Mechanical Stress Relaxation Time Research Articles

The role of muscle function and pointe shoe characteristics in Arabesque movement among ballet dancers with non-specific low back pain

ABSTRACT This study aimed to investigate posterior chain muscle function and the influence of pointe shoes in ballet dancers with and without low back pain (LBP) in the Arabesque. Twenty-nine young professional ballet dancers (17 with LBP and 12 healthy controls) were recruited. Muscle strength and mechanical properties of the erector spinae and hamstrings were assessed. The displacement of centre of mass (COM) during Arabesque under different shoe conditions (R-class, Chacott, and own shoes) was measured with a motion capture system. The LBP group exhibited greater dynamic stiffness and decreased mechanical stress relaxation time in the lateral hamstring compared to the control group. During Arabesque, the LBP group demonstrated significantly greater anterior-posterior displacement of the COM and a larger percentage of time to achieve maximal trunk extension angle. The COM displacement in vertical and medial-lateral directions was smaller in the R-class than in their own shoes. LBP impacts muscle mechanical properties, particularly in the lateral hamstring. The compromised muscle function resulted in a longer time to spinal extension during Arabesque, signifying that reduced trunk control contributed to greater COM displacement. Hence, it is essential to emphasise that evaluating muscle properties and dynamic postural control is imperative for dancers experiencing LBP.

Age and sex differences in the biomechanical and viscoelastic properties of upper limb muscles in middle-aged and older adults: A pilot study

Whether muscle properties gradually change with age and how muscle properties are affected by sex remain unclear. In this study, we investigated the influence of age and sex on the biomechanical and viscoelastic properties of arm muscles in middle-aged and older adults. In this cross-sectional study, 80 healthy participants were divided by sex (male and female), and each sex group, by 10-year age ranges (40–49, 50–59, 60–69, and 70–79 years). Muscle properties, including tone, stiffness, elasticity, and mechanical stress relaxation time, were measured with the MyotonPRO. Our results showed that the muscle tone and elasticity of the deltoid and flexor carpi radialis, and the muscle tone of the flexor carpi ulnaris, were significantly greater in men than in women, whereas the stress relaxation time of the triceps was significantly greater in women than in men. Significantly greater muscle stiffness in the biceps brachii was found in the participants over 50 years old. Less muscle elasticity was found in the deltoid, triceps, and flexor carpi ulnaris in those over 70 years old. In conclusion, age and sex have considerable impacts on upper-limb muscle properties in middle-aged and older adults, which should be taken into consideration when planning health promotion projects.

PSXII-10 Non-invasive measurements of woody and normal condition in broiler breast meat

Abstract Woody Breast (WB) defines a quality issue resulting from a muscle abnormality in chicken meat, which makes the breast meat more rigid and sometimes pale in color with inferior texture. The frequency of this defect in Europe is over 30% and some have argued that similar levels may exist in the United States. Given that chicken with WB are of poor economic value and are discriminated by the consumers, producers face significant economic hardship under the current production paradigm. One of the problems in identifying the biological mechanism responsible for WB is that the occurrence and severity of WB can be only identified after harvest. This study is to investigate the physical characteristics of WB and normal breast (NB) in live chicken using a non-invasive, digital palpation device named as “MyotonPRO®”. This technology provides the measurements of superficial muscles regarding dynamic stiffness (100–1500 N/m; DS), elasticity (0.3–2.5), mechanical stress relaxation time (5–40 ms; MSRT) and ratio of deformation and relaxation time (0.3–2.5; RDRT). One hundred breast meat samples were used in this analysis (WB: 50; NB: 50), which were obtained from a local processing plant one day after harvest and sorted based on WB scoring with the naked eye (0, 1 for NB; 2, 3 for WB). One way ANOVA was used to analyze the data as a statistical model. The least squares means of the following variables were significantly different between WB and NB (P < 0.01): DS (603.4 vs 565.8; N/m), and elasticity (1.40 vs 1.55). However, MSRT and RDRT were not significantly different (P > 0.05). These results collectively show that the non-invasive measurements of WB differ from NB. The degree of muscle hardness in WB can be considered as a trait to be selected, and utilized for the genetic/genomic selection program collecting the measurements before harvest.

