increased. Although not all the stiffness values were statistically different across
contraction levels, the data trended toward a linear increase (R2 of .95) in active
stiffness levels with the increase in contraction level (Figure 3). This is consistent
with previous research using the Myoton.13
It has also previously been demonstrated that males consistently have greater
musculotendinous-stiffness values than females7,10,18 and that those differences
widen as torque production in the underlying muscle increases.18 These results
are mirrored in the current study, in which men had signicantly greater stiffness
values at each level of background contraction, with the greatest difference at the
50% MVIC load. The combination of the ability to detect increased stiffness values
with a concomitant increase in background muscle activity and accurately portray-
ing the stiffness characteristics across sexes suggest that the Myoton 3 is a valid
instrument to measure viscoelastic-stiffness properties of the musculotendinous unit.
Another advantage of the Myoton over existing stiffness-measurement tech-
niques is its ability to measure isolated muscles. With the standard oscillatory
technique of assessing muscle stiffness it is nearly impossible to isolate specic
muscles and avoid cocontraction of antagonist musculature. Cocontraction has
been shown to be a signicant contributor to joint stiffness,11,19 so the Myoton may
allow for a more specic measure of isolated muscle stiffness than currently used
techniques for stiffness assessment. This could be an invaluable tool for clinicians
to isolate specic muscles to evaluate their individual contributions to joint stability.
There are a few limitations and weaknesses to the current study. Most notably, only
1 aspect of validity, construct validity, was examined. There is no gold standard of
stiffness measurement in the literature, making comparisons to an accepted standard
difcult. Any of the previously used measures of stiffness use effective stiffness
measures that include contributions from all the surrounding musculature, passive
joint structures, joint compression, and so on. No other measurement technique we
are aware of allows for in vivo stiffness measures of individual muscles. There were
also unequal numbers of subjects in the gender groups. There was still adequate
statistical power to elucidate group differences, but future investigations should
place greater emphasis on similarity in sample size. Also, future studies should
examine other aspects of reliability, such as intratester and day-to-day reliability
of the measure, to get a more complete picture of the myometer’s reliability.
The results of this study suggest that a handheld myometer may be an effective
clinical measure of active muscle stiffness. The valid, reliable, and precise mea-
surements it collects combined with its ease of use and ability to measure active
muscle stiffness in specic, individual muscles make it a valuable tool to any
8 Zinder and Padua
practitioner or researcher interested in in vivo biomechanical properties of skeletal
muscle. Although myometry may not completely replace the computer algorithms
and sophisticated hardware needed in many applications, this simple device shows
promise as a tool in many research laboratories and therapy clinics.
1. Rack P, Westbury D. The effects of length and stimulus rate on tension in the isometric
cat soleus muscle. J Physiol (Lond). 1969;204(2):443–460.
2. Crisco JJ, Panjabi MM. Euler stability of the human ligamentous lumbar spine: part I
theory. Clin Biomech. 1992;7:19–26.
3. Duan XH, Allen RH, Sun JQ. A stiffness-varying model of human gait. Med Eng Phys.
4. Wagner H, Blickhan R. Stabilizing function of skeletal muscles: an analytical investiga-
tion. J Theor Biol. 1999;199:163–179.
5. Wilson GJ, Wood GA, Elliott BC. Optimal stiffness of series elastic component in a
stretch-shorten cycle activity. J Appl Physiol. 1991;70(2):825–833.
6. Wojtys EM, Ashton-Miller JA, Huston LJ. A gender-related difference in the contribu-
tion of the knee musculature to sagittal-plane shear stiffness in subjects with similar
knee laxity. J Bone Joint Surg Am. 2002;84(1):10–16.
7. Granata KP, Padua DA, Wilson SE. Gender differences in active musculoskeletal
stiffness: part II: quantication of leg stiffness during functional hopping tasks. J
Electromyogr Kinesiol. 2002;12(2):127–135.
8. McNair PJ, Hewson DJ, Dombroski E, Stanley SN. Stiffness and passive peak force
changes at the ankle joint: the effect of different joint angular velocities. Clin Biomech
(Bristol, Avon). 2002;17(7):536–540.
9. Rack PMH, Westbury DR. The short range stiffness of active mammalian muscle and
its effect on mechanical properties. J Physiol. 1974;240:331–350.
