Local alternating heat and cold stimulation affects hemodynamics and oxygenation in fatigued muscle tissue and autonomic nervous activity: a single-arm interventional study.

BACKGROUND: Local alternating heat and cold stimulation as an alternative to contrast bath may cause intermittent vasoconstriction and vasodilation, inducing a vascular pumping effect and consequently promoting increased tissue blood flow and oxygenation. This study aimed to examine the effects of local alternating heat and cold stimulation, using a wearable thermal device, on the hemodynamics of fatigued muscle tissue and autonomic nervous activity. METHODS: Twenty healthy individuals experienced fatigue in the periarticular muscles of the shoulder joint due to a typing task. Local alternating heat and cold stimulations were then applied to the upper trapezius muscle. Muscle hardness was measured using a muscle hardness meter, and muscle tissue hemodynamics and oxygenation were evaluated using near-infrared spectroscopy before and after the stimulation. Autonomic nervous activity was also evaluated using heart rate variability. RESULTS: Alternating heat and cold stimulation decreased muscle hardness of the fatigued trapezius muscle from 1.38 ± 0.15 to 1.31 ± 0.14 N (P < 0.01). The concentration of total hemoglobin in the trapezius muscle tissue increased from - 0.21 ± 1.36 to 2.29 ± 3.42 µmol/l (P < 0.01), and the tissue hemoglobin oxygen saturation also increased from 70.1 ± 5.4 to 71.1 ± 6.0% (P < 0.05). Additionally, the heart rate variability parameter, which is an index of sympathetic nervous activity, increased from 3.82 ± 2.96 to 6.86 ± 3.49 (P < 0.01). A correlation was found between increased tissue hemoglobin oxygen saturation and increased parameters of sympathetic nervous activity (r = 0.50, P < 0.05). CONCLUSIONS: Local alternating heat and cold stimulation affected the hemodynamic response in fatigued muscle tissue and autonomic nervous activity. This stimulation is more efficient than conventional contrast baths in terms of mobility and temperature control and has potential as a new versatile therapeutic intervention for muscle fatigue. TRIAL REGISTRATION: UMIN-CTR (UMIN000040087: registered on April 7, 2020, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000045710 . UMIN000040620: registered on June 1, 2020, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000046359 ).

Cluster Analysis of Subjective Shoulder Stiffness and Muscle Hardness: Associations with Central Sensitization-Related Symptoms.

Background and Objectives: Understanding the relationships between subjective shoulder stiffness, muscle hardness, and various factors is crucial. Our cross-sectional study identified subgroups of shoulder stiffness based on symptoms and muscle hardness and investigated associated factors. Materials and Methods: measures included subjective stiffness, pain, muscle hardness, and factors like physical and psychological conditions, pressure pain threshold, postural alignment, heart rate variability, and electroencephalography in 40 healthy young individuals. Results: Three clusters were identified: Cluster 1 with high stiffness, pain, and muscle hardness; Cluster 2 with low stiffness and pain but high muscle hardness; and Cluster 3 with low levels of all factors. Cluster 1 had significantly higher central sensitization-related symptoms (CSS) scores than Cluster 2. Subjective stiffness is positively correlated with psychological factors. Conclusions: our results suggest that CSS impacts subjective symptom severity among individuals with similar shoulder muscle hardness.

Dietary threonine improves muscle nutritional value and muscle hardness associated with collagen synthesis in grass carp (Ctenopharyngodon idella).

To further explain the improvement effect of threonine (Thr) on the fillet quality of fish, a 9-week feeding experiment was conducted. After feeding graded levels of Thr (2.38, 5.38, 8.38, 11.38, 14.38 and 17.38 g/kg), the compositions of fillet hydrolyzed amino acid and fatty acid, and the muscle hardness associated with collagen biosynthesis were mainly analyzed in grass carp (Ctenopharyngodon idella). The results showed that Thr increased the pH value, changed the amino acids and fatty acid composition of fillets, especially essential amino acid (EAA), C22:6n3 (DHA) and C20:5n3 (EPA). Furthermore, this study revealed for the first time that the improvement of muscle hardness by Thr was associated with collagen biosynthesis, and the TGF-ß1/Smads, LARP6a and Hsp47 regulate transcriptional processes, translation initiation and post-translational modifications in collagen biosynthesis, respectively. This study offered a basis for exploring the contribution of Thr in improving muscle quality in sub-adult grass carp.