Quantifying the Changes of Mechanical and Electrical Properties of Paralyzed Muscle in Survivors With Cervical Spinal Cord Injury.

Background: Survivors with spinal cord injury (SCI) have neuromuscular deficits such as muscle atrophy that lead to functional impairments. This study utilized myotonometry and electrical impedance myography (EIM) to quantitatively evaluate the changes in muscle mechanical properties and compositions after SCI.Methods: This study adopted a cross-sectional design. Eighteen SCI patients and 18 healthy individuals were recruited. The outcome measures were: (1) The myotonometer measured muscle mechanical parameters of oscillation frequency (freq), dynamic stiffness, logarithmic decrement (decr), mechanical stress relaxation time, and indication of creep. (2) The electrical impedance myography measured parameters of resistance (R), reactance (X), and phase angle (θ). (3) muscle strength (maxForce); (4) clinical scales of Manual Muscle Testing (MMT) and modified Ashworth scale (MAS). All outcome measures were compared between the bicep brachii muscle of the weaker side of the SCI group and the non-dominate side of the healthy group. Correlation analysis was performed at quantitative data and clinical scales.Results: Freq, stiffness, and maxForce of the SCI group were significantly lower (p < 0.01) than those of the healthy control. The relaxation time and creep were significantly higher in the SCI group than in the control group. Significant differences of R and Xc were observed between the two groups. Significant correlation was observed between freq, stiffness, and months past injury, and between Xc, creep, and relaxation time.Conclusions: Reduced muscle tone and stiffness might relate to muscle atrophy, and higher relax time and creep may be caused by poor contractile ability. The changes in EIM parameters could indirectly reflect the muscle cell size, and fatty and connective tissue alterations. These findings support the feasibility of myotonometer and EIM to quantify muscle mechanical and intrinsic properties in patients with SCI. The results could facilitate the understanding of neuromuscular changes that are related to functional impairments.

Skin anisotropy: Finding the optimal incision line for volar forearm in males and females

PurposeProper understanding of skin biomechanics, viscoelasticity and investigation of skin tension vectors is necessary to find optimal incision lines. Great tension across a healing wound after any surgical procedure might lead to forming hypertrophic scars. The aim of the study was to investigate tension lines in volar forearm skin in young males and females, in order to ensure best incision line. MethodsFive biomechanical and viscoelastic parameters were measured using a hand-held myotonometer: Oscillation Frequency [Hz], Dynamic Stiffness [N/m], Logarithmic Decrement of tissue's natural oscillation, Mechanical Stress Relaxation Time [ms], and Creep. Measurements were taken in four different directions; Along Forearm, Across Forearm, Along Langer's Line and Across Langer's Line. ResultsSignificant main effects for direction were found for Oscillation Frequency (p < 0.001, η2 = 0.371) [Hz], Dynamic Stiffness (p < 0.001, η2 = 0.522) [N/m], Logarithmic Decrement (p < 0.001, η2 = 0.083), Mechanical Stress Relaxation Time (p < 0.001, η2 = 0.494) [ms] and Creep (p < 0.001, η2 = 0.480). For each parameter except for logarithmic decrement results obtained Along Langers Line and Across Forearm were significantly different to Across Langers Line and Along Forearm (p < 0.001, d = −2.76 – 2.66). Significant main effects for sex were found for logarithmic decrement Along Forearm (p < 0.001, d = 1.698) and Across Langer's Line (p = 0.021, d = 1.697). ConclusionsOur results suggested that optimal incision line for this age group in males and females could potentially be performed diagonally i.e. Across Langer's Line or parallel i.e. Along Forearm to forearm axis. These directions would provide the lowest tension across a healing wound and possibly minimalize the risk of hypertrophic scarring post incision.