10. Blackburn JT, Padua DA, Weinhold PS, Guskiewicz KM. Comparison of triceps surae
structural stiffness and material modulus across sex. Clin Biomech (Bristol, Avon).
11. Granata KP, Padua DA, Wilson SE. Functional leg stiffness differences between genders.
J Electromyogr Kinesiol. 2002;12:127–135.
12. Vain A, Kums T. Criteria for preventing overtraining of the musculoskeletal system of
gymnasts. Biol Sport. 2002;19(4):329–346.
13. Bizzini M, Mannion AF. Reliability of a new, hand-held device for assessing skeletal
muscle stiffness. Clin Biomech (Bristol, Avon). 2003;18(5):459–461.
14. Portney LG, Watkins MP. Foundations of Clinical Research Applications to Practice.
2nd ed. Upper Saddle River, NJ: Pretice Hall Health; 2000.
15. Stanton TR, Kawchuk GN. Reliability of assisted indentation in measuring lumbar
spinal stiffness. Man Ther. 2009;14(2):197–205.
16. Zinder SM, Granata KP, Padua DA, Gansneder BM. Validity and reliability of a new
in vivo ankle stiffness measurement device. J Biomech. 2007;40(2):463–467.
17. Julian FJ, Sollins MR. Variation of muscle stiffness with force at increasing speeds of
shortening. J Gen Physiol. 1975;66:287–302.
18. Granata KP, Wilson SE, Padua DA. Gender differences in active musculoskeletal
stiffness: part I: quantication in controlled measurements of knee joint dynamics. J
Electromyogr Kinesiol. 2002;12(2):119–126.
19. Padua DA, Arnold BL, Perrin DH, Gansneder BM, Carcia CR, Granata KP. Fatigue,
vertical leg stiffness, and stiffness control strategies in males and females. J Athl Train.
... 51 Numerous studies have been performed with different myotonometric devices to determine the reliability of tissue stiffness and compliance measures. 23,28,30,39,47,52,53 In healthy populations in which a mix of upper and lower extremity muscles has been studied across various contraction intensities (0%-100%), good to excellent levels of testretest reliability were consistently demonstrated (ICCs . 0.75). ...
... 0.75). 23,52,53 Additionally, researchers who examined the use of myotonometry in individuals with neuromusculoskeletal conditions found moderate to excellent reliability (ICCs . 0.60). ...
... Stiffness as a Surrogate for Activation and Force Production. Several researchers 13,20,22,23 have used different myotonometric devices to determine how musculotendinous stiffness is correlated with neuromuscular activation (surface electromyography) and force production (dynamometry). Some myotonometric devices quantify stiffness through the inverse measure of compliance (Table 1). ...
Full-text available
Myotonometry is a relatively novel method used to quantify the biomechanical and viscoelastic properties (stiffness, compliance, tone, elasticity, creep, and mechanical relaxation) of palpable musculotendinous structures with portable mechanical devices called myotonometers. Myotonometers obtain these measures by recording the magnitude of radial tissue deformation that occurs in response to the amount of force that is perpendicularly applied to the tissue through a device's probe. Myotonometric parameters such as stiffness and compliance have repeatedly demonstrated strong correlations with force production and muscle activation. Paradoxically, individual muscle stiffness measures have been associated with both superior athletic performance and a higher incidence of injury. This indicates optimal stiffness levels may promote athletic performance, whereas too much or too little may lead to an increased risk of injury. Authors of numerous studies suggested that myotonometry may assist practitioners in the development of performance and rehabilitation programs that improve athletic performance, mitigate injury risk, guide therapeutic interventions, and optimize return-to-activity decision-making. Thus, the purpose of our narrative review was to summarize the potential utility of myotonometry as a clinical tool that assists musculoskeletal clinicians with the diagnosis, rehabilitation, and prevention of athletic injuries.