Comparative Study of Muscle Hardness during Water-Walking and Land-Walking Using Ultrasound Real-Time Tissue Elastography in Healthy Young People.

Compared with land-walking, water-walking is considered to be beneficial as a whole-body exercise because of the characteristics of water (buoyancy, viscosity, hydrostatic pressure, and water temperature). However, there are few reports on the effects of exercise in water on muscles, and there is no standard qualitative assessment method for muscle flexibility. Therefore, we used ultrasound real-time tissue elastography (RTE) to compare muscle hardness after water-walking and land-walking. Participants were 15 healthy young adult males (24.8 ± 2.3 years). The method consisted of land-walking and water-walking for 20 min on separate days. The strain ratio of the rectus femoris (RF) and medial head of gastrocnemius (MHGM) muscles were measured before and immediately after walking using RTE to evaluate muscle hardness. In water-walking, the strain ratio significantly decreased immediately after water-walking, with p < 0.01 for RF and p < 0.05 for MHGM, indicating a significant decrease in muscle hardness after water-walking. On the other hand, land-walking did not produce significant differences in RF and MHGM. Muscle hardness after aerobic exercise, as assessed by RTE, was not changed by land walking but was significantly decreased by water walking. The decrease in muscle hardness induced by water-walking was thought to be caused by the edema reduction effect produced by buoyancy and hydrostatic pressure.

Muscle damage induced by maximal eccentric exercise of the elbow flexors after 3-week immobilization.

The present study investigated the effects of a 3-week immobilization (IM) on muscle damage induced by maximal eccentric exercise (MaxEC) to test the hypothesis that the IM would make muscles prone to muscle damage. Young healthy sedentary men were pseudo-randomly assigned to IM or control group (n = 12/group). Non-dominant arms of the IM group participants were immobilized at 90° elbow flexion by a cast for 21 days. All participants performed MaxEC consisting of five sets of six elbow flexor contractions by lowering a dumbbell set at 100% of pre-exercise maximal voluntary isometric contraction (MVC) strength of the non-dominant arm. This was performed at 2 days after the cast removal for the IM group. MVC torque, range of motion (ROM), muscle thickness (MT), muscle hardness, position sense (PS), and joint reaction angle (JRA) of the elbow flexors were measured at baseline, post-immobilization, and before, immediately after, and one to 5 days after MaxEC. The IM decreased MVC torque (-17 ± 2%), ROM (-2 ± 1%), MT (-7 ± 3%), and JRA (-12 ± 6%), and increased in muscle hardness (20 ± 6%) and PS (11 ± 2%) (p < 0.05). Changes in MVC (e.g., 2 days: -40 ± 5 vs. -30 ± 9%), ROM (2 days: -11 ± 2 vs. -9 ± 3%), muscle soreness (peak: 63 ± 22 vs. 48 ± 14 mm), plasma CK activity (peak: 7820 ± 4011 vs. 4980 ± 1363 IU/L), PS (maximal change: -23 ± 2 vs. -18 ± 3%), and JRA (maximal change: -37 ± 4 vs. -26 ± 3%) after MaxEC were greater (p < 0.05) for the IM than control group. These results supported the hypothesis and showed that the IM made the muscles more vulnerable to muscle damage induced by eccentric exercise.

Difference of cervical and shoulder muscle performance and its correlation with pain and body mass index in patients with chronic neck pain / 中国康复理论与实践