Biomechanical and viscoelastic properties of the ankle muscles in men with previous history of ankle sprain

In this study, we aimed to explore the impact of previous history of lateral ankle sprain on the mechanical and viscoelastic properties of the tibialis anterior (TA), peroneus longus (PL) and gastrocnemius lateralis (GL) and medialis (GM) in asymptomatic men. For this purpose, a group of 26 men with previous history of lateral ankle sprain (ASG) and a control group (CG) of 29 healthy counter-parts participated in this study. Tone, stiffness, elasticity and mechanical stress relaxation time were measured using a myotonometer in a single session. Higher tone was noted for TA and GL in ASG as compared to CG (effect size of Cohen’s d = 0.57 [p = 0.04] and 0.59 [p = 0.04], respectively). Further, stiffness was higher in ASG than in CG for TA (d = 0.56; p = 0.04), PL (d = 0.58; p = 0.04) and GL (d = 0.63; p = 0.02). Stress relaxation time was also lower for the ASG compared to the CG for TA (d = 0.61; p = 0.03), PL (d = 0.55; p = 0.04) and GL (d = 0.68; p = 0.02). There were no significant differences between groups in elasticity (p > 0.05). GM experienced no significant changes after ankle sprain in any of the variables (p > 0.05). To conclude, previous history of lateral ankle sprain results in higher TA and GL muscle tone. Likewise, these muscles in addition to PL exhibit less deformation against resistance due to their increased stiffness, thus needing a shorter time to restore to their original shape after deformation.

Intra- and inter-evaluator reliability of the MyotonPRO for the assessment of the viscoelastic properties of caesarean section scar and unscarred skin.

The clinical evaluation of viscoelastic properties of the Caesarean section (C-section) scar, such as stiffness and elasticity, is usually carried out using subjective scales and palpation techniques. There is currently no reliable and valid tool that objectively quantifies these properties. The MyotonPRO could fill this gap. Nineteen healthy women aged between 21 and 40years with C-section scars participated in this reliability study. Two points, one on the scar and one on unscarred skin, were measured four times successively with the MyotonPRO by three independent evaluators on the same day. The intra-class correlation (ICC) coefficients were estimated using a two-factor ANOVA to determine the inter- and intra-rater reliability. The capacity of the MyotonPRO to discriminate the viscoelastic properties of the C-Section scar against unscarred skin was assessed using the Wilcoxon signed rank test. The intra- and inter-rater reliability of the viscoelastic property measurements was good to excellent (ICC 0.99-1.00 and 0.87-0.98, respectively). There was no significant difference between C-section scar and unscarred skin in terms of elasticity (P=.737). Significant differences between C-section scars and unscarred skin tissue were observed for tone (P<.001), stiffness (P<.001), creep (P<.001), and mechanical stress relaxation time (P<.001). The MyotonPRO is a reliable tool for an objective measurement of the viscoelastic properties of the C-section scar and unscarred skin. The MyotonPRO can discriminate the viscoelastic properties of the C-section scar against the unscarred skin, for tone, stiffness, creep and relaxation times, but not for elasticity.

Diagnostic Potential of Five Different Biomechanical Parameters to Detect Sclerotic Cutaneous Graft-Versus-Host Disease

