Feasibility of monitoring muscle health in microgravity environments using Myoton technology

mTG-Gelatin phantoms as standardized testbeds for skin biomechanical measurements with Myoton

Quantitative assessment of skin mechanical properties can play a pivotal role in diagnosing and tracking various dermatological conditions. Myoton is a promising tool that rapidly and noninvasively measures five skin biomechanical parameters. Accurate interpretation of these parameters requires systematic in vitro testing with easy-to-fabricate, cost-effective skin-mimicking phantoms with controllable properties. In this study, we assessed the ability of phantoms made with 5% and 10% gelatin crosslinked with microbial transglutaminase (mTG) to mimic the human skin for Myoton measurements. We discovered that each of the five Myoton parameters displayed moderate to high correlations with shear elastic modulus of the phantoms. Furthermore, Myoton effectively tracked changes in the mechanical properties of these models over time. Additionally, we designed bilayer phantoms incorporating both dermis and subcutaneous tissue-mimicking layers. Myoton successfully distinguished changes in the mechanical properties of the bilayer phantoms due to the introduction of a stiff 2 mm top layer. We also found that 5% mTG-gelatin phantoms mimic Myoton measurements from healthy subjects and 10% phantoms mimic patients with sclerotic chronic graft-versus-host disease (cGVHD). Therefore, multi-layered mTG-gelatin models for skin and soft tissues can serve as standardized testbeds to study different sclerotic skin conditions in a systematic manner.

Applicability of non-invasive, digital palpation device to detection of woody breast conditions in chicken breast muscle

Woody breast (WB) is one of muscle myopathy found in chicken breast, characterized with enlarged size and extremely stiff texture. The WB condition is one of the most prevalent quality issues in the modern poultry industry. WB has been shown to be heritable, but no effective detection method of WB severity in live birds exists for the selection purpose. The objective of this study was to determine potential of a non-invasive, portable digital palpation device as WB detection method that can be used for the selection to estimate the heritability of WB. The physical and functional properties of WB was also investigated in comparison with normal breast (NB). Two hundred ten breast muscles were obtained from a local processing plant one day after harvest and sorted based on WB scoring (1 for NB and 2 and 3 for WB). The samples were subjected to physical and physicochemical analyses, determining biomechanical properties (muscle tone, stiffness, elasticity, relaxation, and creep), pH, color, cooking yield, and texture (firmness and compression energy were used for raw meat and shear force and energy for cooked meat). The least squares means of the following variables were significantly different between WB and NB (p < 0.01): stiffness (603.4 vs 565.8; N/m), and elasticity (1.40 vs 1.55). However, relaxation and creep were not significantly different (p > 0.05). These results collectively showed that biomechanical properties of WB differ from NB. The degree of muscle stiffness in WB can be considered as a trait to be selected. The WB score showed strong negative correlations with cooking yield (-0.77) and cooked L*(-0.74), which means that as the breast becomes harder, the cooking yield decreases, and the color becomes darker after cooking. The WB score showed high correlations with physical and functional characteristics and exhibited strong correlations with the biomechanical properties measured by the device. Therefore, the results indicated that the digital palpation device has potential to detect the WB severity (degree of stiffness) of breast muscle.

Effects of radial extracorporeal shock wave therapy on flexor spasticity of the upper limb in post-stroke patients: A randomized controlled trial

OBJECTIVE

This study aimed to assess the efficacy of radial extracorporeal shock wave therapy in treating upper limb spasticity after a stroke.

DESIGN

Randomized controlled trial.

SETTING

Zhujiang Hospital of Southern Medical University.

SUBJECTS

This study included 95 people with stroke.

INTERVENTION

The active (n = 47) and sham-placebo (n = 48) radial extracorporeal shockwave therapy groups received three treatment sessions (every third day).

MAIN MEASURES

The Modified Ashworth Scale, Hmax/Mmax ratio, root mean square, co-contraction ratio, mechanical parameters of the muscle and temperature were measured at baseline and days 2, 5 and 8.

RESULTS

Among the 135 potential participants screened, 100 were enrolled and allocated randomly, with 95 participants ultimately being included in the intent-to-treat analysis dataset. The active group showed significantly better improvements in upper limb spasticity and muscle function than did the sham-placebo group. Greater improvements in the Modified Ashworth Scale were observed in the active group than in the sham-placebo group (difference, -0.45; 95% CI, -0.69 to -0.22; P < 0.001). Moreover, significant differences in root mean square, co-contraction ratio and Hmax/Mmax ratio were observed between the two groups (all P < 0.001). The mechanical parameters of the biceps muscle were significantly better in the active group than in the sham-placebo group (P < 0.001). The active group had a higher temperature than the sham-placebo group, although the difference was not significant (P = 0.070).

CONCLUSIONS

This study revealed that the treatment with extracorporeal shockwave therapy can relieve upper limb spasticity in people with stroke.

Exploratory Study of Biomechanical Properties and Pain Sensitivity at Back-Shu Points

OBJECTIVES

Hypersensitive acupoints in specific body areas are associated with corresponding internal or visceral disorders. Back-shu points are clinically significant for the diagnosis of visceral organ disease, according to the biomechanical characteristics of the acupoints. In this study, we assessed the biomechanical characteristics and pain sensitivities of five back-shu points linked to five visceral organs in healthy participants.

METHODS

The study included 48 volunteer participants. A myotonometry was used to assess muscle tone and muscle stiffness at five back-shu points associated with visceral organs. Pressure was monitored using a microcontroller and a force sensor. Pain sensitivity was assessed in response to deep pressure pain produced by a constant force.

RESULTS

Substantial differences in muscle tone and stiffness were observed at the five back-shu points; muscle tone was highest at BL15, whereas muscle tone and muscle stiffness were lowest at BL23. Moreover, pain sensitivity was significantly different among the acupoints; pain sensitivity was highest at BL23. There was a significant negative correlation between muscle tone and pain sensitivity.

CONCLUSIONS

We found significant differences in muscle tone, muscle stiffness, and pain sensitivity among five back-shu points associated with visceral organs, which may be attributable to anatomical variations at each point. Our findings suggest that differences at back-shu points should be considered to ensure the accurate diagnosis of visceral disease.

MyotonPRO as a new valid tool for measuring cervical muscle tension. A reliability study

OBJECTIVE

The main objective of this study is to test the reliability of a non-invasive objective method for the measurement of biomechanical parameters of cervicofacial muscle groups, with the purpose of diagnosis and evaluation of voice disorders' treatments, especially focused on muscle tension dysphonia.

STUDY DESIGN

Prospective study.

METHODS

The device used is a handheld myotonometer (MyotonPRO) that measures biomechanical and viscoelastic properties in superficial soft tissues frequency, stiffness, elasticity, relaxation time and creep. It is used in the field of medicine, sport and research. This pilot study includes 10 subjects, who have been measured in the masseter, sternocleidomastoid, orbicularis oris, semispinalis capitis, suprahyoid, infrahyoid and trapezius muscles on each side. Measurements were performed by 2 evaluators to assess inter-evaluator reliability. Subsequently, one of them repeated the measurements to assess intra-evaluator reliability.

RESULTS

The results revealed good to excellent inter-rater reliability for the masseter, sternocleidomastoid, trapezius and suprahyoid muscles, with lower ICCs for the stiffness and creep properties. Intra-rater reliability was good to excellent for the masseter, sternocleidomastoid, semispinalis capitis and suprahyoid muscles. The lowest ICCs were found in the stiffness and creep properties.

CONCLUSION

The use of a myotonometer to measure the mechanical properties of selected cervical and orofacial muscles is a reliable and reproducible method. Future research is needed to establish an association between the properties of these muscles and their role in voice disorders, as well as to determine whether this tool can aid diagnosis with quantifiable and objectifiable indicators, and for monitoring and treatment efficacy.

Regional variations and sex-related differences of stiffness in human tracheal ligaments

PURPOSE

There have been numerous studies focused on the stiffness of tracheal cartilage. However, no research has been conducted specifically on the annular ligament, nor have any regional differences in the annular ligament been identified. The purpose of this study was to investigate the stiffness of the ligaments present between the thyroid, cricoid and tracheal cartilages.

METHODS

The ligaments were identified in the cervical region of living subjects with ultrasonography. The stiffness of the ligaments was measured from the body surface using a digital palpation device (MyotonPRO). Since it is impossible to measure the entire trachea in a living subject, an additional measurement was performed on human cadavers.

