Indices of Loading and Propulsive Ability in the Gait of Patients With Chronic Stroke With Equinus Foot Deviation: A Correlation Study

In literature, indices of overall walking ability that are based on ground reaction forces have been proposed because of their ease of administration with patients. In this study, we analyzed the correlation between the indices of dynamic loading and propulsion ability of 40 chronic hemiparetic post-stroke patients with equinus foot deviation and a set of clinical assessments of ankle joint deviations and walking ability. Ankle passive and active range of motion (ROM) and triceps surae spasticity were considered, along with walking speed and three complementary scales of walking ability focusing respectively on the need for assistance on functional mobility, including balance and transfers, and the limitation in social participation. The correlation between the ground reaction force-based indices and both clinical and functional variables was carried out using the non-parametric Spearman correlation coefficient. Both indices were correlated to 8 of the 10 investigated variables, thus supporting their use. In particular, the dynamic propulsive ability was correlated with all functional scales (rho = 0.5, p < 0.01), and has the advantage of being a continuous variable. Among clinical assessments, limited ankle ROM affected walking ability the most, while spasticity did not. Since the acquisition of ground reaction forces does not require any patient prepping, the derived indices can be used during the rehabilitation period to quickly detect small improvements that, over time, might lead to the broad changes detectable by clinical scales, as well as to immediately highlight the lack of these improvements, thus suggesting adjustments to the ongoing rehabilitation approach.

Less common synaptic input between muscles from the same group allows for more flexible coordination strategies during a fatiguing task

This study aimed to determine whether neural drive is redistributed between muscles during a fatiguing isometric contraction, and if so, whether the initial level of common synaptic input between these muscles constrains this redistribution. We studied two muscle groups: triceps surae (14 participants) and quadriceps (15 participants). Participants performed a series of submaximal isometric contractions and a torque-matched contraction maintained until task failure. We used high-density surface electromyography to identify the behavior of 1874 motor units from the soleus, gastrocnemius medialis (GM), gastrocnemius lateralis(GL), rectus femoris, vastus lateralis (VL), and vastus medialis(VM). We assessed the level of common drive between muscles in absence of fatigue using a coherence analysis. We also assessed the redistribution of neural drive between muscles during the fatiguing contraction through the correlation between their cumulative spike trains (index of neural drive). The level of common drive between VL and VM was significantly higher than that observed for the other muscle pairs, including GL-GM. The level of common drive increased during the fatiguing contraction, but the differences between muscle pairs persisted. We also observed a strong positive correlation of neural drive between VL and VM during the fatiguing contraction (r=0.82). This was not observed for the other muscle pairs, including GL-GM, which exhibited differential changes in neural drive. These results suggest that less common synaptic input between muscles allows for more flexible coordination strategies during a fatiguing task, i.e., differential changes in neural drive across muscles. The role of this flexibility on performance remains to be elucidated.

Whole Body Muscle Activity During Weightlifting Exercise Evaluated By Positron Emission Tomography

Background: This study investigated the whole-body skeletal muscle activity pattern of hang power clean (HPC), a major weight training exercise, using positron emission tomography (PET). Methods: Twelve college weightlifting athletes performed three sets of HPC 20 times with a barbell set to 40 kg both before and after an intravenous injection of 37 MBq 18F-fluorodeoxyglucose (FDG). PET-computed tomography images were obtained 50 min after FDG injection. Regions of interest were defined within 71 muscles. The standardized uptake value was calculated to examine the FDG uptake of muscle tissue per unit volume, and FDG accumulation was compared to the control group. The Mann–Whitney U-test was used to evaluate the differences in the mean SUV between groups. The difference between SUVs of the right and left muscles was evaluated by a paired t-test. A P-value <0.05 was considered statistically significant.Results: FDG accumulation within the vastus lateralis, vastus intermedius, and vastus medialis was higher than that of the rectus femoris. FDG accumulation within the triceps surae muscle was significantly higher only in the soleus. In the trunk and hip muscles, FDG accumulation of only the erector spinae was significantly increased. In all skeletal muscles, there was no difference between SUVs of the right and left muscles.Conclusions: The monoarticular muscles in the lower limbs were active in HPC. In contrast, deep muscles in the trunk and hip were not active during HPC. HPC is not suitable for core training and needs to be supplemented with other training.