INTRODUCTION Skin sclerosis is a significant cause of morbidity in chronic graft-versus-host disease (cGVHD). The current accepted standard for response assessment is the NIH skin score (0-3 scale) which is based on extent of skin involvement and clinician assessment of degree of sclerosis (superficial vs. deep; movable vs. hidebound). There is an urgent need to develop objective measures of skin sclerosis to enable accurate monitoring of disease. The Myoton device is able in a single rapid measurement to simultaneously measure five biomechanical parameters in soft tissue: dynamic stiffness, mechanical stress relaxation time, tissue oscillation frequency, logarithmic decrement, and creep. Sclerotic cGVHD patients have been shown to have increased skin stiffness, relative to normal individuals, in a small study that lacked post-transplant controls.1 In a cross-sectional study including both cGVHD patients and post-transplant controls, we report the ability to differentiate sclerotic from unaffected post-transplant skin for all five available biomechanical parameters. METHOD Sclerotic cGVHD patients (NIH skin score 2-3) (n=13), post-BMT controls (n=10), and healthy controls (n=14) were measured with the Myoton device modified for skin biomechanical assessment. Each subject was measured on 10 bilateral sites (shin, dorsal forearm, volar forearm, upper arm, shoulder, chest, abdomen, upper back, lower back, calf) for a total of 20 measurement sites. For each of the five biomechanical parameters, the overall value per subject was calculated as the average over all 20 measurement sites. We performed receiver operating characteristic (ROC) and area under the curve (AUC) analyses to compare the diagnostic sensitivity of these parameters. RESULTS Sclerotic cGVHD patients showed significant increases (p&lt;0.05) in stiffness and frequency and decreases (p&lt;0.05) in relaxation time compared to controls. The ROC and AUC analyses revealed that the overall frequency (sensitivity: 91%; specificity: 93%; AUC: 0.92), stiffness (sensitivity: 91%; specificity: 93%; AUC: 0.92), and relaxation time (sensitivity: 100%; specificity: 82%; AUC: 0.85) allow for high accuracy in the differentiation of sclerotic patients from post-BMT controls. Multivariate analysis suggested that stiffness, frequency, and relaxation time provide more value in combination than any parameters alone in the differentiation of sclerotic patients and post-BMT controls. By contrast, decrement and creep likely do not add significant value beyond the other three parameters. The Pearson correlation for each pair of the 3 key parameters (frequency, stiffness, and relaxation time) in post-BMT patients was lowest (R2 = 0.651) for stiffness versus relaxation time, suggesting that this combination provides the highest diagnostic yield. Further, within cGVHD patients, all parameters except decrement were able in univariate analysis to distinguish between a site of affected and unaffected skin on the shin and dorsal forearm (p&lt;0.05). CONCLUSIONS Frequency, stiffness and relaxation time of skin demonstrated high accuracy in the differentiation of sclerotic GVHD patients from post-BMT controls. Larger study is needed to develop a multivariate predictive model based on the combination of stiffness and relaxation time. Prospective longitudinal study is also warranted to assess the ability of the Myoton to monitor progression and treatment response in cGVHD patients as compared to the NIH skin score. ACKNOWLEDGEMENTS This work is partially supported by Career Development Award Number IK2 CX001785 from the United Sates Department of Veterans Affairs Clinical Science R&amp;D (CSRD) Service. REFERENCES: Chen F, Dellalana LE, Gandelman JS, et al. Non-invasive measurement of sclerosis in cutaneous cGVHD patients with the handheld device Myoton: a cross-sectional study. Bone marrow transplantation. 2019; 54(4):616 Disclosures Jagasia: Janssen: Research Funding; Kadmon: Consultancy; Incyte: Consultancy. Tkaczyk:Incyte: Consultancy.

Objective assessment of stiffness in the gastrocnemius muscle in patients with symptomatic Achilles tendons

ObjectivesTo establish quantitative values of stiffness for the gastrocnemius muscle in patients diagnosed with Achilles tendinopathy.DesignCase–control study with a single (cross sectional) time point of patients diagnosed with unilateral Achilles...

Objective assessment of stiffness in Achilles tendinopathy: a novel approach using the MyotonPRO

ObjectivesThe aim of this study was to establish quantitative values for asymptomatic and symptomatic Achilles tendons.DesignCohort study with a single (cross-sectional) time point of patients diagnosed with unilateral Achilles tendinopathy...