RESULTS

Both in vivo and cadaveric investigations found that the stiffness of annular ligaments decreased gradually from the superior to inferior parts. There was no difference in the stiffness between males and females in the superior part of the trachea. However, the stiffness of the middle and inferior parts was predominantly higher in females than in males. Furthermore, males showed significant differences in stiffness between the superior and middle parts, while females showed no significant differences.

CONCLUSION

These results reveal that there are regional and sex-related differences in the stiffness of human tracheal ligaments.

The Myometric Assessment of Achilles Tendon and Soleus Muscle Stiffness before and after a Standardized Exercise Test in Elite Female Volleyball and Handball Athletes-A Quasi-Experimental Study

Background: The high prevalence of injuries in female athletes necessitates a course of action that not only enhances research in this field but also incorporates improved prevention programs and regular health monitoring of highly stressed structures such as tendons and muscles. Since myometry is already used by coaches and physiotherapists, it is important to investigate whether tissue stiffness varies in different types of sports, and whether such measures are affected by an acute training session. Methods: Myometric measurements of the Achilles tendon (AT) and soleus muscle (SM) were performed in the longitudinal plane and relaxed tendon position. In total, 38 healthy professional female athletes were examined, applying a quasi-experimental study design, with subgroup analysis performed for different sports. To investigate the stiffness of the AT and SM, 24 female handball and volleyball athletes performed a standardized maximal incremental performance test on a treadmill. In this subgroup, myometric measurements were taken before and after the exercise test. Results: The measurements showed no significant difference between the mean pre- (AT: 661.46 N/m; SM 441.48 N/m) and post-exercise stiffness (AT: 644.71 N/m; SM: 439.07 N/m). Subgroup analysis for different types of sports showed significantly lower AT and SM stiffness in swimming athletes compared to handball (p = 0.002), volleyball (p = 0.000) and hammer throw athletes (p = 0.008). Conclusions: Myometry can be performed on the same day as an acute training session in healthy female professional volleyball and handball athletes. Female swimmers have significantly lower AT and SM stiffness compared to female handball, volleyball and hammer throw athletes. These results show that the stiffness differences in the AT and SM can be assessed by myometry.

Changes in the mechanical properties of the thigh and lower leg muscle-tendon units during the early follicular and early luteal phases

Background

This study aimed to determine changes in the muscle and tendon stiffness of the thigh and lower leg muscle-tendon units during the early follicular and early luteal phases, and check for possible relations between muscle and tendon stiffness in each phase.

Methods

The sample consisted of 15 female university students with regular menstrual cycles. The basal body temperature method, ovulation kit, and salivary estradiol concentration measurement were used to estimate the early follicular and early luteal phases. A portable digital palpation device measured muscle-tendon stiffness in the early follicular and early luteal phases. The measurement sites were the rectus femoris (RF), vastus medialis (VM), patellar tendon (PT), medial head of gastrocnemius muscle, soleus muscle, and Achilles tendon.

Results

No statistically significant differences in the thigh and lower leg muscle-tendon unit stiffness were seen between the early follicular and early luteal phases. Significant positive correlations were found between the stiffness of the RF and PT (r = 0.608, p = 0.016) and between the VM and PT (r = 0.737, p = 0.002) during the early luteal phase.

Conclusion

The present results suggest that the stiffness of leg muscle-tendon units of the anterior thigh and posterior lower leg do not change between the early follicular and early luteal phases and that tendons may be stiffer in those women who have stiffer anterior thigh muscles during the early luteal phase.

Muscle stiffness indicating mission crew health in space

Muscle function is compromised by gravitational unloading in space affecting overall musculoskeletal health. Astronauts perform daily exercise programmes to mitigate these effects but knowing which muscles to target would optimise effectiveness. Accurate inflight assessment to inform exercise programmes is critical due to lack of technologies suitable for spaceflight. Changes in mechanical properties indicate muscle health status and can be measured rapidly and non-invasively using novel technology. A hand-held MyotonPRO device enabled monitoring of muscle health for the first time in spaceflight (> 180 days). Greater/maintained stiffness indicated countermeasures were effective. Tissue stiffness was preserved in the majority of muscles (neck, shoulder, back, thigh) but Tibialis Anterior (foot lever muscle) stiffness decreased inflight vs. preflight (p < 0.0001; mean difference 149 N/m) in all 12 crewmembers. The calf muscles showed opposing effects, Gastrocnemius increasing in stiffness Soleus decreasing. Selective stiffness decrements indicate lack of preservation despite daily inflight countermeasures. This calls for more targeted exercises for lower leg muscles with vital roles as ankle joint stabilizers and in gait. Muscle stiffness is a digital biomarker for risk monitoring during future planetary explorations (Moon, Mars), for healthcare management in challenging environments or clinical disorders in people on Earth, to enable effective tailored exercise programmes.

Acute effects of muscle mechanical properties after 2000-m rowing in young male rowers

Background

The mechanical properties of muscles, such as changes in muscle tone and stiffness, are related to sports performance and injuries. Rowers are at increased risk of muscle fatigue and injury during high-repetition and heavy-load cyclic muscle actions. In view of this, the aim of the present study was to investigate the acute effect on muscle tone and stiffness, as well as bilateral muscle asymmetry, in high school rowers after a 2000-meter rowing ergometer test.

Methods

Twelve young male rowers (age = 17.1 ± 0.9 years, body weight = 73.5 ± 9.7 kg) were included in the study. The data of muscle tone (frequency) and stiffness of the posterior deltoids (PD), latissimus dorsi (LD), and rectus femoris (RF) (dominant and non-dominant side) before and after a 2000-m rowing ergometer test were collected using a handheld MyotonPRO device.

Results

After the rowing ergometer test, the muscle tone of dominant side PD, LD, and RF were significantly increased (p < 0.05). On the other hand, the muscle stiffness of the non-dominant side LD and RF, as well as the dominant side PD, LD, and RF were significantly increased after the rowing ergometer test (p < 0.05). The muscle tone and stiffness results showed that the dominant side PD, LD, and RF were all significantly higher than the non-dominant side after the rowing ergometer test (p < 0.05), where bilateral PD and RF exhibits moderate asymmetry (5% < symmetry index < 10%).

Conclusions

After a high-intensity and high-load 2000-m rowing ergometer test, PD, LD, and RF showed increases in muscle tone and stiffness, as well as changes in the symmetry of bilateral muscle mechanical properties.

Space nutrition and the biochemical changes caused in Astronauts Health due to space flight: A review

Astronauts required food that is healthy, nutritious, and tasted good, while also meeting their dietary needs. To ensure the astronauts' nutritional needs are met, a Nutritional Status Assessment Supplemental Medical Objective (Nutrition SMO) is conducted. This involves collecting blood and urine samples from the astronauts, which are then tested and analysed. The assessment looks for indications of bone health, muscle loss, hormonal imbalances, gastrointestinal functions, cardiovascular health, iron metabolism, ophthalmic changes, and immune changes that occur during space flight under conditions of microgravity or weightlessness. It was discovered that iron levels in astronauts tend to increase due to the decrease in body volume during space flight. It requires skilful optimization considering nutrient delivery, shelf life, and packaging of space food, while minimizing resource usage and ensuring reliability, safety, and addressing the physiological and psychological effects on the crew members.

Interrater reproducibility of the Myoton and durometer devices to quantify sclerotic chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is a severe complication in long-term survivors of allogeneic hematopoietic stem cell transplantation. This disease is challenging to manage clinically due to a lack of validated tools to quantitatively measure skin sclerosis. The current gold standard for measuring skin sclerosis is the NIH Skin Score which has only moderate agreement among clinicians and experts. To more accurately assess skin sclerosis in cGVHD, the Myoton and durometer devices can be used to directly measure biomechanical parameters of the skin. However, the reproducibility of these devices is not known in patients with cGVHD. To determine this reproducibility, three observers independently measured 10 anatomic sites in each of seven patients with sclerotic cGVHD using the Myoton and durometer. Clinical reproducibility was measured by mean pairwise differences (U-statistic) and intraclass correlation coefficients (ICCs) with 95% confidence intervals (CIs). Mean pairwise differences, expressed in true physical units, were used to report typical errors for each anatomic site and device. Mean pairwise differences were less than 11% of the average overall values for all five Myoton parameters and durometer hardness. These were lower for Myoton creep (4.1%), relaxation time (4.7%), and frequency (5.1%) than decrement (9.0%), stiffness (10.4%), and durometer hardness (9.0%). Myoton parameters creep, relaxation time, and frequency showed promise for capturing skin biomechanics more accurately than Myoton stiffness, decrement, or durometer hardness. Mean pairwise differences trended highest in the shin and volar forearm and lowest in the dorsal forearm. The interobserver ICC for overall (averaged across all measured body sites of a patient) creep (0.94; 95% CI 0.87-1.00), relaxation time (0.96; 95% CI 0.90-1.00), and frequency (0.95; 95% CI 0.88-1.00), trended higher than that for decrement (0.43; 95% CI 0.00-0.88), stiffness (0.92; 95% CI 0.81-1.00), and durometer hardness (0.82; 95% CI 0.61-1.00). Similar trends were observed in healthy participants. These findings can help clinicians design better studies to assess therapeutic response to new cGVHD treatments and support the interpretation of future measurements.

