Increased Ankle Plantar Flexor Stiffness Is Associated With Reduced Mechanical Response to Stretch in Adults With CP

Hyperexcitable stretch reflexes are often not present despite of other signs of spasticity in people with brain lesion. Here we looked for evidence that increased resistance to length change of the plantar flexor muscle-fascicles may contribute to a reduction in the stretch reflex response in adults with cerebral palsy (CP). A total of 17 neurologically intact (NI) adults (mean age 36.1; 12 female) and 13 ambulant adults with CP (7 unilateral; mean age 33.1; 5 female) participated in the study. Subjects were seated in a chair with the examined foot attached to a foot plate, which could be moved by a computer-controlled electromotor. An ultrasound probe was placed over the medial aspect of the leg to measure the length of medial gastrocnemius muscle fascicles. Slow (7 deg/s) and fast (200 deg/s) stretches with amplitude 6 deg of the plantar flexors were applied over an ankle range of 70 deg at 10 deg intervals between 60 and 130 deg plantarflexion. It was checked by EMG electrodes that the slow stretches were sufficiently slow not to elicit any activity and that the fast stretches were sufficiently quick to elicit a maximal stretch reflex in both groups. The torque elicited by the stretches was measured together with changes in the length of medial gastrocnemius muscle fascicles. Muscle fascicles increased significantly in length with increasing dorsiflexion position in both populations (p < 0.001), but the fascicles were shorter in the CP population at all positions. Slow stretches elicited significantly larger torque and significantly smaller length change of muscle fascicles as the ankle joint position was moved more towards dorsiflexion in CP than in NI (p < 0.001). Fast stretches elicited larger torque responses at ankle joint positions of 80–100 deg in the NI than in the CP group (p < 0.01). A significant negative correlation was observed between the torque response and muscle fascicle length change to slow stretch in CP (p < 0.05), but not in NI. These findings support that increased passive resistance of the ankle plantar flexor muscle-tendon unit and development of contractures may conceal stretch reflex response in adults with CP. We argue that this should be taken into account in the neurological examination of spasticity.

An automatic fascicle tracking algorithm quantifying gastrocnemius architecture during maximal effort contractions

Background Ultrasound has become a commonly used imaging modality for making dynamic measurements of muscle structure during functional movements in biomechanical studies. Manual measurements of fascicle length and pennation angle are time intensive which limits the clinical utility of this approach while also limiting sample sizes in research. The purpose of this study was to develop an automatic fascicle tracking program to quantify the length and pennation angle of a muscle fascicle during maximal effort voluntary contractions and to evaluate its repeatability between days and reproducibility between different examiners. Methods Five healthy adults performed maximal effort isometric and isokinetic contractions at 30, 120, 210, and 500 degrees per second about their ankle on an isokinetic dynamometer while their medial gastrocnemius muscle was observed using ultrasound. Individual muscle fascicles and the two aponeuroses were identified by the user in the first frame and automatically tracked by the algorithm by three observers on three separate days. Users also made manual measurements of the candidate fascicle for validation. Repeatability within examiners across days and reproducibility across examiners and days were evaluated using intra-class correlation coefficients (ICC). Agreement between manual and automatic tracking was evaluated using the coefficient of multiple correlations (CMC) and root-mean-square error. Supervised automatic tracking, where the program could be reinitialized if poor tracking was observed, was performed on all videos by one examiner to evaluate the performance of automatic tracking in a typical use case. We also compared the performance our program to a preexisting automatic tracking program. Results We found both manual and automatic measurements of fascicle length and pennation angle to be strongly repeatable within examiners and strongly reproducible across examiners and days (ICCs > 0.74). There was greater agreement between manual and automatic measurements of fascicle length than pennation angle, however the mean CMC value was found to be strong in both cases (CMC > 0.8). Supervision of automatic tracking showed very strong agreement between manual and automatic measurements of fascicle length and pennation angle (CMC > 0.94). It also had considerably less error relative to the preexisting automatic tracking program. Conclusions We have developed a novel automatic fascicle tracking algorithm that quantifies fascicle length and pennation angle of individual muscle fascicles during dynamic contractions during isometric and across a range of isokinetic velocities. We demonstrated that this fascicle tracking algorithm is strongly repeatable and reproducible across different examiners and different days and showed strong agreement with manual measurements, especially when tracking is supervised by the user so that tracking can be reinitialized if poor tracking quality is observed.

Passive changes in muscle length

This review, the first in a series of minireviews on the passive mechanical properties of skeletal muscles, seeks to summarize what is known about the muscle deformations that allow relaxed muscles to lengthen and shorten. Most obviously, when a muscle lengthens, muscle fascicles elongate, but this is not the only mechanism by which muscles change their length. In pennate muscles, elongation of muscle fascicles is accompanied by changes in pennation and changes in fascicle curvature, both of which may contribute to changes in muscle length. The contributions of these mechanisms to change in muscle length are usually small under passive conditions. In very pennate muscles with long aponeuroses, fascicle shear could contribute substantially to changes in muscle length. Tendons experience moderate axial strains even under passive loads, and, because tendons are often much longer than muscle fibers, even moderate tendon strains may contribute substantially to changes in muscle length. Data obtained with new imaging techniques suggest that muscle fascicle and aponeurosis strains are highly nonuniform, but this is yet to be confirmed. The development, validation, and interpretation of continuum muscle models informed by rigorous measurements of muscle architecture and material properties should provide further insights into the mechanisms that allow relaxed muscles to lengthen and shorten.