ObjectiveTo test the inter-tester reliability and test-retest reliability of MyotonPRO for evaluating neck and shoulder muscle performance parameters in patients with unilateral chronic neck pain, observe the difference of muscle performance between the healthy and affected sides of patients with chronic neck pain, and analyze the factors that cause the imbalance of muscle performance in patients with chronic neck pain. MethodsFrom January to June, 2023, 32 patients with unilateral chronic neck pain in Guangdong Second Traditional Chinese Medicine Hospital were selected. Two testers used the same MyotonPRO equipment to measure the muscle tone, muscle hardness and muscle elasticity on both sides of the sternocleidomastoid muscle and the upper trapezius muscle in the relaxed position. Tester 1 repeated the measurement after an interval of 30 minutes, and Tester 2 was measured within the time interval between the two measurements of Tester 1. The intraclass correlation coefficient (ICC), standard error of mean (SEM) and minimum detectable change (MDC) were calculated simultaneously. The measurement results were plotted into Bland-Altman diagram and systematic bias analysis was performed. The difference in muscle characteristics between the affected side and the healthy side was compared. At the same time, the Visual Analogue Scale (VAS) score and body mass index (BMI) of the subjects were collected for correlation analysis. ResultsExcept the sternocleidomastoid muscle elasticity of the affected side (ICC = 0.697), the inter-tester reliability of all other parameters was high to very high (ICC = 0.719 to 0.952, SEM = 0.04 to 6.53, MDC = 0.12 to 18.11). The test-retest reliability of all parameters was high (ICC = 0.883 to 0.981, SEM = 0.03 to 5.72, MDC = 0.09 to 15.84). Bland-Altman plot analysis showed that the scatter distribution was consistent. The muscle tone, muscle hardness and muscle elasticity of sternocleidomastoid muscle and upper trapezius muscle were higher on the affected side than on the healthy side (t > 2.846, P < 0.05). The asymmetry index of tension, hardness and elasticity of upper trapezius muscle and sternocleidomastoid muscle was significantly positively correlated with VAS score and BMI (r > 0.385, P < 0.05). ConclusionMyotonPRO has good inter-tester reliability and retest reliability in evaluating the muscle performance of both sides of patients with chronic neck pain. The muscle tone, muscle hardness and muscle elasticity of sternocleidomastoid muscle and upper trapezius muscle on the affected side were higher than on the healthy side, and the difference of muscle performance was positively correlated with pain and BMI.

Characteristics of paravertebral muscles in patients with unilateral lumbar disc herniation / 中国康复理论与实践

ObjectiveTo explore the imbalance of paravertebral muscle group for patients with unilateral lumbar disc herniation. MethodsFrom January, 2022 to January, 2023, 30 patients with unilateral lumbar disc herniation (observation group) and 30 healthy people matching in general data (control group) were measured the tension and stiffness of multifidus and erector spinae with MyotonPRO, while the observation group was assessed with Visual Analogue Scale (VAS) for pain and Japanese Orthopaedic Association (JOA) score, and the time of disease was also recorded. ResultsThe mean of bilateral tension and hardness of multifidus and erector spinae was more in the observation group than in the control group (|t| > 5.407, P < 0.001), and the tension and hardness of multifidus and erector spinae of the affected side were more than those of the unaffected side in the observation group (|t| > 11.219, P < 0.001). The tension and hardness of multifidus and erector spinae of the affected side were positively correlated with VAS score (r > 0.942, P < 0.001), and negatively correlated with JOA score (|r| > 0.886, P < 0.001). ConclusionThe tension and hardness of multifidus and erector spinae of the affected side increase after unilateral lumbar disc herniation, resulting in asymmetry.

Effects of different intermittent pneumatic compression stimuli on ankle dorsiflexion range of motion.