Relationship Between Achilles Tendon Stiffness Using Myoton PRO and Translation Using a Tensile Testing Machine: A Biomechanical Study of a Porcine Model

Background Achilles tendinopathy is a common ankle disorder in both the general population and athletes. This condition can alter the mechanical characteristics of the Achilles tendon (AT) by decreasing tendon stiffness. Achilles tendinopathy is primarily treated conservatively; however, few monitoring tools exist for evaluating the condition of the AT. The Myoton PRO (Myoton AS, Tallinn, Estonia) device is a handheld tool used to evaluate tissue stiffness. However, no basic studies have examined the validity of Myoton PRO for assessing the AT. This study aimed to assess the validity of Myoton PRO using animal ATs and to examine its clinical applicability. Methods We used 28 fresh porcine ankles and evaluated AT stiffness at the calcaneus insertion site (AT0) and 2.0 cm above the calcaneus (AT2) using Myoton PRO. We also measured changes in the AT length using a tensile testing machine during the cyclic loading test. We investigated the correlation between dynamic stiffness and length change. Furthermore, we assessed the difference in stiffness between AT0 and AT2. Results The dynamic stiffness was 717.6 ± 183.1 N/m at AT0 and 467.4 ± 152.3 N/m at AT2. The change in length during the cyclic loading test was 1.8 ± 0.7 mm. The correlation between dynamic stiffness and length change was as follows: AT0, r=-0.61; AT2, r=-0.64 (P<0.001). The dynamic stiffness at AT0 was significantly greater than that at AT2 (P<0.001). Conclusions AT assessment using Myoton PRO has potential clinical utility as an indicator of tissue stiffness.

Dynamic Correlations and Disorder in the Masticatory Musculature Network

BACKGROUND

Temporomandibular joint (TMJ) disorders, which affect millions of people worldwide, have multiple etiological factors that make an accurate diagnosis and effective treatments difficult. As a consequence, the gold standard diagnostic criteria for TMJ disorders remain elusive and often depend on subjective decisions.

AIM

In this context, the lack of a non-invasive quantitative methodology capable of assessing the functional physiological state and, consequently, identifying risk indicators for the early diagnosis of TMJ disorders must be tackled and resolved.

METHODOLOGY

In this work, we have studied the biomechanics and viscoelastic properties of the functional masticatory system by a non-invasive approach involving 52 healthy subjects, analysed by statistical-physics analysis applied to myotonic measurements on specific points of the masticatory system designing a TMJ network composed of 17 nodes and 20 links.

RESULTS

We find that the muscle tone and viscoelasticity of a specific cycle linking frontal, temporal, and mandibular nodes of the network play a prominent role in the physiological functionality of the system. At the same time, the functional state is characterised by a landscape of nearly degenerated levels of elasticity in all links of the network, making this parameter critically distributed and deviating from normal behaviour.

CONCLUSIONS

Time evolution and dynamic correlations between biomechanics and viscoelastic parameters measured on the different cycles of the network provide a quantitative framework associated with the functional state of the masticatory system. Our results are expected to contribute to enriching the taxonomy of this system, primarily based on clinical observations, patient symptoms, and expert consensus.

Objective Methods of Muscle Tone Diagnosis and Their Application-A Critical Review

"Muscle tone" is a clinically important and widely used term and palpation is a crucial skill for its diagnosis. However, the term is defined rather vaguely, and palpation is not measurable objectively. Therefore, several methods have been developed to measure muscle tone objectively, in terms of biomechanical properties of the muscle. This article aims to summarize these approaches. Through database searches, we identified those studies related to objective muscle tone measurement in vivo, in situ. Based on them, we described existing methods and devices and compared their reliability. Furthermore, we presented an extensive list of the use of these methods in different fields of research. Although it is believed by some authors that palpation cannot be replaced by a mechanical device, several methods have already proved their utility in muscle biomechanical property diagnosis. There appear to be two issues preventing wider usage of these objective methods in clinical practice. Firstly, a high variability of their reliability, and secondly, a lack of valid mathematical models that would provide the observed mechanical characteristics with a clear physical significance and allow the results to be compared with each other.

Lunar and mars gravity induce similar changes in spinal motor control as microgravity

Introduction: Once more, plans are underway to send humans to the Moon or possibly even to Mars. It is therefore, important to know potential physiological effects of a prolonged stay in space and to minimize possible health risks to astronauts. It has been shown that spinal motor control strategies change during microgravity induced by parabolic flight. The way in which spinal motor control strategies change during partial microgravity, such as that encountered on the Moon and on Mars, is not known. Methods: Spinal motor control measurements were performed during Earth, lunar, Mars, and micro-gravity conditions and two hypergravity conditions of a parabola. Three proxy measures of spinal motor control were recorded: spinal stiffness of lumbar L3 vertebra using the impulse response, muscle activity of lumbar flexors and extensors using surface electromyography, and lumbar curvature using two curvature distance sensors placed at the upper and lower lumbar spine. The participants were six females and six males, with a mean age of 33 years (standard deviation: 7 years). Results: Gravity condition had a statistically significant (Friedmann tests) effect spinal stiffness (p < 0.001); on EMG measures (multifidus (p = 0.047), transversus abdominis (p < 0.001), and psoas (p < 0.001) muscles) and on upper lumbar curvature sensor (p < 0.001). No effect was found on the erector spinae muscle (p = 0.063) or lower curvature sensor (p = 0.170). Post hoc tests revealed a significant increase in stiffness under micro-, lunar-, and Martian gravity conditions (all p's < 0.034). Spinal stiffness decreased under both hypergravity conditions (all p's ≤ 0.012) and decreased during the second hypergravity compared to the first hypergravity condition (p = 0.012). Discussion: Micro-, lunar-, and Martian gravity conditions resulted in similar increases in spinal stiffness, a decrease in transversus abdominis muscle activity, with no change in psoas muscle activity and thus modulation of spinal motor stabilization strategy compared to those observed under Earth's gravity. These findings suggest that the spine is highly sensitive to gravity transitions but that Lunar and Martian gravity are below that required for normal modulation of spinal motor stabilization strategy and thus may be associated with LBP and/or IVD risk without the definition of countermeasures.

Sensory and emotional responses to deep pressure stimulation at myofascial trigger points: a pilot study

Objective

Although manual pressure, such as that used during a massage, is often associated with pain, it can simultaneously be perceived as pleasant when applied to certain body areas. We hypothesized that stimulation of myofascial trigger points (TPs) leads to simultaneous pain and pleasure. TPs are hyperirritable points located in the taut band of the skeletal muscle.

Method

In this study, we measured the muscle tone, muscle stiffness, and pressure pain threshold of TPs and control points in the left brachioradialis muscle of 48 healthy participants. We also applied deep compression to the two points and collected subjective data on pain, pleasantness, unpleasantness, and relief.

Result

Greater muscle stiffness was observed in the TPs versus control points (t = 6.55, p < 0.001), and the pain threshold was significantly lower in the TPs (t = -6.21, p < 0.001). Unpleasantness ratings after deep compression were significantly lower in the TPs compared with control points (t = -2.68, p < 0.05). Participants experienced greater relief at the TPs compared with control points (t = 2.01, p < 0.05), although the perceived pain did not differ between the two types of points.

Conclusion

We compared the properties of TPs and control points, and found that deep compression at TPs was associated with higher muscle tone and stiffness, lower unpleasantness ratings, and higher relief ratings compared with the control points. These findings suggest that, at least for some TPs, pain and pleasantness are simultaneously elicited by deep pressure stimulation.