... Although myotonometry has exhibited moderate to excellent test-retest reliability (ICC = 0.60-0.98) with stiffness measures of several trunk and lower extremity muscles, [19][20][21] no studies have investigated reliability or precision (standard error of measurements [SEM] and minimal detectable changes [MDC]) of stiffness measures in lumbar spine and thigh musculature with individuals in standing or squatting postures. The lack of studies investigating muscle stiffness in these postures has precluded the establishment of normative healthy ranges that could possibly be used as a standard for comparison against those with musculoskeletal conditions and prevents researchers and clinicians from determining if myotonometry is a precise monitoring method capable of quantifying muscle stiffness changes following interventions. ...
... These findings are consistent with previous studies where reliability was found to be good to excellent (ICC = 0.88-0.99) in erector spinae, VL, and BF muscles that were measured with participants in supported positions (prone, supine, and seated) and/or while performing prescribed intensities of muscle contractions. [19][20][21][30][31][32] Furthermore, these findings support our hypothesis that myotonometry measurements collected in individuals in functional body positions would demonstrate acceptable reliability and may justify the expanded use of myotonometry in both research and clinical settings. ...
... Although participants were instructed to stand with their arms crossed in front of their body, it was not specified how high they should cross their arms; therefore, the height of arm crossing may have varied between the two measures. Because the height of anterior load carriage (in this case, the height of arms crossed in front of the body) can have a significant effect on LT muscle activation 33 and muscle activation and stiffness have a linear relationship, 19,21,34,35 the potential changes in arm height may have led to differences in testretest stiffness values and negatively affected reliability magnitude. Future studies should consider using a standing posture without an anterior load component (e.g., arms at sides) to potentially improve reliability of standing LT stiffness measurements. ...
Full-text available
Introduction Low back and lower extremity injuries are responsible for the highest percentage of musculoskeletal injuries in U.S. Army soldiers. Execution of common soldier tasks as well as army combat fitness test events such as the three-repetition maximum deadlift depends on healthy functioning trunk and lower extremity musculature to minimize the risk of injury. To assist with appropriate return to duty decisions following an injury, reliable and valid tests and measures must be applied by military health care providers. Myotonometry is a noninvasive method to assess muscle stiffness, which has demonstrated significant associations with physical performance and musculoskeletal injury. The aim of this study is to determine the test–retest reliability of myotonometry in lumbar spine and thigh musculature across postures (standing and squatting) that are relevant to common soldier tasks and the maximum deadlift. Materials and Methods Repeat muscle stiffness measures were collected in 30 Baylor University Army Cadets with 1 week between each measurement. Measures were collected in the vastus lateralis (VL), biceps femoris (BF), lumbar multifidus (LM), and longissimus thoracis (LT) muscles with participants in standing and squatting positions. Intraclass correlation coefficients (ICCs3,2) were estimated, and their 95% CIs were calculated based on a mean rating, mixed-effects model. Results The test–retest reliability (ICC3,2) of the stiffness measures was good to excellent in all muscles across the standing position (ICCs: VL = 0.94 [0.87–0.97], BF = 0.97 [0.93–0.98], LM = 0.96 [0.91–0.98], LT = 0.81 [0.59–0.91]) and was excellent in all muscles across the squatting position (ICCs: VL = 0.95 [0.89–0.98], BF = 0.94 [0.87–0.97], LM = 0.96 [0.92–0.98], LT = 0.93 [0.86–0.97]). Conclusion Myotonometry can reliably acquire stiffness measures in trunk and lower extremity muscles of healthy individuals in standing and squatting postures. These results may expand the research and clinical applications of myotonometry to identify muscular deficits and track intervention effectiveness. Myotonometry should be used in future studies to investigate muscle stiffness in these body positions in populations with musculoskeletal injuries and in research investigating the performance and rehabilitative intervention effectiveness.
... There is no gold standard of stiffness measurement in the literature, m comparisons to an accepted standard difficult [51,52]. In the absence of a criter measuring stiffness [51,52], the validity of the myotonometry tool has ofte determined by construct validity [51]. ...
... There is no gold standard of stiffness measurement in the literature, m comparisons to an accepted standard difficult [51,52]. In the absence of a criter measuring stiffness [51,52], the validity of the myotonometry tool has ofte determined by construct validity [51]. From these perspectives, myotonometry co ...
... There is no gold standard of stiffness measurement in the literature, making comparisons to an accepted standard difficult [51,52]. In the absence of a criterion for measuring stiffness [51,52], the validity of the myotonometry tool has often been determined by construct validity [51]. ...