Despite substantial evidence of the effectiveness of intermittent pneumatic compression (IPC) treatments for range of motion (ROM) improvement, little evidence is available regarding how different IPC stimuli affect ankle dorsiflexion (DF) ROM. This study aimed to investigate the effects of different IPC stimuli on the ankle DF ROM. Fourteen, university intermittent team sport male athletes (age: 21 ± 1 year, height: 1.74 ± 0.05 m, body mass: 70.9 ± 7.7 kg, body fat percentage: 14.2 ± 3.6%, body mass index: 23.5 ± 2.5 kg/m2; mean ± standard deviation) completed four experimental trials in a random order: 1) no compression with wearing IPC devices (SHAM), 2) the sequential compression at approximately 80 mmHg (SQUEE80), 3) the uniform compression at approximately 80 mmHg (BOOST80), and 4) the uniform compression at approximately 135 mmHg (BOOST135). For the experimental trials, the participants were initially at rest for 10 min and then assigned to either a 30-min SHAM, SQUEE80, BOOST80, or BOOST135. Participants rested for 20 min after IPC treatment. The Weight-Bearing Lunge Test (WBLT), popliteal artery blood flow, pressure-to-pain threshold (PPT), muscle hardness, heart rate variability, and perceived relaxation were measured before (Pre) and immediately after IPC treatment (Post-0) and 20 min after IPC treatment (Post-20), and the changes in all variables from Pre (Δ) were calculated. ΔWBLT performance, ΔPPT, and Δperceived relaxation in all IPC treatments were significantly higher than those in SHAM at Post-0 and Post-20 (p < 0.05). ΔPopliteal artery blood flow in BOOST80 and BOOST135 was significantly higher than that in SHAM and SQUEE80 at Post-0 (p < 0.05). ΔMuscle hardness and Δheart rate variability did not differ significantly between trials. In conclusion, IPC treatments, irrespective of applied pressure and mode of compression, increased ankle DF ROM. This resulted from decreased pain sensitivity (i.e., increased PPT). In addition, high inflation pressure and frequency did not provide additional benefits in increasing ankle DF ROM.

Dietary protein levels changed the hardness of muscle by acting on muscle fiber growth and the metabolism of collagen in sub-adult grass carp (Ctenopharyngodon idella).

BACKGROUND: Nutrient regulation has been proven to be an effective way to improve the flesh quality in fish. As a necessary nutrient for fish growth, protein accounts for the highest proportion in the fish diet and is expensive. Although our team found that the effect of protein on the muscle hardness of grass carp was probably related to an increased collagen content, the mechanism for this effect has not been deeply explored. Moreover, few studies have explored the protein requirements of sub-adult grass crap (Ctenopharyngodon idella). Therefore, the effects of different dietary protein levels on the growth performance, nutritional value, muscle hardness, muscle fiber growth, collagen metabolism and related molecule expression in grass carp were investigated. METHODS: A total of 450 healthy grass carp (721.16 ± 1.98 g) were selected and assigned randomly to six experimental groups with three replicates each (n = 25/replicate), and were fed six diets with 15.91%, 19.39%, 22.10%, 25.59%, 28.53% and 31.42% protein for 60 d. RESULTS: Appropriate levels of dietary protein increased the feed intake, percentage weight gain, specific growth rate, body composition, unsaturated fatty acid content in muscle, partial free amino acid content in muscle, and muscle hardness of grass carp. These protein levels also increased the muscle fiber density, the frequency of new muscle fibers, the contents of collagen and IGF-1, and the enzyme activities of prolyl 4-hydroxylases and lysyloxidase, and decreased the activity of matrix metalloproteinase-2. At the molecular level, the optimal dietary protein increased collagen type I α1 (Colα1), Colα2, PI3K, Akt, S6K1, La ribonucleoprotein domain family member 6a (LARP6a), TGF-ß1, Smad2, Smad4, Smad3, tissue inhibitor of metalloproteinase-2, MyoD, Myf5, MyoG and MyHC relative mRNA levels. The levels of the myostatin-1 and myostatin-2 genes were downregulated, and the protein expression levels of p-Smad2, Smad2, Smad4, p-Akt, Akt, LARP6 and Smad3 were increased. CONCLUSIONS: The appropriate levels of dietary protein promoted the growth of sub-adult grass carp and improved muscle hardness by promoting the growth of muscle fibers, improving collagen synthesis and depressing collagen degradation. In addition, the dietary protein requirements of sub-adult grass carp were 26.21% and 24.85% according to the quadratic regression analysis of growth performance (SGR) and the muscle hardness (collagen content), respectively.

Effects of alternating heat and cold stimulation at different cooling rates using a wearable thermo device on shoulder muscle stiffness: a cross-over study.