Quantification of the forearm muscles mechanical properties using Myotonometer: Intra- and Inter-Examiner reliability and its relation with hand grip strength

The primary objective of this study was to investigate the reliability of the myotonometer in the mechanical properties of the forearm muscles [m. extensor carpi radialis brevis (ECRB), and m. flexor carpi ulnaris (FCU)] in healthy individuals. The secondary objective was to investigate the relationship between the handgrip strength and mechanical properties of these forearm muscles. The mechanical properties (muscle tone, stiffness, and elasticity) of the ECRB and FCU were measured using the MyotonPRO device. Examiner 1 performed two sets of measurements with a time interval of 30 min to determine intra-examiner reliability. Examiner 2 performed measurements during the interval between the two sets of examiner 1. The intra- and inter-examiner reliabilities were excellent (ICC˃0.82) for muscle tone, stiffness, and elasticity of the FCU. Both intra- and inter-examiner reliability in the evaluation of ECRB muscle tone, elasticity, and stiffness was moderate to excellent (ICCs = 0.56-0.98). The muscle tone and stiffness properties of the FCU were positively correlated with the handgrip strength (p <.05). The study findings indicate that the MyotonPRO device is a reliable tool to quantify ECRB, and FCU muscles mechanical properties in healthy individuals.

Dry immersion induced acute low back pain and its relationship with trunk myofascial viscoelastic changes

Microgravity induces spinal elongation and Low Back Pain (LBP) but the pathophysiology is unknown. Changes in paraspinal muscle viscoelastic properties may play a role. Dry Immersion (DI) is a ground-based microgravity analogue that induces changes in m. erector spinae superficial myofascial tissue tone within 2 h. This study sought to determine whether bilateral m. erector spinae tone, creep, and stiffness persist beyond 2 h; and if such changes correlate with DI-induced spinal elongation and/or LBP. Ten healthy males lay in the DI bath at the Institute of Biomedical Problems (Moscow, Russia) for 6 h. Bilateral lumbar (L1, L4) and thoracic (T11, T9) trunk myofascial tone, stiffness and creep (MyotonPRO), and subjective LBP (0-10 NRS) were recorded before DI, after 1h, 6 h of DI, and 30min post. The non-standing spinal length was evaluated on the bath lifting platform using a bespoke stadiometer before and following DI. DI significantly modulated m. erector spinae viscoelastic properties at L4, L1, T11, and T9 with no effect of laterality. Bilateral tissue tone was significantly reduced after 1 and 6 h DI at L4, L1, T11, and T9 to a similar extent. Stiffness was also reduced by DI at 1 h but partially recovered at 6 h for L4, L1, and T11. Creep was increased by DI at 1 h, with partial recovery at 6 h, although only T11 was significant. All properties returned to baseline 30 min following DI. Significant spinal elongation (1.17 ± 0.20 cm) with mild (at 1 h) to moderate (at 6 h) LBP was induced, mainly in the upper lumbar and lower thoracic regions. Spinal length increases positively correlated (Rho = 0.847, p = 0.024) with middle thoracic (T9) tone reduction, but with no other stiffness or creep changes. Spinal length positively correlated (Rho = 0.557, p = 0.039) with Max LBP; LBP failed to correlate with any m. erector spinae measured parameters. The DI-induced bilateral m. erector spinae tone, creep, and stiffness changes persist beyond 2 h. Evidence of spinal elongation and LBP allows suggesting that the trunk myofascial tissue changes could play a role in LBP pathogenesis observed in real and simulated microgravity. Further study is warranted with longer duration DI, assessment of IVD geometry, and vertebral column stability.

Evaluation of muscle stiffness in adhesive capsulitis with Myoton PRO

Background

Adhesive capsulitis (AC) is characterized by pain and limited range of motion, caused by stiffness of the joint capsule and coracohumeral ligament. On the other hand, there have been few reports on muscle stiffness in AC. The purpose of this study was to assess muscle stiffness in patients of AC with a portable and noninvasive device, Myoton PRO. We hypothesized that muscle stiffness around shoulder joint increases in AC.

Methods

At first, we surveyed correlation between Myoton PRO and shear wave elastography with phantoms. Second, reproducibility and repeatability of healthy volunteers with Myoton PRO were evaluated. Finally, muscle stiffness was measured in 40 patients who were diagnosed with AC. Muscle stiffness was quantitatively measured with Myoton PRO. We compared the stiffness of the anterior deltoid (AD), pectoralis major, and latissimus dorsi (LD) in AC patients on both the affected and nonaffected sides.

Results

Correlation coefficient in shear wave elastography and Myoton PRO was 0.99(P = .001). Reliability of intraoperator and interoperator with Myoton PRO was 0.9 or higher. Muscle stiffness values (N/m) of the AD, pectoralis major, and LD were 355 ± 61, 252 ± 54, 207 ± 51 in the affected sides and 328 ± 50, 252 ± 41, 186 ± 37 in the nonaffected sides, and the differences were significant in the AD and LD (P = .005, P = .002, respectively).

Conclusions

We used Myoton PRO to evaluate muscle stiffness in AC. The AD and LD muscles of AC patients were significantly stiffer on the affected side compared to the nonaffected side.

Soleus muscle and Achilles tendon compressive stiffness is related to knee and ankle positioning

Changes in fascicle length and tension of the soleus (SOL) muscle have been observed in humans using B-mode ultrasound to examine the knee from different angles. An alternative technique of assessing muscle and tendon stiffness is myometry, which is non-invasive, accessible, and easy to use. This study aimed to estimate the compressive stiffness of the distal SOL and Achilles tendon (AT) using myometry in various knee and ankle joint positions. Twenty-six healthy young males were recruited. The Myoton-PRO device was used to measure the compressive stiffness of the distal SOL and AT in the dominant leg. The knee was measured in two positions (90° of flexion and 0° of flexion) and the ankle joint in three positions (10° of dorsiflexion, neutral position, and 30° of plantar flexion) in random order. A three-way repeated-measures ANOVA test was performed. Significant interactions were found for structure × ankle position, structure × knee position, and structure × ankle position × knee position (p < 0.05). The AT and SOL showed significant increases in compressive stiffness with knee extension over knee flexion for all tested ankle positions (p < 0.05). Changes in stiffness relating to knee positioning were larger in the SOL than in the AT (p < 0.05). These results indicate that knee extension increases the compressive stiffness of the distal SOL and AT under various ankle joint positions, with a greater degree of change observed for the SOL. This study highlights the relevance of knee position in passive stiffness of the SOL and AT.

Effect of Modulated Electromyostimulation on the Motor System of Elderly Neurological Patients. Pilot Study of Russian Currents Also Known as Kotz Currents

In this brief report, we present preliminary findings from a study of the use of electromyostimulation (EMS) in neurological patients. Assuming the approach to be sufficiently effective, we decided to investigate the motor system of elderly neurological patients before and after a course of Russian currents EMS, which were developed for Soviet athletes and cosmonauts. To this point, 19 patients—EMS (n = 11) and control (n = 8)—have successfully completed the study. The study included patients aged 60–90 years with confirmed walking and balance disorders with a history of chronic cerebral ischemia. Patients in the experimental group underwent a course of modulated EMS of the hip and shin muscles from 3 to 9 procedures. Preliminary results of the study showed good patient acceptance of EMS. After the course, the EMS group showed a significant improvement from baseline in the Tinetti Test (+1.4 points, p = 0.0045), Rivermead Mobility Index (+0.5 points, p = 0.0022), and Timed Up and Go Test (−1.2 s, p = 0.0053). There was also a significant improvement in balance quality of 8.6% (p = 0.04). Shin muscle strength, although trending positively, did not change significantly. There was also no change in hip and shin muscles’ tone. No significant changes were observed in the control group in the same tests. It can be concluded that stimulation of the hip and shin muscles with Russian (Kotz) currents has a positive effect on the motor system of elderly neurological patients. Significant effects with a course of short duration indicate that this EMS regimen is promising.

Influence of Body Posture and Apnea Severity on the Tone and Elasticity of Upper Airway Muscles in Awake Patients With Obstructive Sleep Apnea: A Cross-Sectional Study

OBJECTIVE

The purpose of this study was to compare the effect of body posture and apnea severity on the tone, stiffness, and elasticity of upper airway muscles in awake patients with obstructive sleep apnea syndrome (OSAS).