Full-text available
Several tools have been used to assess muscular stiffness. Myotonometry stands out as an accessible, handheld, and easy to use tool. The purpose of this review was to summarize the psychometric properties and methodological considerations of myotonometry and its applicability in assessing scapular muscles. Myotonometry seems to be a reliable method to assess several muscles stiffness, as trapezius. This method has been demonstrated fair to moderate correlation with passive stiffness measured by shear wave elastography for several muscles, as well as with level of muscle contraction, pinch and muscle strength, Action Research Arm Test score and muscle or subcutaneous thickness. Myotonometry can detect scapular muscles stiffness differences between pre- and post-intervention in painful conditions and, sometimes, between symptomatic and asymptomatic subjects.
... The application of short pulses of the MyotonPRO ® to the underlying tissue will trigger a muscle deformation, and the resulting oscillation will be measured and analysed by the device [13]. We hypothesised that this device might allow a statement concerning the severity of myotonia or stiffness and could be used in evaluating disease progression. ...
... After the measurement is completed, the coefficient of variation will be displayed as a percentage next to every parameter [12]. The functionality of the MyotonPRO ® , measurement and calculations have been tested and validated in many clinical studies [9,10,13]. Therefore, this study is not intended to validate the measurements of the MyotonPRO ® device itself nor its safety or accuracy of measures. The primary outcome is to evaluate measurement results in patients with neuromuscular diseases and elaborate reference values. ...
Full-text available
Neuromuscular disorders show extremely varied expressions of different symptoms and the involvement of muscles. Non-invasively, myotonia and muscle stiffness are challenging to measure objectively. Our study aims to test myotonia, elasticity, and stiffness in various neuromuscular diseases and to provide reference values for different neuromuscular disease groups using a novel handheld non-invasive myometer device MyotonPRO®. We conducted a monocentric blinded cross-sectional study in patients with a set of distinct neuromuscular diseases (NCT04411732, date of registration June 2, 2020). Fifty-two patients in five groups and 21 healthy subjects were enrolled. We evaluated motor function (6-min walk test, handheld dynamometry, Medical Research Council (MRC) Scale) and used ultrasound imaging to assess muscle tissue (Heckmatt scale). We measured muscle stiffness, frequency, decrement, creep, or relaxation using myotonometry with the device MyotonPRO®. Statistically, all values were calculated using the t test and Mann–Whitney U test. No differences were found in comparing the results of myotonometry between healthy and diseased probands. Furthermore, we did not find significant results in all five disease groups regarding myotonometry correlating with muscle strength or ultrasound imaging results. In summary, the myometer MyotonPRO® could not identify significant differences between healthy individuals and neuromuscular patients in our patient collective. Additionally, this device could not distinguish between the five different groups of disorders displaying increased stiffness or decreased muscle tone due to muscle atrophy. In contrast, classic standard muscle tests could clearly decipher healthy controls and neuromuscular patients.
... However, this symmetry is not completely warranted, which is considered a strong risk factor of musculoskeletal injury [4]. cient accuracy and precision of manual myotonometric assessment with MyotonPRO in different tissues and regions [28][29][30][31][32], including PFMs [25,33]. ...
Full-text available
This study aimed to identify if the muscle mechanical properties (MMPs) of both sides of pelvic floor muscles (PFMs) are symmetrical in different populations of both sexes. Between-sides comparisons of MMPs of PFMs, assessed with manual myotonometry, were performed in three groups, with 31 subjects each, composed of healthy nulliparous women (without any type of delivery or pregnancy), multiparous women (with at least two vaginal deliveries), and healthy adult men. Intra-group correlations between MMPs and age, body mass index (BMI), or clinical state of pelvic floor were also obtained. The nulliparous women and the men showed no between-sides differences in any MMP of PFMs. However, the multiparous women showed that the right side displayed less frequency (−0.65 Hz, 95% CI = −1.01, −0.20) and decrement (0.5, 95% CI = 0.11, 0.01), and more relaxation (1.00 ms, 95% CI = 0.47, 1.54) and creep (0.07 De, 95% CI = 0.03, 0.11), than the left side. Further, MMPs were related to age, sex, and BMI, also depending on the population, with the multiparous women being the only group with some between-sides asymmetries, which in this case were positive and of fair intensity for the left side of the PFMs, between BMI, and frequency and stiffness (rho Spearman coefficient: 0.365 and 0.366, respectively). The symmetry of MMPs of the PFMs could depend on the subject’s condition. Multiparous women show a higher tendency to asymmetries than nulliparous women and men, which should be considered in research and clinical settings.