Corticospinal excitability remains unchanged in the presence of residual force enhancement and does not contribute to increased torque production

Background Following stretch of an active muscle, muscle force is enhanced, which is known as residual force enhancement (rFE). As earlier studies found apparent corticospinal excitability modulations in the presence of rFE, this study aimed to test whether corticospinal excitability modulations contribute to rFE. Methods Fourteen participants performed submaximal plantar flexion stretch-hold and fixed-end contractions at 30% of their maximal voluntary soleus muscle activity in a dynamometer. During the steady state of the contractions, participants either received subthreshold or suprathreshold transcranial magnetic stimulation (TMS) of their motor cortex, while triceps surae muscle responses to stimulation were obtained via electromyography (EMG), and net ankle joint torque was recorded. B-mode ultrasound imaging was used to confirm muscle fascicle stretch during stretch-hold contractions in a subset of participants. Results Following stretch of the plantar flexors, an average rFE of 7% and 11% was observed for contractions with subthreshold and suprathreshold TMS, respectively. 41–46 ms following subthreshold TMS, triceps surae muscle activity was suppressed by 19–25%, but suppression was not significantly different between stretch-hold and fixed-end contractions. Similarly, the reduction in plantar flexion torque following subthreshold TMS was not significantly different between contraction conditions. Motor evoked potentials, silent periods and superimposed twitches following suprathreshold TMS were also not significantly different between contraction conditions. Discussion As TMS of the motor cortex did not result in any differences between stretch-hold and fixed-end contractions, we conclude that rFE is not linked to changes in corticospinal excitability.

Triceps Surae Muscle-Tendon Properties as Determinants of the Metabolic Cost in Trained Long-Distance Runners

Purpose: This study aimed to determine whether triceps surae’s muscle architecture and Achilles tendon parameters are related to running metabolic cost (C) in trained long-distance runners.Methods: Seventeen trained male recreational long-distance runners (mean age = 34 years) participated in this study. C was measured during submaximal steady-state running (5 min) at 12 and 16 km h–1 on a treadmill. Ultrasound was used to determine the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and soleus (SO) muscle architecture, including fascicle length (FL) and pennation angle (PA), and the Achilles tendon cross-sectional area (CSA), resting length and elongation as a function of plantar flexion torque during maximal voluntary plantar flexion. Achilles tendon mechanical (force, elongation, and stiffness) and material (stress, strain, and Young’s modulus) properties were determined. Stepwise multiple linear regressions were used to determine the relationship between independent variables (tendon resting length, CSA, force, elongation, stiffness, stress, strain, Young’s modulus, and FL and PA of triceps surae muscles) and C (J kg–1m–1) at 12 and 16 km h–1.Results: SO PA and Achilles tendon CSA were negatively associated with C (r2 = 0.69; p &lt; 0.001) at 12 km h–1, whereas SO PA was negatively and Achilles tendon stress was positively associated with C (r2 = 0.63; p = 0.001) at 16 km h–1, respectively. Our results presented a small power, and the multiple linear regression’s cause-effect relation was limited due to the low sample size.Conclusion: For a given muscle length, greater SO PA, probably related to short muscle fibers and to a large physiological cross-sectional area, may be beneficial to C. Larger Achilles tendon CSA may determine a better force distribution per tendon area, thereby reducing tendon stress and C at submaximal speeds (12 and 16 km h–1). Furthermore, Achilles tendon morphological and mechanical properties (CSA, stress, and Young’s modulus) and triceps surae muscle architecture (GM PA, GM FL, SO PA, and SO FL) presented large correlations with C.

Anatomic variability of the nerves of the triceps surae in early human fetuses

Background. Establishing fetal anatomical variability of intramuscular nerves and their connections plays an important role in the search for and development of new methods for the diagnostic and treatment posterior region of the leg. Objective – to find out the topographic and anatomical features of the innervation of the triceps surae in human fetuses 4-6 months. Methods. The study was performed on 46 human fetuses 81.0-230.0 mm crown-rump length (CRL) length using macromicroscopic preparation, vascular injection, and morphometry. Results. In early human fetuses, the anatomical variability of the distribution of intramuscular nerves in the thickness of the triceps surae was established, which is due to the variability of the structure and topography of the tibial nerve, structural and functional organization of triceps surae, arterial branching and interneural connections in the thickness of the heads of the gastrocnemius and soleus in fetuses of different and the same age groups, and sometimes in the same fetus. Conclusion. The main source of innervation of the triceps surae is the tibial nerve, which can be presented by a single trunk, main and additional trunks, or several independent trunks. The nerves in the thickness of the triceps are unevenly distributed. The highest concentration of muscular branches of the tibial nerve is determined in the medial head of the gastrocnemius and the medial part of the soleus. Information on fetal topography of intramuscular nerves in the thickness of the right and left triceps surae, as well as forms of their anatomical variability, both in fetuses of different and the same age and sometimes in the same fetus, due to structural-functional organization of the components of the triceps surae, the type of branching of arteries and nerves in the thickness of the heads of the gastrocnemius and soleus. Atypical variants of the topography of the tibial nerve and common fibular nerve in early fetuses, as well as interneural connections in the thickness of the components of the triceps surae, are more common on the right lower leg.