METHODS

Eighty adult patients with OSAS from the Sleep Laboratory of the Bitlis State Hospital between April and December 2021 were included in the study. The tone, stiffness, and elasticity of the genioglossus and accessory muscles (sternocleidomastoid, masseter) were measured while the patients were awake, sitting upright, and in supine posture. According to polysomnography results and the Apnea-Hypopnea Index, patients were classified as mild, moderate, or severe OSAS.

RESULTS

There were 56 male (70%) and 24 female (30%) patients (age 45.0 ± 11.0 years). Tone of genioglossus, masseter, and sternocleidomastoid muscles were higher in supine than in sitting posture (all P < .05). There was no difference in elasticity scores of the bilateral genioglossus muscle in sitting and supine posture (P > .05). The elasticity scores of the sternocleidomastoid and masseter muscles were higher in sitting (all P < .05). An interaction effect of postural change and apnea severity was observed on stiffness scores of the genioglossus muscle (P < .05).

CONCLUSION

Results showed that the genioglossus muscle and accessory muscles take on the inspiratory load that develops with postural strain, regardless of the severity of apnea, in awake patients with OSAS. For participants measured in this study, accessory muscles supported respiration by increasing their elasticity.

The rubber hand illusion in microgravity and water immersion

Our body has evolved in terrestrial gravity and altered gravitational conditions may affect the sense of body ownership (SBO). By means of the rubber hand illusion (RHI), we investigated the SBO during water immersion and parabolic flights, where unconventional gravity is experienced. Our results show that unconventional gravity conditions remodulate the relative weights of visual, proprioceptive, and vestibular inputs favoring vision, thus inducing an increased RHI susceptibility.

ANALYSIS OF INDUCED ISOMETRIC FATIGUING CONTRACTIONS IN BICEPS BRACHII MUSCLES USING MYOTONOMETRY AND SURFACE ELECTROMYOGRAPHIC MEASUREMENTS

Viscoelastic properties of skeletal muscle tissue are known to be impacted by fatiguing contractions. In this study, an attempt has been made to utilize myotonometry for analyzing the relationship between muscle viscoelasticity and contractile behaviors in a fatiguing task. For this purpose, thirteen young healthy volunteers are recruited to perform the fatiguing isometric task and the time to task failure (TTF) is recorded. Myotonometric parameters and simultaneous surface electromyographic (sEMG) signals are recorded from the Biceps Brachii muscle of the flexed arm. The correlation between myotonometric parameters and TTF is further analyzed. Cross-validation with sEMG features is also performed. Stiffness of muscle has a positive correlation with TTF in the left hand ([Formula: see text]). Damping property of the nonfatigued muscle is positively associated with the fatigue-induced changes in amplitude features of sEMG signal in the right hand ([Formula: see text]). The normalized rate of change of mean frequency of sEMG signal has a positive correlation with stiffness values in both of the hands ([Formula: see text]). Muscle viscoelasticity is demonstrated to influence the progression of fatigue, although the difference in motor control due to handedness is also found to be an important factor. The results are promising to improve the understanding of the effect of muscle mechanics in fatigue-induced task failure.

Relationship between Viscoelastic Properties of Tissues and Bioimpedance Spectroscopy in Breast-Cancer-Related Lymphedema

The aim of this study was to assess the relationship between the viscoelastic properties of tissues and breast-cancer-related lymphedema (BCRL). After a mastectomy, 46 females were allocated into a lymphedema group (L; n = 15, lymphedema occurred) and a control group (C; n = 31, lack of lymphedema). Bioimpedance spectroscopy was used to test BCRL. The mechanical properties of the tissues in both upper limbs were tested using myotonometry. In group L, tone, stiffness, relaxation time, and creep measured on the biceps brachii of the impaired limb significantly differed from the results on the unimpaired limb. In group C, the differences were not significant. Moreover, both tone and stiffness were inversely correlated with the level of lymphedema (r = −0.72 and r = −0.88, respectively), and both relaxation and creep were significantly related to the level of lymphedema (r = 0.71 and r = 0.59, respectively), when myotonometry was completed on the biceps brachii of the impaired limb in group L. The relationships were not significant in group C. Measurements of viscoelastic properties can provide useful information concerning lymphedema. Our findings suggest that significant correlations between selected mechanical properties of the tissues and BCRL can be used in BCRL detection and treatment.

MyotonPro Is a Valid Device for Assessing Wrist Biomechanical Stiffness in Healthy Young Adults

Background

The MyotonPro is a portable device for measuring biomechanical and viscoelastic properties in superficial soft tissues. The aims of this study are firstly to validate the MyotonPro compared to a reliable gold-standard frame and secondly to observe the influence of MyotonPro measurement on the total wrist viscoelasticity.

Methods

Three silicone polymers with different elastic properties were assessed with the MyotonPro and with a reference rheometer (Universal Tribometer Mod). Then, a free oscillations method was used to measure the passive elastic and viscous stiffness of the wrist and compared to MyotonPro forearm measurements.

Results

A one-way ANOVA demonstrated the validity of the MyotonPro's stiffness (p = 0.001), decrement (p < 0.001), and relaxation (p = 0.008) parameters for measuring the elastic stiffness (k) of the three polymers. The MyotonPro parameters demonstrated excellent reliability on the forearm. Proximal and distal anterior myofascial measurements of the MyotonPro were moderately correlated to the elastic stiffness (p = 0.0027-0.0275, absolute r = from 0.270 to 0.375) of the wrist while the postero-distal myofascial tissues of the forearm demonstrated a moderate correlation with the viscous stiffness of the wrist (p = 0.0096-0.0433, absolute r = from 0.257 to 0.326).

Discussion

The MyotonPro is a valid device for measuring elastic stiffness as well as a portable, affordable, and easy-to-use tool for quantifying the biomechanical properties and viscoelasticity of myofascial tissue in healthy subjects.

Asymmetric Biomechanical Properties of the Paravertebral Muscle in Elderly Patients With Unilateral Chronic Low Back Pain: A Preliminary Study

Background: Clinical incidences of chronic low back pain among the elderly are increasing. However, studies have not fully elucidated on changes in biomechanical properties of paravertebral muscles in patients with unilateral chronic low back pain. We evaluated the changes in biomechanical properties of painful and non-painful paravertebral muscles in elderly patients with unilateral chronic low back pain.

Methods: Biomechanical properties of paravertebral muscles, including muscle tone and stiffness, in elderly patients with unilateral chronic low back pain were measured using MyotonPRO. Lumbar Lordosis and Sacral Slope were measured by magnetic resonance imaging. Cross-sectional areas of paravertebral muscles were evaluated using ImageJ software version 1.53. Chronic low back pain severity was assessed by Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) scores. The correlations between VAS scores, ODI scores, Lumbar Lordosis, Sacral Slope, cross-sectional areas (painful side), disease duration, and biomechanical properties of paravertebral muscles in the painful side were analyzed.

Results: A total of 60 elderly patients with unilateral chronic low back pain were enrolled in this study. The muscle tone and stiffness of paravertebral muscles on the painful side were significantly higher than those on the non-painful side (p &lt; .05). Cross-sectional areas of paravertebral muscles on the painful side at the L3 level were smaller than those of the non-painful side (p &lt; .05). The VAS scores and ODI scores were significantly positively correlated with muscle tone and stiffness of paravertebral muscles on the painful side (p &lt; .05 and p &lt; .01, respectively). There were no significant correlations between disease duration, cross-sectional areas (painful side), Lumbar Lordosis, or Sacral Slope and muscle tone and stiffness of paravertebral muscles on the painful side (p &gt; .05).

Conclusion: In elderly patients with unilateral chronic low back pain, muscle tone and stiffness of paravertebral muscles on the painful side are higher than for those on the non-painful side. The asymmetry of biomechanical properties of paravertebral muscles is associated with severity of chronic low back pain.

Modulation in the Stiffness of Specific Muscles of the Quadriceps in Patients With Knee Osteoarthritis and Their Relationship With Functional Ability

Deficits in the flexibility of the quadriceps are one of the risk factors for developing knee joint disorders. No studies have investigated the changes in the stiffness of the quadriceps muscle among patients with knee osteoarthritis (OA). Therefore, the purpose of this study was to investigate changes in the stiffness of specific-muscle of the quadriceps in patients with knee OA and their relationship with functional ability. Twenty-five patients with knee OA and 25 healthy, asymptomatic subjects were recruited in this study. The stiffness of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) in all participants was evaluated using MyotonPRO at 60° and 90° flexion of the knee joint. The results of this study showed a greater VL stiffness in patients with knee OA than in healthy subjects at both 60° and 90° of knee flexion (p &lt; 0.05). Significant differences in VL, VM and RF stiffness were obtained at different knee joint angles in individuals with and without knee OA (p &lt; 0.05). In addition, there was a positive correlation between VL stiffness and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores in patients with Knee OA (60° of knee flexion: r = 0.508, p = 0.010; 90° of knee flexion: r = 0.456, p = 0.022). These results indicate that there is an increase in VL stiffness in patients with knee OA compared with healthy, asymptomatic subjects, and the quadriceps stiffness was increased with knee flexion in both healthy subjects and patients with knee OA. VL stiffness is associated with WOMAC scores in patients with knee OA.