... Currently, the methods mainly used to evaluate muscle condition include isokinetic exercise, muscle activity (EMG), and muscle tone (TMG) [9]. Factors that can be checked using the equipment currently used in rehabilitation medicine include muscle tone, stiffness, elasticity, recovery, and elongation [10][11][12][13]. However, research on muscle elasticity properties conducted to date has only targeted patients with muscle disease or the elderly [14][15][16][17]; it is necessary to expand the scope of studies to various individuals, including adults. ...
Full-text available
(1) Background: The amount of physical activity most adults perform is less than the recommended amount, and the resulting decrease in physical strength makes them vulnerable to various diseases. A decrease in muscle size and strength due to damage caused by disease or aging negatively affects functional strength. Muscle evaluation in adults can yield results that are predictive indicators of aging and unexpected disability. In addition, balance ability is essential to prevent falls and injuries in daily life and maintain functional activities. It is important to develop and strengthen balance in the lower extremities and core muscles to maintain and enhance overall body balance. This study aimed to analyze the effects of core balance training on muscle tone and balance ability in adults. (2) Methods: The participants of this study were 32 adult male and female university students (male: mean age = 21.3 ± 1.9 years, weight = 74.2 ± 12.6 kg, BMI = 23.4 + 2.5, n = 14; female: mean age = 21.0 ± 1.4 years, weight = 64.6 + 1.2 kg, BMI = 22.4 ± 2.4, n =18). Thirty-two adults (training group: 16, control group: 16; male: 16, female: 16) participated in the Myoton PRO (gastrocnemius lateral/medial, tibialis anterior), Pedalo balance system, and Y-balance test. (3) Results: The following results were obtained for muscle elasticity, stiffness, and dynamic/static balance ability after 10 weeks of core balance training. 1. There was no significant difference in muscle elasticity (gastrocnemius lateral/medial, tibialis anterior) (p < 0.05). 2. Muscle stiffness (gastrocnemius lateral/medial, tibialis anterior) significantly increased (p < 0.05). 3. Dynamic/static balance ability significantly increased (p < 0.05). (4) Conclusions: In future, data for the age and sex of various participants, should be accumulated by recruiting participants to study muscle characteristics, such as muscle elasticity and stiffness. Estimating the appropriate injury range and optimal exercise capacity is possible through follow-up studies. The findings can then be used as a basis for predicting injuries or determining and confirming the best time to resume exercise.
Full-text available
Background: Skin is the largest organ in the body, representing an important interface to monitor health and disease. However, there is significant variation in skin properties for different ages, genders and body regions due to the differences in the structure and morphology of the skin tissues. This study aimed to evaluate the use of non-invasive tools to discriminate a range of mechanical and functional skin parameters from different skin sites. Materials and methods: A cohort of 15 healthy volunteers was recruited following appropriate informed consent. Four well-established CE-marked non-invasive techniques were used to measure four anatomical regions: palm, forearm, sole and lower lumbar L3, using a repeated measures design. Skin parameters included trans-epidermal water loss (TEWL), pH (acidity), erythema, stratum corneum hydration and stiffness and elasticity using Myoton Pro (skin and muscle probe). Differences between body locations for each parameter and the intra-rater reliability between days were evaluated by the same operator. Results: The results indicate that parameters differed significantly between skin sites. For the Myoton skin probe, the sole recorded the highest stiffness value of 1006 N/m (SD ± 179), while the lower lumbar recorded the least value of 484 N/m (SD ± 160). The muscle indenter Myoton probe revealed the palm's highest value of 754 N/m (± 108), and the lower lumbar recorded the least value of 208 N/m (SD ± 44). TEWL values were lowest on the forearm, averaging 11 g/m2/h, and highest on the palm, averaging 41 g/m2/h. Similar skin hydration levels were recorded in three of the four sites, with the main difference being observed in the sole averaging 13 arbitrary units. Erythema values were characterised by a high degree of inter-subject variation, and no significant differences between sites or sides were observed. The Myoton Pro Skin showed excellent reliability (intra-class correlation coefficients > 0.70) for all sites with exception of one site right lower back; the Myoton pro muscle probes showed good to poor reliability (0.90-017), the corneometer showed excellent reliability (>0.75) among all the sites tested, and the TEWL showed Good to poor reliability (0.74-0.4) among sites. Conclusion: The study revealed that using non-invasive methods, the biophysical properties of skin can be mapped, and significant differences in the mechanical and functional properties of skin were observed. These parameters were reliably recorded between days, providing a basis for their use in assessing and monitoring changes in the skin during health and disease.