BACKGROUND: A small, wearable thermo device that uses Peltier elements for programmed heat and cold stimulation has been developed recently and is expected to be applied in conventional contrast bath therapy. This study was aimed to examine improvements in trapezius muscle hardness and subjective symptoms resulting from alternating heat and cold stimulation, with different rates of cooling. METHODS: This cross-over study included four conditions. Twenty healthy young male individuals (age, 22.3 ± 4.5 years) participated in this study. These four interventions targeted the unilateral trapezius muscle of the dominant arm after a 15-min typing task. Specifically, heat and cold stimulations were applied at different ratios (the heating/cooling rate of 3:1, 3:2, and 3:3) or not applied. Each intervention was separated by at least one week. Skin temperature at the stimulation area was recorded using a data logger. Outcome measures included muscle hardness (measured using a portable tester) and subjective symptoms (muscle stiffness and fatigue). Each item was assessed at three time points: baseline, after typing, and after the intervention. RESULTS: Two-way analysis of variance with repeated measures found an interaction effect for muscle hardness between four conditions (3:1, 3:2, 3:3, and no) and three time points (p < 0.05). Only in the 3:1 condition were the post-intervention values lower than those after typing (p < 0.01). There was also an interaction effect for subjective muscle stiffness (p < 0.05); the values after the intervention in the 3:1 condition were lower than those after intervention in the no stimulation condition (p < 0.01). There was no significant relationship between changes in muscle hardness and changes in subjective symptoms in the 3:1 condition. CONCLUSIONS: Our results demonstrate that alternating heat and cold stimulations with a different cooling rate could affect the degree of improvement in muscle hardness and subjective symptoms. In particular, the 3:1 condition has the possibility to improved muscle hardness within the condition and subjective muscle stiffness between conditions. TRIAL REGISTRATION: UMIN000040620. Registered 1 June 2020, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000046359.

Investigation of absolute intra-rater and inter-rater reliabilities during the muscle hardness estimation.

[Purpose] This study aimed to investigate the absolute intra-rater and inter-rater reliabilities during the measurement of muscle hardness, which is used to evaluate physical therapy. Moreover, we examined the effects of using different equipment types and their positioning on the intra-rater and inter-rater reliabilities. [Participants and Methods] Participants of this study comprised 12 healthy adult male individuals. Two experts and two beginners measured the muscle hardness of the lumbar erector spinae and rectus femoris using three types of hardness meters at two positions, including when the muscle was relaxed and stretched. [Results] Intra-rater fixed bias was observed during some measurements by both experts and beginners. Inter-rater fixed bias was observed during measurements by some experts and not the beginners. [Conclusion] In this study, the measurement of muscle hardness demonstrated a need to reconsider the measurement position and acclimation time. These examinations require the consideration of relative and absolute reliabilities.

Effects of alternating heat and cold stimulation using a wearable thermo-device on subjective and objective shoulder stiffness.

BACKGROUND: Technological innovations have allowed the use of miniature apparatus that can easily control and program heat and cold stimulations using Peltier elements. The wearable thermo-device has a potential to be applied to conventional contrast bath therapy. This study aimed to examine the effects of alternating heat and cold stimulation (HC) using a wearable thermo-device on subjective and objective improvement of shoulder stiffness. METHODS: Twenty healthy young male individuals (20.3 ± 0.6 years) participated in this study. The interventions were randomly conducted under four conditions, including HC, heat stimulation, cold stimulation, and no stimulation on their bilateral trapezius muscle, after a 30-min typing task. Each intervention was administered at least 1 week apart. The analyzed limb was the dominant arm. Muscle hardness was assessed using a portable muscle hardness meter, as well as the skin temperature over the stimulated area. After each condition, the participants were asked for feedback regarding subjective improvement in refreshed feelings, muscle stiffness, and muscle fatigue using an 11-point numerical rating scale. RESULTS: With regard to muscle hardness, only the HC condition significantly decreased from 1.43 N to 1.37 N (d = 0.44, p < 0.05). Additionally, reduced muscle hardness in HC condition was associated with the degree of skin cooling during the intervention (cold max: r = 0.634, p < 0.01; cold change: r = -0.548, p < 0.05). Subjective improvement in refreshed feelings, muscle stiffness, and muscle fatigue was determined in the HC and heat stimulation conditions compared with the no stimulation condition (p < 0.01 and p < 0.05, respectively). Moreover, the HC condition showed significantly greater improvements in muscle stiffness and fatigue compared to the cold stimulation condition (p < 0.05). CONCLUSIONS: The current study demonstrated that HC promoted not only better subjective symptoms, such as muscle stiffness and fatigue, but also lesser muscle hardness. Furthermore, an association was observed between the degree of skin temperature cooling and reduced muscle hardness during HC. Further investigations on the ratio and intensity of cooling should be conducted in the future to establish the optimal HC protocol for muscle stiffness or fatigue. TRIAL REGISTRATION: UMIN000040620 . Registered 1 June 2020.