An Identical Twin Study on Human Achilles Tendon Adaptation: Regular Recreational Exercise at Comparatively Low Intensities Can Increase Tendon Stiffness

Achilles tendon adaptation is a key aspect of exercise performance and injury risk prevention. However, much debate exists about the adaptation of the Achilles tendon in response to exercise activities. Most published research is currently limited to elite athletes and selected exercise activities. Also, existing studies on tendon adaptation do not control for genetic variation. Our explorative cross-sectional study investigated the effects of regular recreational exercise activities on Achilles tendon mechanical properties in 40 identical twin pairs. Using a handheld oscillation device to determine Achilles tendon mechanical properties, we found that the Achilles tendon appears to adapt to regular recreational exercise at comparatively low intensities by increasing its stiffness. Active twins showed a 28% greater Achilles tendon stiffness than their inactive twin (p < 0.05). Further, our research extends existing ideas on sport-specific adaptation by showing that tendon stiffness seemed to respond more to exercise activities that included an aerial phase such as running and jumping. Interestingly, the comparison of twin pairs revealed a high variation of Achilles tendon stiffness (305.4–889.8 N/m), and tendon adaptation was only revealed when we controlled for genetic variance. Those results offer new insights into the impact of genetic variation on individual Achilles tendon stiffness, which should be addressed more closely in future studies.

Assessing the Effects of Aging on Muscle Stiffness Using Shear Wave Elastography and Myotonometer

The current study investigated the differences in muscle stiffness between older and young adults at rest and during contraction. We also evaluated the differences in muscle stiffness assessments using a myotonometer (MyotonPRO) and shear wave elastography (SWE). Twenty-two older adults (mean age, 66.6 ± 1.6 years) and 23 young adults (mean age, 66.6 ± 1.6 years) participated in this study. Muscle stiffness of the tibialis anterior (TA) and medial gastrocnemius (MG) muscles at rest and during contraction were measured using SWE and the MyotonPRO. The stiffness increase rate (SIR) was also calculated to determine the absolute stiffness difference. The mean muscle stiffness of the TA and MG muscles was significantly lower in older adults than in young adults at rest and during contraction (p < 0.05). Similarly, the SIR values of the TA and MG were significantly lower in older adults than in young adults (p < 0.05). Our results indicate that both instruments could be used to quantify muscle stiffness changes and serve as a cornerstone for assessing aging-related losses in muscle function. Stiffness measures may help exercise professionals to develop an in-depth understanding of muscle impairment at the tissue level.

Skin biomechanical and viscoelastic properties measured with MyotonPRO in different areas of human body

BACKGROUND

There is still a lack of clinically practical device, which allows to perform rapid and accurate examination of the skin condition. For this reason, suitability of the MyotonPRO for the assessment of skin biomechanical and viscoelastic parameters was evaluated in this study. The aim of the study was to establish the reference values of five parameters measured by MyotonPRO various locations of human skin.

MATERIALS AND METHODS

Oscillation frequency, dynamic stiffness, logarithmic decrement, mechanical stress relaxation and creep were measured at three different skin locations (clavicula, volar forearm and shin), using L-shape short and medium arm probes in 32 young female volunteers. Mean values of obtained parameters recorded by both probes were compared among three skin locations while reliabilities of measurements were assessed. Additionally, relationships between all recorded parameters were examined RESULTS: There were no statistically significant differences between the mean values of five measured parameters obtained with both probes in all investigated areas. However, statistically significant differences of mean values of almost all parameters measured among three places examined were found. Despite considerable differences in mean values of obtained parameters, there were visible strong correlations between some studied parameters in all three investigated areas of skin.

CONCLUSION

It was demonstrated in all locations studied that the higher value of oscillation frequency corresponds to the higher value of dynamic stiffness, moreover such tissue recovers faster to its initial shape, and it was characterized by lower creep values. Such results indicate the existence of identical relationships between the same studied parameters in different areas of skin.

Immersive Virtual Reality and Vestibular Rehabilitation in Multiple Sclerosis: Case Report

Background

Dizziness and imbalance are common and disabling symptoms in patients with multiple sclerosis (MS) and are caused by a central, peripheral, or mixed vestibulopathy. Central vestibular disorder is the most frequently reported vestibular problem in the MS population due to demyelination. Vestibular rehabilitation ameliorates these symptoms and their repercussions and improves quality of life. Immersive virtual reality (VRi) is an emerging tool in this field; however, no previous research has been performed studying its effects in MS.

Objective

The aim of this study was to apply a VRi vestibular training protocol to a patient with MS and assess the effects induced by the experimental intervention.

Methods

This case study included a 54-year-old woman with relapsing-remitting MS. We developed a standardized VRi exercise protocol for vestibular rehabilitation based on the gold-standard Cawthorne-Cooksey vestibular training protocol. The 20-session intervention was made up of 10 initial sessions and 10 advanced sessions. Each 50-minute session was performed two to three times per week for 7 weeks. Four evaluations were carried out over the study period: at baseline (T0), between initial and advances phases (T1), postintervention (T2), and 1 month after the experimental procedure (T3). The research outcomes were dizziness, balance, gait, impact of fatigue, quality of life, repercussions in muscular tone, and usability of the head-mounted display device.

Results

After implementing the VRi vestibular protocol, improvements were seen in the following patient parameters: Dizziness Handicap Inventory score (62 points at T0; 4 points at T2); Berg Balance Scale score (47 points at T0; 54 points at T2); instrumented Timed Up and Go time (8.35 seconds at T0; 5.57 seconds at T2); muscular tone of the erector spinae, rectus femoris, and soleus; Modified Fatigue Impact Scale score (61 points at T0; 37 points at T2); and Multiple Sclerosis Quality of Life-54 values (67.16% in the physical health area at T2; 33.56% in the mental health area at T2). The patient rated the usability of the system as 90%, based on the System Usability Scale, and gave the system a grade of A.

Conclusions

Although further research is needed, this study provided initial evidence that the first VRi vestibular protocol for the MS population can improve dizziness, balance, gait, impact of fatigue, quality of life, and muscular tone through an exergame intervention. This study may help establish a standardized VRi protocol for vestibular rehabilitation.

Effects of Age and Sex on Properties of Lumbar Erector Spinae in Healthy People: Preliminary Results From a Pilot Study

Background: The influences of age and sex on properties of lumbar erector spinae have not been previously studied. Changes in the performance of lumbar erector spinae properties associated with age represent a valuable indicator of risk for lower-back-related disease.

Objective: To investigate the lumbar erector spinae properties with regard to age and sex to provide a reference dataset.

Methods: We measured muscle tone and stiffness of the lumbar erector spinae (at the L3–4 level) in healthy men and women (50 young people, aged 20–30 years; 50 middle-aged people, aged 40–50 years; and 50 elderly people, aged 65–75 years) using a MyotonPRO device.

Results: In general, there are significant differences in muscle tone and stiffness among young, middle-aged, and elderly participants, and there were significant differences in muscle tone and stiffness between men and women, and there was no interaction between age and sex. The muscle tone and stiffness of the elderly participants were significantly higher than those of the middle-aged and young participants (P < 0.01), and the muscle tone and stiffness of the middle-aged participants were significantly higher than those of the young participants (P < 0.01). In addition, the muscle tone and stiffness of men participants were significantly higher than that of women participants (P < 0.01).

Conclusion: Our results indicate that muscle tone and stiffness of the lumbar erector spinae increase with age. The muscle tone and stiffness of the lumbar erector spinae in men are significantly higher than in women. The present study highlights the importance of considering age and sex differences when assessing muscle characteristics of healthy people or patients.