Full-text available
VO2max is considered single best indicator of cardiovascular fitness and aerobic endurance. We analyzed retrospectively, are there any relationships between muscle parameters and oxygen consumption in a study where the myoton equipment was used to establish muscle biomechanical properties, such as elasticity, stiffness, and tension (measured as oscillation frequency) in triathletes. Eight muscles were studied in 14 male triathletes over three years. Relaxed and contracted states of muscles were measured. VO2max was recorded in these athletes up to four times during this period. Average values were calculated for each athlete and High (max 71.8 to min 62.3 ml/kg/min) and Low (59.1 to 51.3) oxygen consumption groups were formed. Higher oxygen consumption correlated significantly (r=-0.58; p=0.029) with improved elasticity (represented by smaller decrement values) of the rectus femoris muscle in a contracted state. Also, in the High VO2max group, this muscle (in a relaxed state) was significantly more elastic and stiffer at the same time compared to the Low group. An ultrasound registration was also conducted to observe the depth of the device's impact in the posterior crural muscles. It was confirmed that deep and substantial tissue disturbances were caused by this impact. According to our findings, myotonometry is an adequate method to establish muscle parameters. Elasticity and stiffness of the rectus femoris muscle may determine success in triathlon.
Full-text available
Background: The relationship between stiffness and drop jump performance in athletes in various stages of development has yet to be fully investigated. The first aim of this study was to investigate the association between the stiffness of the patellar and quadriceps tendon (PT, QT), gastrocnemius-Achilles tendon unit (GAT), and rectus femoris (RF) using drop jump (DJ) performance in young basketball players. The second aim was to investigate possible variations in the stiffness levels of those tissues in different developmental stages. Methods: The stiffness levels of the GAT, PT, QT, and RF were measured in both limbs in 73 male basketball players aged 12 to 18 years. The reactive strength index (RSI), contact time (CT) and jump height (JH) during 30 and 40 cm DJs were also measured. Results: Pearson correlation coefficients showed a significant association between DJ performance and PT, QT, GAT, and RF dynamic stiffness. Moreover, the youngest subjects were found to have lower stiffness values than the older ones. Conclusions: Tissue stiffness can affect athletic performance by modifying the stretch-shortening cycle in young basketball players. Stiffness of muscles and tendons increases during the maturation process. Further investigations could shed light on the effect of training on the stiffness of muscles and tendons.
This study assessed the differences in muscle stiffness of the medial gastrocnemius (MG) and tibialis anterior (TA) muscles at rest and contraction during ovulation and follicular phase (menstruation) in women with regular menstrual cycle. Thirty‐four young healthy women (mean age 21.3 ± 1.3 years) with regular menstrual cycles participated in this study. Stiffness of the TA and MG muscles at rest and voluntary contraction during ovulation and follicular phase in young women were measured using shear‐wave elastography (SWE) and the handheld myotonometer MyotonPRO. The absolute stiffness difference between resting and contraction was expressed as the stiffness increase rate (SIR). The stiffness of the MG and TA at the resting position was not significantly different between the two phases of the menstrual cycle (p > .05). A significantly greater stiffness of both muscles measured using MyotonPRO in the follicular phase than during ovulation was found (p < .05), while stiffness measured by SWE showed a difference only in the TA muscle during contraction (p < .05). In addition, there were no significant differences in the SIR of both muscles between the two phases (p > .05). The results of our study showed a significantly greater stiffness of the MG and TA muscles at the follicular phase than at ovulation during contraction only. As muscle stiffness affects the risk of injury owing to reduced stability during sports activities, these changes in mechanical properties during the menstrual cycle should be noted, and training strategies should be used in female athletes. This article is protected by copyright. All rights reserved.