The immediate effects of neuromuscular joint facilitation on chronic low back pain in young and elderly people.

[Purpose] This study aimed to investigate the changes in the pain severity and muscle hardness of the multifidus and longissimus muscles of young and elderly patients with low back pain after neuromuscular joint facilitation treatment. [Participants and Methods] The participants were 13 young patients and 11 elderly patients with chronic low back pain. The neuromuscular joint facilitation lumbar approach was used in all participants. The muscle hardness of the multifidus and longissimus muscles was assessed at the L4 and L5 levels of the lumbar spine. The changes in pain severity of low back pain were assessed using a visual analogue scale before and after treatment. [Results] Visual analogue scale scores significantly decreased in both groups after treatment. The young group showed significant differences in muscle hardness pre- and post-intervention. In addition, except for the muscle hardness of the multifidus muscle before intervention, on the side with pain at the L5 level, longissimus muscle hardness was higher in the elderly, as compared to the young patient group. [Conclusion] Interventions with neuromuscular joint facilitation have an immediate effect on pain relief in young and elderly people with chronic low back pain and on muscle spasms in young people with chronic low back pain.

The effect of foam rollers of varying densities on range of motion recovery.

OBJECTIVE: This study aimed to compare the effect of different density foam rollers on range of motion recovery. METHOD: Ten active men completed two, 3-day trials in random order. During the experimental trials, all participants performed 2 min of foam rolling (FR) using a medium-density (medium trial) or hard-density (hard trial) foam roller on the right posterior thigh after completing the 90-min Loughborough Intermittent Shuttle Test (LIST). The hip joint range of motion (ROM), muscle hardness, and muscle soreness were assessed before and after the LIST and at 0 min, 20 min, 60 min, 24 h, and 48 h after FR intervention. Serum creatine kinase (CK) concentrations were assessed before the LIST and at 60 min, 24 h, and 48 h after FR intervention. The contralateral leg in each trial was used as a control. RESULTS: The ROM at 0 min, 20 min, 60 min, 24 h, and 48 h after FR intervention were higher in the right leg (the massage leg) than in the left leg (the contralateral leg) (p < 0.05). In the right leg, the ROM at 0 min after FR intervention was higher than after the LIST (p < 0.05). There were no significant differences between the medium and hard trials for ROM. Muscle hardness, muscle soreness, and serum CK concentration were not affected by FR. CONCLUSION: FR has a positive effect on ROM recovery. Moreover, the two roller densities provided similar ROM recovery.

Contribution of Plantar Fascia and Intrinsic Foot Muscles in a Single-Leg Drop Landing and Repetitive Rebound Jumps: An Ultrasound-Based Study.

The plantar fascia and intrinsic foot muscles (IFM) modulate foot stiffness. However, it is unclear whether the corresponding ultrasonography findings reflect it. This study aimed to examine the effect of the plantar fascia and IFM morphologies on force attenuation during landing and reactivity when jumping in healthy adults (n = 21; age, 21-27 years). Thickness, cross-sectional area (CSA), and hardness of the plantar fascia, abductor hallucis (AbH), and flexor hallucis brevis (FHB) muscles were measured using ultrasonography. Single-leg drop landing and repetitive rebound jumping tests assessed the ground reaction force (GRF) and reactive jump index (RJI), respectively. The CSA of FHB was negatively correlated with maximum vertical GRF (r = -0.472, p = 0.031) in the single-leg drop landing test. The CSA of AbH was negatively correlated with contact time (r = -0.478, p = 0.028), and the plantar fascia thickness was positively correlated with jump height (r = 0.615, p = 0.003) and RJI (r = 0.645, p = 0.002) in the repetitive bound jump test. In multivariate regression analysis, only the plantar fascia thickness was associated with RJI (ß = 0.152, 95% confidence interval: 7.219-38.743, p = 0.007). The CSA of FHB may contribute to force attenuation during landing. The thickness of the plantar fascia and CSA of AbH may facilitate jumping high with minimal contact time.