Effects of Radial Extracorporeal Shock Wave Therapy on Flexor Spasticity of the Upper Limb in Post-stroke Patients: Study Protocol for a Randomized Controlled Trial

Background: Flexor spasticity of the upper limb is common in poststroke patients and seriously affects the recovery of upper limb function. However, there are no standard management protocols for this condition. Radial extracorporeal shock wave therapy (rESWT) is widely used for various diseases, some studies reported the effects of ESWT on reducing spasticity, but the mechanism of ESWT to reduce spasticity by affecting the excitability of stretch reflex or non-neural rheological components in spastic muscles or both is not yet clear. A large randomized controlled trial with comprehensive evaluation indicators is still needed. The study is to observe the effect of rESWT on flexor spasticity of the upper limb after stroke and explore its mechanism.

Methods: A prospective, randomized, double-blind controlled trial is to be performed. One hundred participants will be recruited from the Inpatient Department of Zhujiang Hospital. Eligible patients will be randomly allocated to either receive three sessions of active rESWT (group A) or sham-placebo rESWT (group B) with 3-day intervals between each session. Assessment will be performed at baseline and at 24 h after each rESWT (t1, t2, and t3). The primary assessment outcome will be the Modified Ashworth Scale, and other assessments include surface electromyography, MyotonPRO digital muscle function evaluation, and infrared thermal imaging. All data will be analyzed using intention-to-treat principles. Multiple imputation by chained equations will be used to address missing data caused by loss to follow-up and nonresponses. Per protocol, analyses will also be performed on the participants who complete other assessments. Statistical analysis will be performed using SPSS software (version 20.0) and the significance level set at p < 0.05.

Discussion: This trial aims to analyze the application of rESWT for the management of spasticity after stroke via appropriate assessments. We hypothesized that after receiving active rESWT, patients would show greater improvement of upper limb muscles compared with patients within the sham-placebo group. The rESWT would be an alternative to traditional methods, and the results of this study may provide support for the further study of potential mechanisms.

Clinical Trial Registration:www.chictr.org.cn, identifier: ChiCTR1800016144.

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

PURPOSE

Proper 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.

METHODS

Five 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.

RESULTS

Significant 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).

CONCLUSIONS

Our 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.

Sharp Changes in Muscle Tone in Humans Under Simulated Microgravity

A decrease in muscle tone induced by space flight requires a standardized assessment of changes to control the state of the neuromuscular system. This study is a step toward the development of a unified protocol, aimed at determining the initial effect of the presence or withdrawal of support on muscle tone, the effects of a 2-h supportlessness in Dry Immersion (DI) experiments, and the changes in muscle tone depending on the site of measurement. To perform measurements of changes in muscle tone, we used a MyotonPRO device. The list of muscles that we assessed includes: trunk – mm. deltoideus posterior, trapezius, erector spinae; leg – mm. biceps femoris, rectus femoris, tibialis anterior, soleus, gastrocnemius; foot – m. flexor digitorum brevis, tendo Achillis, aponeurosis plantaris. The study involved 12 healthy volunteers (6 men, 6 women) without musculoskeletal disorders and aged 32.8 ± 1.6 years. At the start of DI, there was a significant decrease in muscle tone of the following muscles: mm. tibialis anterior (−10.9%), soleus (−9.6%), erector spinae (−14.4%), and the tendo Achillis (−15.3%). The decrease continued to intensify over the next 2 h. In contrast, the gastrocnemius muscle demonstrated an increase in muscle tone (+7.5%) 2 h after the start of DI compared to the immediate in-bath baseline. Muscle tone values were found to be site-dependent and varied in different projections of mm. erector spinae and soleus. In previous experiments, we observed a high sensitivity of the myotonometry technique, which was confirmed in this study. To make it possible to compare data from different studies, a standardized protocol for measuring muscle tone for general use in gravitational physiology needs to be developed.

Diurnal variations in the expression of core-clock genes correlate with resting muscle properties and predict fluctuations in exercise performance across the day

Objectives

In this study, we investigated daily fluctuations in molecular (gene expression) and physiological (biomechanical muscle properties) features in human peripheral cells and their correlation with exercise performance.

Methods

21 healthy participants (13 men and 8 women) took part in three test series: for the molecular analysis, 15 participants provided hair, blood or saliva time-course sampling for the rhythmicity analysis of core-clock gene expression via RT-PCR. For the exercise tests, 16 participants conducted strength and endurance exercises at different times of the day (9h, 12h, 15h and 18h). Myotonometry was carried out using a digital palpation device (MyotonPRO), five muscles were measured in 11 participants. A computational analysis was performed to relate core-clock gene expression, resting muscle tone and exercise performance.

Results

Core-clock genes show daily fluctuations in expression in all biological samples tested for all participants. Exercise performance peaks in the late afternoon (15–18 hours for both men and women) and shows variations in performance, depending on the type of exercise (eg, strength vs endurance). Muscle tone varies across the day and higher muscle tone correlates with better performance. Molecular daily profiles correlate with daily variation in exercise performance.

Conclusion

Training programmes can profit from these findings to increase efficiency and fine-tune timing of training sessions based on the individual molecular data. Our results can benefit both professional athletes, where a fraction of seconds may allow for a gold medal, and rehabilitation in clinical settings to increase therapy efficacy and reduce recovery times.

Validity and reliability of myotonometry for assessing muscle viscoelastic properties in patients with stroke: a systematic review and meta-analysis

There is a lack of consensus about the measurement of the muscle viscoelastic features in stroke patients. Additionally, the psychometric properties of the most-commonly used clinical tools remain controversial. Our objective is to investigate the validity and reliability of myotonometry to assess viscoelastic muscle features in stroke survivors. Pubmed, PEDro, Scopus and Cinahl were systematically searched to include studies reporting the psychometric properties of myotonometric devices used in people after stroke. The QUADAS-2 and the COSMIN checklists were used to assess the methodological quality of the studies and the psychometric properties of myotonometry. Nine studies were included in the qualitative synthesis and data from five of these were pooled in a meta-analysis. Overall, low to moderate risk of bias and applicability concerns were observed. Pooled data from intra-rater reliability for muscle tone showed a mean coefficient of correlation of 0.915 (95% CI: 0.880-0.940, I 2 = 69.2%) for upper limbs, and a mean coefficient of 0.785 (95%CI: 0.708-0.844, I 2 = 4.02%) for lower limbs. Myotonometry seems to be a valid and reliable complementary tool to assess muscle viscoelastic properties in stroke survivors, although definite conclusions about concurrent validity need further research.

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.

Stiffness of the Gastrocnemius-Achilles Tendon Complex Between Amateur Basketball Players and the Non-athletic General Population

Muscle and tendon stiffness are related to sports performance, tendinopathy, and tendon degeneration. However, the effects of habitual loading on muscle and tendon mechanical properties are unclear. Using amateur basketball players as examples, we investigated the effects of mechanical loading on the stiffness of the gastrocnemius–Achilles tendon (AT) complex in non-dominant and dominant lower limbs. Then, we evaluated the correlation between gastrocnemius and AT stiffness. Forty participants (20 amateur basketball players; 20 normal non-athletic persons) were recruited for this study. Stiffness of the gastrocnemius–AT complex was assessed using MyotonPRO at neutral position and 10° dorsiflexion of the ankle joint in participants from amateur basketball players and the non-athletic general population. Our results showed a greater stiffness of the gastrocnemius–AT complex in amateur basketball players than that in healthy non-athletic subjects at neutral position and 10° dorsiflexion of the ankle joint (P < 0.05). No significant difference in stiffness was found between the non-dominant and dominant lower limbs either in amateur basketball players or in generally healthy subjects (P > 0.05). A significant positive correlation was obtained between stiffness of the AT and medial gastrocnemius (MG) in amateur basketball players (neutral position: r = 0.726 and P = 0.001; dorsiflexion 10°: r = 0.687 and P = 0.001). The amateur basketball players exhibit significantly higher stiffness value in Achilles and gastrocnemius. This is possibly caused by repeated training effects. The symmetric stiffness of the AT and gastrocnemius exists both in amateur basketball players and generally healthy subjects. A significant correlation between the AT and the MG was found in amateur basketball players.