Full-text available
Usage of the methods of preventive medicine makes it possible to avoid pathological conditions caused by overloads. 15 female gymnasts, going in for artistic gymnastics (age from 10 to 14 years), were under observation during a five-year time period. Changes in linear dimensions of the vertebral column and the biomechanical characteristics of peripheral skeletal muscles were recorded using original biomechanical methods developed at the University of Tartu [18]. The training volume and intensity of the gymnasts' training process were recorded, also the percentage of the elements including impact loads in the daily training. The results of our study show that there exist two immediate reaction types of musculoskeletal system (MSS) in female artistic gymnasts' activities: the positive and the zero reaction. The latter reaction takes place in case the elasticity of muscles of lower extremities has significantly decreased, this creates preconditions for overloading-caused intervertebral discs elasticity decrease.
Full-text available
Single frog skeletal muscle fibers were attached to a servo motor and force transducer by knotting the tendons to pieces of wire at the fiver insertions. Small amplitude, high frequency sinusoidal length changes were then applied during tetani while fibers contracted both isometrically and isotonically at various constant velocities. The amlitude of the resulting force oscillation provides a relative measure of muscle stiffness. It is shown from an analysis of the transient force responses observed after sudden changes in muscle length applied both at full and reduced overlap and during the rising phase of short tetani that these responses can be explained on the basis of varying numbers of cross bridges attached at the time of the length step. Therefore, the stiffness measured by the high frequency legth oscillation method is taken to be directly proportional to the number of cross bridges attached to thin filament sittes. It is found that muscle stiffness measured in this way falls with increasing shortening velocity, but not as rapidly as the force. The results suggest that at the maximum velocity of shortening, when the external force is zero, muscle stiffness is still substantial. The findings are interpreted in terms of a specific model for muscle contraction in which the maximum velocity of shortening under zero external load arises when a force balance is attained between attached cross bridges somr interpretations of these results are also discussed.
Full-text available
Twelve experienced male weight lifters performed a rebound bench press and a purely concentric bench press lift. Data were obtained pertaining to 1) the benefits to concentric motion derived from a prior stretch and 2) the movement frequency adopted during performance of the stretch-shorten cycle (SSC) portion of the rebound bench press lift. The subjects also performed a series of quasi-static muscular actions in a position specific to the bench press movement. A brief perturbation was applied to the bar while these isometric efforts were maintained, and the resulting damped oscillations provided data pertaining to each subject's series elastic component (SEC) stiffness and natural frequency of oscillation. A significant correlation (r = -0.718, P less than 0.01) between maximal SEC stiffness and augmentation to concentric motion derived from prior stretch was observed. Subjects were also observed to perform the SSC portion of the rebound bench press movement to coincide with the natural frequency of oscillation of their SEC. These results are interpreted as demonstrating that the optimal stiffness in a rebound bench press lift was a resonant-compliant SEC.
The human ligamentous lumbar spine was modelled in the frontal plane as an Euler column for the purpose of rigorously studying its mechanical stability. Using stiffness data obtained from testing cadaveric specimens, we simulated the vertebral bodies as rigid links and the intervertebral elastic behaviour as both linear (linear model) and exponential (exponential model). The linear model, with a higher initial stiffness, predicted a higher buckling load (67 N), and hence was more stable in upright posture than the exponential model (11 N). After buckling, the greatest lateral motion was predicted at L5-S1. The exponential model predicted postbuckling motion to be less than 5° at 100 N, while the linear model predicted an excessive 40° at L5-S1. In both models the injured spine, simulated with decreased intervertebral stiffness, was predicted to be more unstable by buckling at lesser loads and undergoing greater postbuckling lateral motion. Validation of this model was accomplished through experimentation described in Part II.