Intrinsic foot muscle hardness is related to dynamic postural stability after landing in healthy young men.

BACKGROUND: The human foot has competent mechanisms for supporting weight and adapting movement to various surfaces; in particular, the toe flexor muscles aid in supporting the foot arches and may be important contributors to postural stability. However, the role of intrinsic foot muscle morphology and structure in the postural control system remains unclear, and the relationship between them is not well known. RESEARCH QUESTION: Are intrinsic foot muscle morphology and toe flexor strength related to static and dynamic postural stability in healthy young men?. METHODS: A total of 27 healthy men aged 19-27 years participated in this study. intrinsic foot muscle morphology included muscle hardness and thickness. Cross-sectional area was measured by ultrasonography at an ankle dorsiflexion angle of 0°. The hardness of the abductor hallucis (AbH), flexor hallucis brevis, and flexor digitorum brevis (FDB) muscles was measured using ultrasound real-time tissue elastography. Static postural stability during single-leg standing on a single force platform with closed eyes was assessed for the right leg. In the assessment of dynamic postural stability, the subjects jumped and landed on single-leg onto a force platform and the dynamic postural stability index (DPSI) was measured. RESULTS: FDB muscle thickness showed a positive correlation with anteroposterior stability index (APSI) (r = 0.398, p = 0.040). AbH muscle hardness was negatively correlated with APSI (r = -0.407, p = 0.035); whereas FDB muscle hardness was positively correlated with DPSI (r = 0.534, p = 0.004), vertical stability index (r = 0.545, p = 0.003), and maximum vertical ground reaction force (r = 0.447, p = 0.020). Multiple regression with forced entry revealed that only DPSI was significantly correlated with FDB muscle hardness (p = 0.003). SIGNIFICANCE: The results indicated that intrinsic foot muscle hardness plays an important role in dynamic postural control among healthy young men, which may enable a more rapid muscular response to changes in condition during jump landing and better performance in balance tasks.

Reliability of Trapezius Muscle Hardness Measurement: A Comparison between Portable Muscle Hardness Meter and Ultrasound Strain Elastography.

Prolonged computer work and smartphone use can cause stiffness of the neck and shoulder muscles, including the trapezius muscle. Hence, muscle hardness quantification is clinically beneficial. The present study aimed to examine the reliability of trapezius muscle hardness measurement using a portable muscle hardness meter and ultrasound strain elastography. Overall, 20 healthy young men participated in this study. Prior to measurement, the participant's subjective symptoms, particularly shoulder muscle stiffness, were rated using an 11-point verbal scale. Furthermore, hardness of the right and left upper trapezius muscles was assessed. In the strain elastography assessment, muscle hardness was evaluated using strain ratio. Results showed that, in quantifying upper trapezius muscle hardness, both portable muscle hardness meter and strain elastography had an excellent intra-tester reliability (>0.9). However, the correlation coefficients between muscle hardness values assessed using a muscle hardness meter and those evaluated with strain elastography did not significantly differ, and the scores for subjective shoulder stiffness did not correspond to muscle hardness values. Therefore, the hardness of the trapezius muscle does not directly reflect the subjective shoulder stiffness. Future studies should thoroughly examine the location of the shoulder stiffness, and check whether it is accompanied by local pain or tenderness.

Value-Added Carp Products: Multi-Class Evaluation of Crisp Grass Carp by Machine Learning-Based Analysis of Blood Indexes.