Between-day reliability of MyotonPRO for the non-invasive measurement of muscle material properties in the lower extremities of patients with a chronic spinal cord injury

Measuring the muscle properties of patients with spinal cord injuries (SCIs) is important to better understand their biomechanical features. In this study, we sought to evaluate the between-day reliability of MyotonPRO, a handheld device that can measure muscle mechanical properties, and assess whether it is reliable to measure muscle properties over time in patients with SCI. Thirteen men with complete SCIs (age 53.9 ± 6.3 years, height 171.0 ± 5.2 cm, weight 66.1 ± 5.8 kg), and injury levels ranging from L1 to T12, were enrolled. Oscillation frequency; logarithmic decrement; dynamic stiffness; mechanical stress relaxation time; and creep of the biceps femoris, medial and lateral gastrocnemius, rectus femoris, tibialis anterior, and Achilles tendon were measured on consecutive days using MyotonPRO. The intraclass coefficient for most muscles and the Achilles tendon ranged from 0.53 to 0.99 for all parameters. The percentage standard error of the measurement for many parameters in most muscles and the Achilles tendon was less than 10%. Bland-Altman analysis showed a high agreement for all mechanical properties. No significant differences were observed in any muscle or Achilles tendon properties between days (all p > 0.05). These results indicate that the MyotonPRO is reliable for between-day measurements of the mechanical properties of lower limb muscles and Achilles tendon in patients with SCI.

Glucocorticoid-Induced Changes in Rat Skeletal Muscle Biomechanical and Viscoelastic Properties: Aspects of Aging

ObjectivesThe purpose of this study was to estimate the state of tension (tone) and the biomechanical and viscoelastic properties of skeletal muscle in aging rats during the administration of different doses of dexamethasone and to find the relationships among the state of muscle atrophy, muscle strength, and the abovementioned muscle properties. MethodsMuscle state of tension, biomechanical (elasticity, dynamic stiffness) and viscoelastic (mechanical stress relaxation time, Deborah number) properties (using MyotonPRO, Myoton Ltd, Tallinn, Estonia), lean body mass (BM), and hind limb grip strength were measured before and after the administration of a 10-day treatment with dexamethasone 100 μg/100 g BM (young and old group) and 50 μg/100 g BM (old group). ResultsMuscle elasticity (logarithmic decrement) was lower in old animals (1.86 ± 0.03) in comparison with young adult rats (1.38 ± 0.04) (P < .01). After the 10-day treatment with dexamethasone 100 μg/100 g BM, young adult rats had 10% lower muscle elasticity (P < .01). The same dose of dexamethasone in old rats increased tone (frequency of natural oscillation) from 29.13 ± 0.51 Hz to 38.50 ± 0.95 Hz (P < .001). There were dose-dependent differences in dynamic stiffness and tone of muscle; changes in elasticity were independent of the dose in old animals. In old rats, the muscle’s viscoelastic properties decreased after dexamethasone administration. Significant correlation was found between changes in muscle logarithmic decrement and stiffness (rs = 0.90; P < .05) in old animals. ConclusionsBiomechanical and viscoelastic properties of skeletal muscle indicate changes in the main function of muscle during glucocorticoid-induced muscle atrophy and are in agreement with changes in hind limb strength. The myometric measurements indicate the direction and magnitude of change in muscle tissue after different doses of dexamethasone administration easily and quickly.

Effect of MELT method on thoracolumbar connective tissue: The full study

Altered connective tissue structure has been identified in adults with chronic low back pain (LBP). A self-care treatment for managing LBP is the MELT method. The MELT method is a hands-off, self-treatment that is said to alleviate chronic pain, release tension and restore mobility, utilizing specialized soft treatments balls, soft body roller and techniques mimicking manual therapy. The objective of this study was to determine whether thickness of thoracolumbar connective tissue and biomechanical and viscoelastic properties of myofascial tissue in the low back region change in subjects with chronic LBP as a result of MELT. This study was designed using a quasi experimental pre-post- design that analyzed data from subjects who performed MELT. Using ultrasound imaging and an algorithm developed in MATLAB, thickness of thoracolumbar connective tissue was analyzed in 22 subjects. A hand-held digital palpation device, called the MyotonPRO, was used to assess biomechanical properties such as stiffness, elasticity, tone and mechanical stress relaxation time of the thoracolumbar myofascial tissue. A forward bending test assessing flexibility and pain scale was added to see if MELT affected subjects with chronic LBP. A significant decrease in connective tissue thickness and pain was observed in participants. Significant increase in flexibility was also recorded.