1. The tension in tetanized cat soleus and lateral gastrocnemius muscles was measured during alternating lengthening and shortening movements. Sinusoidal movements were sometimes used; on other occasions the movement was at a constant velocity but with periodic reversal of direction.2. With constant velocity movements of small amplitude the tension rose steeply during lengthening and fell during shortening in a relatively simple way. With longer movements the tension at first changed steeply as it had done with the smaller movement, but later in the movement the resistance of the muscles decreased so that the tension change became more gradual. The muscles resisted a small movement or the first part of a larger movement with a ;short range stiffness' which did not persist as the movement continued.3. So long as the constant velocity movement was not too slow the short range stiffness was independent of velocity though it lasted for more of a fast movement than of a slow one.4. In small movements the muscle was never extended beyond its short range stiffness, and the over-all peak-to-peak tension change was therefore large compared with the amplitude of movement. When, with larger movements, the muscle was stretched into a range in which it became more compliant, the peak-to-peak force fluctuation did not increase by an equivalent amount, and over the whole course of the movement the force change per unit extension was smaller.5. When the movement was confined to a short range, little work was expended in driving the muscle through a cycle of movement; its properties were essentially elastic. With larger amplitudes the muscle met the movement with a frictional resistance, the tension during lengthening then being greater than during shortening. A considerable amount of work had then to be done on the muscle to maintain the movement.6. The short range stiffness was also apparent in the response to sinusoidal movements.7. The short range stiffness was attributed to elastic properties of cross-bridges between thick and thin filaments in the myofibrils.8. The effect of the short range stiffness on the mechanical properties of the limb is discussed.
1. By subdividing ventral roots and supplying stimulating pulses to different groups of motor units in rotation, smooth contractions of soleus could be obtained with low rates of stimulation.2. Isometric tension was recorded with different rates of stimulation, and at different muscle lengths.3. Longitudinal histological sections were cut from muscles fixed at different lengths, and sarcomeres were measured. Mean sarcomere lengths in soleus could then be related to the angle at the ankle.4. At high rates of stimulation the maximum active tension was obtained at a length corresponding to an angle of about 60 degrees at the ankle, and a mean sarcomere length of about 2.8 mu. The isometric tension fell only slightly on shortening the muscle to a length equivalent to 100 degrees , and a mean sarcomere length about 2.3 mu. Further shortening caused a marked fall in tension.5. There was a reciprocal relationship between stimulus rate and muscle length; when the muscle was long low rates of stimulation gave near maximal tension, whereas at short lengths the maximum tension was reached only when the stimulus rate was very high. It is suggested that stimulating pulses activate the contractile machinery of the muscle more effectively at long than at short muscle lengths.6. When at low rates of stimulation pulses were distributed among the motor units in rotation to give a smooth contraction, the tension rose higher than during the unfused tetanus that accompanied synchronous stimulation of the same motor units at the same rate. It is suggested that in an unfused tetanus internal movement of the muscle reduces the tension below that developed in a truly isometric state.7. The rate of rise of tension in an isometric tetanus varied with both muscle length and rate of stimulation. At each stimulus rate there was a range of lengths in which the isometric tension developed slowly, this was the same length range in which, at that stimulus rate, the length tension curve was steep.
We report on a conceptual two degrees of freedom (2 DOF) human gait model, which incorporates nonlinear joint stiffness as a stabilizing agent. Specifically, muscle spring-like property provides inherent stability during gait movement using a nonlinear angular spring and dash pot at each joint. The instability problem of the gait model in direct dynamic analysis is overcome by simulating the human co-contraction muscle function. By developing dynamic system stability requirements and hypothesizing a minimum joint stiffness criterion, we determine time-varying joint stiffness. Optimum joint stiffnesses are present for varying gait pattern, stride lengths and cadences. We conclude that nonlinear joint stiffness can be incorporated into gait models to overcome stability problems inherent in such linkage models.
Stability is the ability of a system to return to its original state after a disturbance. Taking vertical oscillations of the centre of mass of a human bending his legs as an example we prove that the intrinsic mechanical properties of musculature can stabilize the oscillatory movement (preflex) without reflexive changes in activation. The human is represented by a model consisting of a massless two-segment linkage system (knee) topped by a point mass. Conditions for stability are calculated analytically based on the theory of Ljapunov and the results are illustrated by numerical examples. In order to guarantee a self-stabilizing ability of the muscle-skeletal system, the muscle properties such as force-length relationship, force-velocity relationship and the muscle geometry must be tuned to the geometric properties of the linkage system.