An automatic fascicle tracking algorithm quantifying gastrocnemius architecture during maximal effort contractions

Background. Ultrasound has become the gold-standard for making dynamic measurements of muscle structure during functional movements in biomechanical studies. Manual measurements of fascicle length and pennation angle are time intensive which limits the clinical utility of this approach while also limiting sample sizes. The purpose of this study was to develop a novel tracking paradigm to quantify individual fascicle length and pennation measurements during maximal voluntary contractions and demonstrate is repeatability between days and reproducibility between different examiners. Methods. Five healthy young adults performed maximal isokinetic contractions at 0, 30, 120, 210, and 500 degrees about their ankle on an isokinetic dynamometer while their gastrocnemius muscle was observed using ultrasound. Individual muscle fascicles were identified in the first frame, and tracked using the automatic fascicle tracking algorithm and a manual approach by three observers on three separate days. Repeatability within examiners across days and reproducibility across examiners and days was evaluated using intraclass correlation coefficients. Agreement between manual and automatic tracking was evaluated using the coefficient of multiple correlations. Supervised automatic tracking was performed on all videos by one examiner to evaluate the fidelity of automatic tracking in practice. Results. We found both manual and automatic measurements of fascicle length and pennation angle to be strongly repeatable within examiners and strongly reproducible across examiners and days (ICCs>0.76). There was greater agreement between manual and automatic measurements of fascicle length than pennation angle, however the mean CMC value for both was still found to be strong in both cases (CMC>0.8). Supervision of automatic tracking greatly showed very strong agreement between manual and automatic measurements of fascicle length and pennation angle (CMC>0.94). Conclusions. We have developed a novel automatic fascicle tracking algorithm that quantifies fascicle length and pennation angle of individual muscle fascicles during dynamic contractions across a range of velocities. We demonstrated that this fascicle tracking algorithm is repeatable and reproducible across different examiners and different days and showed strong agreement with manual measurements, especially when tracking is supervised by the user so that tracking can be reinitialized if poor tracking fidelity is observed.

An automatic fascicle tracking algorithm quantifying gastrocnemius architecture during maximal effort contractions

Background. Ultrasound has become the gold-standard for making dynamic measurements of muscle structure during functional movements in biomechanical studies. Manual measurements of fascicle length and pennation angle are time intensive which limits the clinical utility of this approach while also limiting sample sizes. The purpose of this study was to develop a novel tracking paradigm to quantify individual fascicle length and pennation measurements during maximal voluntary contractions and demonstrate is repeatability between days and reproducibility between different examiners. Methods. Five healthy young adults performed maximal isokinetic contractions at 0, 30, 120, 210, and 500 degrees about their ankle on an isokinetic dynamometer while their gastrocnemius muscle was observed using ultrasound. Individual muscle fascicles were identified in the first frame, and tracked using the automatic fascicle tracking algorithm and a manual approach by three observers on three separate days. Repeatability within examiners across days and reproducibility across examiners and days was evaluated using intraclass correlation coefficients. Agreement between manual and automatic tracking was evaluated using the coefficient of multiple correlations. Supervised automatic tracking was performed on all videos by one examiner to evaluate the fidelity of automatic tracking in practice. Results. We found both manual and automatic measurements of fascicle length and pennation angle to be strongly repeatable within examiners and strongly reproducible across examiners and days (ICCs>0.76). There was greater agreement between manual and automatic measurements of fascicle length than pennation angle, however the mean CMC value for both was still found to be strong in both cases (CMC>0.8). Supervision of automatic tracking greatly showed very strong agreement between manual and automatic measurements of fascicle length and pennation angle (CMC>0.94). Conclusions. We have developed a novel automatic fascicle tracking algorithm that quantifies fascicle length and pennation angle of individual muscle fascicles during dynamic contractions across a range of velocities. We demonstrated that this fascicle tracking algorithm is repeatable and reproducible across different examiners and different days and showed strong agreement with manual measurements, especially when tracking is supervised by the user so that tracking can be reinitialized if poor tracking fidelity is observed.

Myometrial myxoidosis: A rare case seen in a patient of primary subfertility

Myxoid mesenchymal lesions of the uterus are generally restricted to tumors. Myometrial myxoidosis is a rare benign tumor of the uterus. We report a case of myometrial myxoidosis diagnosed postoperatively with histopathological report in a 27-year-old female with primary subfertility who had undergone myomectomy and adenomyomectomy. On gross examination the tumor was 13.5x8x2.5 cm in size. Microscopically, it showed interlacing bundles of smooth muscles intersecting each other. Sections from separate tissue showed muscle fascicles which were separated by abundant extracellular mucin producing a striking myxoid appearance (myxoidosis). Only few cases of myometrial myxoidosis have been reported in literature. Of them, some were associated with lupus erythematosus and some with neurofibromatosis.