Crisp grass carp products from China are becoming more prevalent in the worldwide fish market because muscle hardness is the primary desirable characteristic for consumer satisfaction of fish fillet products. Unfortunately, current instrumental methods to evaluate muscle hardness are expensive, time-consuming, and wasteful. This study sought to develop classification models for differentiating the muscle hardness of crisp grass carp on the basis of blood analysis. Out of the total 264 grass carp samples, 12 outliers from crisp grass carp group were removed based on muscle hardness (<9 N), and the remaining 252 samples were used for the analysis of seven blood indexes including hydrogen peroxide (H2O2), glucose 6-phosphate dehydrogenase (G6PD), malondialdehyde (MDA), glutathione (GSH/GSSH), red blood cells (RBC), platelet count (PLT), and lymphocytes (LY). Furthermore, six machine learning models were applied to predict the muscle hardness of grass carp based on the training (152) and testing (100) datasets obtained from the blood analysis: random forest (RF), naïve Bayes (NB), gradient boosting decision tree (GBDT), support vector machine (SVM), partial least squares regression (PLSR), and artificial neural network (ANN). The RF model exhibited the best prediction performance with a classification accuracy of 100%, specificity of 93.08%, and sensitivity of 100% for discriminating crisp grass carp muscle hardness, followed by the NB model (93.75% accuracy, 91.83% specificity, and 94% sensitivity), whereas the ANN model had the lowest prediction performance (85.42% accuracy, 81.05% specificity, and 85% sensitivity). These machine learning methods provided objective, cheap, fast, and reliable classification for in vivo crisp grass carp and also prove useful for muscle quality evaluation of other freshwater fish.

The Effect on Muscle Hardness of Acupuncture Stimulation Using Low-reactive Level Laser Therapy and Silver Spike Point Therapy, along with Stretching.

BACKGROUND AND AIMS: Muscle hardness causes lower activity in athletic practice or sport competition. Increase in muscle hardness often cause injury and muscle fatigue. The aim of this study is to investigate the effect on muscle hardness of acupuncture stimulation using low-reactive level laser therapy (LLLT) and silver spike point (SSP) therapy, along with stimulation by stretching. MATERIALS SUBJECTS AND METHODS: Muscle fatigue was created experimentally, and the effect of LLLT was examined with the indices of muscle hardness and the pennation angle, using ultrasound diagnostic equipment with real-time tissue elastography (RTE) functionality. RESULTS: As a result, a combined use of stretching and SSP therapy was effective on muscle hardness, while LLLT alone had no immediate lowering of muscle hardness. In addition, only the laser stretching group demonstrated a significant decrease in the pennation angle. CONCLUSIONS: This is because an improved local blood flow due to SSP therapy is considered to have relaxed muscle tonus, which boosted metabolism and removed algogenic substances. This became more effective through a combined use of stretching and low-power laser irradiation. Moreover, it was suggested that stimulation of the acupuncture points in the crus could have a further effect on muscle hardness and the pennation angle.

Relationship between trapezius muscle hardness and transverse cervical artery flow in association with neck and upper-back stiffness.

Neck and upper-back stiffness is a common discomfort encountered occasionally in daily life among otherwise healthy subjects. The pathogenesis of this condition could be attributable to increased tension in muscles such as the trapezius muscle (TM). The transverse cervical artery (TCA) is one of the feeding arteries for the TM, and TCA flow is reportedly related to symptoms of neck and upper-back stiffness. This study quantitatively investigated relationships between TM hardness and TCA hemodynamics as evaluated on Doppler sonography. Questionnaires regarding neck and upper-back stiffness, muscle hardness measurements obtained using a muscle hardness meter and examinations of TCA hemodynamics using Doppler sonography were performed on 55 healthy young adults (25 males, 30 females; mean age, 22 ± 2 years). Subjects displaying neck and upper-back stiffness actually exhibited high muscle hardness (median, 14.0; interquartile range (IQR), 12.9-18.0) compared to those without the symptom (median, 12.0; IQR, 9.9-14.0; p = .002). Peak systolic velocity in the TCA on Doppler sonography was lower in subjects with the symptom (median, 65.1 cm/s; IQR 59.6-72.5 cm/s) than in those without the symptom (median, 72.5 cm/s; IQR 66.5-84.2 cm/s; p = .012). Resistive index in the TCA was high (r2  = .605, p = .014) with increasing TM hardness, particularly among male subjects with the symptom. The present study suggests that high resistance and low blood flow velocity in the TCA could be closely associated with the underlying pathogenesis of neck and upper-back stiffness.