Triceps Surae Muscle Characteristics in Spastic Hemiparetic Stroke Survivors Treated with Botulinum Toxin Type A: Clinical Implications from Ultrasonographic Evaluation

Equinovarus foot is one of the most commonly spasticity related conditions in stroke survivors, leading to an impaired gait and poor functional performances. Notably, spastic muscles undergo a dynamic evolution following typical pathophysiological patterns. Botulinum Neurotoxin Type A (BoNT-A) is the gold standard for focal spasticity treatment, and ultrasound (US) imaging is widely recommended to guide injections and monitor muscle evolution. The role of BoNT-A in influencing muscle fibroadipose degeneration is still unclear. In this study, we analyzed medial gastrocnemius (MG) and soleus (SOL) US characteristics (cross-sectional area, muscle thickness, pennation angle, and mean echo intensity) in 53 patients. MG and SOL alterations, compared to the unaffected side, depend on the spasticity only and not on the BoNT-A treatment. In functionally preserved patients (functional ambulation classification, FAC > 3; modified Ashworth scale, MAS ≤ 2), the ultrasonographic changes of MG compared to ipsilateral SOL observed in the paretic limb alone seems to be due to histological, anatomical, pathophysiological, and biomechanical differences between the two muscles. In subjects with poor walking capability and more severe spasticity, such ipsilateral difference was found in both calves. In conclusion, BoNT-A does not seem to influence muscle degeneration. Similar muscles undergo different evolution depending on the grade of walking deficit and spasticity.

When Antagonist Muscles at the Ankle Interfere with Maximal Voluntary Contraction under Isometric and Anisometric Conditions

Purpose: While resultant maximal voluntary contraction (MVC) is commonly used to assess muscular performance, the simultaneous activation of antagonist muscles could dramatically underestimate the strength of the agonist muscles. While quantification of antagonist torque has been performed in plantar- (PF) and dorsi-flexion (DF) joint in isometric conditions, it has yet to be determined in anisometric (concentric and eccentric) conditions. Methods: The experiment was performed in 9 participants through 2 sessions (reliability). The MVCs in DF and PF were measured in isometric, concentric and eccentric conditions (10&deg;.s-1). Electromyographic (EMG) activities from the soleus, gastrocnemius medialis and lateralis, and tibialis anterior muscles were simultaneously recorded. The EMG biofeedback method was used to quantify antagonist torque, where participants were asked to maintain a level of EMG activity, corresponding to antagonist EMG activity and related to the muscle contraction type, according to a visual EMG bio-feedback displayed on a screen. Results: Resultant torque significantly underestimated agonist torque in DF MVC (30-65%) and to a lesser extent in PF MVC (3%). Triceps surae antagonist torque was significantly modified with muscle contraction type, showing higher antagonist torque in isometric (29 Nm) than eccentric (23 Nm, p &lt; 0.001) and concentric (14 Nm, p &lt; 0.001) conditions and resulting in modification of the DF MVC torque-velocity shape. The difference between DF eccentric and concentric MVC was attenuated when considered agonist torque (12%) rather than resultant torque (45%). Conclusion: Estimation of the antagonist torque in isometric or anisometric condition brings new insights to assessment of muscular performance and could result in costly misinterpretation in strength training and/or rehabilitation programs.

Bilateral multifocal muscular hemorrhage in the triceps surae during antiplatelet therapy: a case report

Hemorrhagic complications are often reported following antiplatelet therapy; however, simultaneous multifocal hemorrhages in both legs are uncommon. The patient was a 75-year-old man diagnosed with ST elevation myocardial infarction who underwent percutaneous coronary intervention in the right coronary artery. He was prescribed oral acetylsalicylic acid and ticagrelor. Three days after initial drug treatment, he complained of bilateral leg pain that was aggravated by walking and moving his ankle across a broad range of motion. No deep vein thrombosis was detected on Doppler ultrasonography; however, muscular hemorrhage was suspected according to musculoskeletal ultrasonography. Multifocal muscular hemorrhage was confirmed in the soleus and gastrocnemius muscles on magnetic resonance imaging. To reduce the risk of bleeding, we changed the medication from ticagrelor to clopidogrel. The patient performed leg elevation exercises, compression, and applied an ice pack. He also performed range of motion exercises and gait training in addition to receiving drug treatment. With these therapies, his pain score improved from 5 to 3 on a visual analog scale, without further complications. Multifocal muscular hemorrhage rarely occurs bilaterally; however, when it does occur, an appropriate treatment plan can be developed based on musculoskeletal ultrasonography.