Effect of a Long Exercise Program in the Reduction of Musculoskeletal Discomfort in Office Workers

The purpose of this study was to assess the effect of a six week exercise program to reduce the muscle tone of the trapezius and musculoskeletal discomfort (MED) of office workers. Twenty-six workers performed an exercise program based on: (1) stretching of cervical and/or dorsal region; (2) joint mobility of shoulders and rachis; (3) strengthening deep stabilizer and core muscles; and (4) scapula stabilizing exercises. A Myoton device was used to evaluate trapezius tone and the Cornell Musculoskeletal Discomfort Questionnaire was used to assess changes in MED at three points of evaluation: at the beginning (Pre_1) and at the end of the workday (Post_1), and after the training program (Pre_2). The Wilcoxon test and Cohen’s d were performed to examine differences and effect sizes between evaluations. Main results show that trapezius tone remained constant during the workday, but decreased in the dominant upper trapezius (p = 0.003, ES = −0.60) and increased in the non-dominant middle trapezius (p = 0.016, ES = 0.45) after the exercise program, which eliminated significant muscle asymmetries. MED significantly decreased in the neck (p = 0.027, ES = −0.60) and upper back (p = 0.046, ES = −0.67). In conclusion, MED appears to improve in office workers after a six week training program, which may be explained by a decrease in trapezius tone and increase in the left middle trapezius tone.

Phantom material testing indicates that the mechanical properties, geometrical dimensions, and tensional state of tendons affect oscillation-based measurements

OBJECTIVE

There is an increasing interest in the application of oscillation-based measurement techniques to evaluate the mechanical stiffness of healthy and diseased tendons. These techniques measure the stiffness of a tendon indirectly by registering the oscillation response of a tendon to an external mechanical impulse. Although these measurement techniques seem to be comparatively easy and time-saving, their applicability is implicitly limited by their indirect measurement principle.

APPROACH

In this study, we aim to find evidence that the oscillation response of a tendon to an external mechanical impulse is not only affected by the stiffness of a tendon but also by the tendons' cross-sectional area (CSA), length, and tension. Therefore, we reviewed the current literature on oscillation-based techniques that measure in vivo tendon properties. Further, a phantom material was used to mimic the nature of tendons and to test the impact of four factors on oscillation-based measurements.

MAIN RESULTS

Our results indicate that the mechanical properties, geometrical dimensions (length and CSA), and tensional state affect oscillation-based measures. Surprisingly, most studies on tendon behavior often exclusively associate their oscillation-based measurements with the mechanical stiffness of a tendon.

SIGNIFICANCE

While this narrow perspective bears the risk of misinterpretation or false implications, a broader understanding of oscillation-based measurements has the potential to shed new light on the interaction of muscles and tendons in vivo.

Eccentric Exercise Reduces Upper Trapezius Muscle Stiffness Assessed by Shear Wave Elastography and Myotonometry

In this study, we tested the hypotheses that unaccustomed eccentric exercise (ECC) would reduce the elastic modulus and dynamic stiffness of the upper trapezius muscle and that these changes would correlate with increases in muscle thickness, reflecting muscle edema. Shear wave elastography was used to measure elastic modulus, dynamic stiffness was assessed using myotonometry, and muscle thickness was measured using ultrasonography. All measurements were performed at four locations over the upper trapezius before and 24 h after a single bout of ECC. Fourteen healthy participants (11 males and 3 females; 23.2 ± 3.0 years; height 175.1 ± 10.4 cm; body mass 73.8 ± 11.3 kg) took part in the study. Overall, ECC resulted in decreased elastic modulus (from 45.8 ± 1.6 to 39.4 ± 1.2 kPa, p < 0.01) and dynamic muscle stiffness (from 369.0 ± 7.3 to 302.6 ± 6.0 N/m, p < 0.01). Additionally, ECC resulted in increased muscle thickness (from 6.9 ± 0.4 to 7.3 ± 0.4 mm, p < 0.01). Spatial changes (across the four locations) were found for elastic modulus, stiffness and thickness. No significant correlations were found between changes in measures of muscle stiffness, or between changes in stiffness and changes in thickness. In conclusion, the present pilot study showed that ECC altered biomechanical muscle properties, reflected by decreased elastic modulus and dynamic muscle stiffness 24 h after ECC.

Influence of different knee and ankle ranges of motion on the elasticity of triceps surae muscles, Achilles tendon, and plantar fascia

Stiffness is a valuable indicator of the functional capabilities of muscle-tendon-fascia. Twenty healthy subjects participated in this study in which the passive elastic properties of the medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus muscles (SOL), Achilles tendon (AT, at 0 cm, 3 cm and 6 cm proximal to the calcaneus tubercle, corresponding to AT0cm, AT3cm and AT6cm, respectively) and plantar fascia (PF) were quantified when their knee was fully extended or flexed to 90° using shear wave elastography at 25° of dorsiflexion (DF25°), 0° (neutral position) of flexion, and 50° of plantar flexion (PF50°) of the ankle joint. The stiffnesses of the AT, MG, LG, SOL and the fascia with the knee fully extended were significantly higher than those with the knee flexed to 90° (p < 0.05), while the stiffness of the PF showed the opposite relationship (p < 0.05). When the knee was fully extended, the stiffness was higher in the LG than in the MG at PF50° and 0° (p < 0.01), and it was higher in the MG than in the LG at DF25° (p = 0.009). Nevertheless, regardless of the knee angle, the stiffness decreased from AT3cm > AT0cm > AT6cm at PF50° and 0° (p < 0.001), while the stiffness decreased from AT0cm > AT3cm > AT6cm at DF25°. Regardless of the knee and ankle angles, the stiffness of the PF increased in a proximal-to-distal direction (p < 0.001). These insights can be used to gain a more intuitive understanding of the relationships between the elastic properties of the muscle-tendon unit and its function.

Influence of different knee and ankle ranges of motion on the elasticity of triceps surae muscles, Achilles tendon, and plantar fascia

Stiffness is a valuable indicator of the functional capabilities of muscle-tendon-fascia. Twenty healthy subjects participated in this study in which the passive elastic properties of the medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus muscles (SOL), Achilles tendon (AT, at 0 cm, 3 cm and 6 cm proximal to the calcaneus tubercle, corresponding to AT0cm, AT3cm and AT6cm, respectively) and plantar fascia (PF) were quantified when their knee was fully extended or flexed to 90° using shear wave elastography at 25° of dorsiflexion (DF25°), 0° (neutral position) of flexion, and 50° of plantar flexion (PF50°) of the ankle joint. The stiffnesses of the AT, MG, LG, SOL and the fascia with the knee fully extended were significantly higher than those with the knee flexed to 90° (p < 0.05), while the stiffness of the PF showed the opposite relationship (p < 0.05). When the knee was fully extended, the stiffness was higher in the LG than in the MG at PF50° and 0° (p < 0.01), and it was higher in the MG than in the LG at DF25° (p = 0.009). Nevertheless, regardless of the knee angle, the stiffness decreased from AT3cm > AT0cm > AT6cm at PF50° and 0° (p < 0.001), while the stiffness decreased from AT0cm > AT3cm > AT6cm at DF25°. Regardless of the knee and ankle angles, the stiffness of the PF increased in a proximal-to-distal direction (p < 0.001). These insights can be used to gain a more intuitive understanding of the relationships between the elastic properties of the muscle-tendon unit and its function.

Influence of different knee and ankle ranges of motion on the elasticity of triceps surae muscles, Achilles tendon, and plantar fascia

Stiffness is a valuable indicator of the functional capabilities of muscle-tendon-fascia. Twenty healthy subjects participated in this study in which the passive elastic properties of the medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus muscles (SOL), Achilles tendon (AT, at 0 cm, 3 cm and 6 cm proximal to the calcaneus tubercle, corresponding to AT0cm, AT3cm and AT6cm, respectively) and plantar fascia (PF) were quantified when their knee was fully extended or flexed to 90° using shear wave elastography at 25° of dorsiflexion (DF25°), 0° (neutral position) of flexion, and 50° of plantar flexion (PF50°) of the ankle joint. The stiffnesses of the AT, MG, LG, SOL and the fascia with the knee fully extended were significantly higher than those with the knee flexed to 90° (p < 0.05), while the stiffness of the PF showed the opposite relationship (p < 0.05). When the knee was fully extended, the stiffness was higher in the LG than in the MG at PF50° and 0° (p < 0.01), and it was higher in the MG than in the LG at DF25° (p = 0.009). Nevertheless, regardless of the knee angle, the stiffness decreased from AT3cm > AT0cm > AT6cm at PF50° and 0° (p < 0.001), while the stiffness decreased from AT0cm > AT3cm > AT6cm at DF25°. Regardless of the knee and ankle angles, the stiffness of the PF increased in a proximal-to-distal direction (p < 0.001). These insights can be used to gain a more intuitive understanding of the relationships between the elastic properties of the muscle-tendon unit and its function.