Skeletal muscle architecture is the structural property of whole muscles that dominates their function. This review describes the basic architectural properties of human upper and lower extremity muscles. The designs of various muscle groups in humans and other species are analyzed from the point of view of optimizing function. Muscle fiber arrangement and motor unit arrangement is discussed in terms of the control of movement. Finally, the ability of muscles to change their architecture in response to immobilization, eccentric exercise, and surgical tendon transfer is reviewed. Future integrative physiological studies will provide insights into the mechanisms by which such adaptations occur. It is likely that muscle fibers transduce both stress and strain and respond by modifying sarcomere number in a way more suited to the new biomechanical environment.

http://billnordt.com/COREANATOMYFUNCTION/FUNCTIONALANDCLINICALSIGNIFICANCE.pdf

Functional and clinical significance of skeletal muscle architecture.

This book is about the processing of information in face-to-face communication when a speaker makes both audible and visible information available to a perceiver. Both auditory and visual sources of information are evaluated and integrated to achieve speech perception. The evaluation of the information source provides information about the strength of alternative interpretations, rather than just all-or-none categorical information, as claimed by “categorical perception” theory. Information sources are evaluated independently; the integration process insures that the least ambiguous sources have the most influences on the judgment. Similar processes occur in a variety of other behaviors, ranging from personality judgments and categorization to sentence interpretation and decision making. The experimental results are consistent with a fuzzy logical model of perception, positing three operations in perceptual (primary) recognition: feature evaluation, feature integration, and pattern classification. Continuously valued features are first evaluated, then integrated and matched against prototype descriptions in memory; finally, an identification decision is made on the basis of the relative goodness-of-match of the stimulus information with the relevant prototype descriptions.

Speech Perception By Ear and Eye: A Paradigm for Psychological Inquiry

This series of reviews focuses on the most important neuromuscular function in many sport performances: the ability to generate maximal muscular power. Part 1, published in an earlier issue of Sports Medicine, focused on the factors that affect maximal power production while part 2 explores the practical application of these findings by reviewing the scientific literature relevant to the development of training programmes that most effectively enhance maximal power production. The ability to generate maximal power during complex motor skills is of paramount importance to successful athletic performance across many sports. A crucial issue faced by scientists and coaches is the development of effective and efficient training programmes that improve maximal power production in dynamic, multi-joint movements. Such training is referred to as ‘power training’ for the purposes of this review. Although further research is required in order to gain a deeper understanding of the optimal training techniques for maximizing power in complex, sportsspecific movements and the precise mechanisms underlying adaptation, several key conclusions can be drawn from this review. First, a fundamental relationship exists between strength and power, which dictates that an individual cannot possess a high level of power without first being relatively strong. Thus, enhancing and maintaining maximal strength is essential when considering the long-term development of power. Second, consideration of movement pattern, load and velocity specificity is essential when designing power training programmes. Ballistic, plyometric and weightlifting exercises can be used effectively as primary exercises within a power training programme that enhances maximal power. The loads applied to these exercises will depend on the specific requirements of each particular sport and the type of movement being trained. The use of ballistic exercises with loads ranging from 0% to 50% of one-repetition maximum (1RM) and/or weightlifting exercises performed with loads ranging from 50% to 90% of 1RM appears to be the most potent loading stimulus for improving maximal power in complex movements. Furthermore, plyometric exercises should involve stretch rates as well as stretch loads that are similar to those encountered in each specific sport and involve little to no external resistance. These loading conditions allow for superior transfer to performance because they require similar movement velocities to those typically encountered in sport. Third, it is vital to consider the individual athlete’s window of adaptation (i.e. the magnitude of potential for improvement) for each neuromuscular factor contributing to maximal power production when developing an effective and efficient power training programme. A training programme that focuses on the least developed factor contributing to maximal power will prompt the greatest neuromuscular adaptations and therefore result in superior performance improvements for that individual. Finally, a key consideration for the long-term development of an athlete’s maximal power production capacity is the need for an integration of numerous power training techniques. This integration allows for variation within power meso-/micro-cycles while still maintaining specificity, which is theorized to lead to the greatest long-term improvement in maximal power.

/pdf/developing-maximal-neuromuscular-power-part-2-training-2zh4zw3rn7.pdf

Developing maximal neuromuscular power: part 2 - training considerations for improving maximal power production.

Skeletal muscle architecture is defined as the arrangement of fibers in a muscle and functionally defines performance capacity. Architectural values are used to model muscle-joint behavior and to make surgical decisions. The two most extensively used human lower extremity data sets consist of five total specimens of unknown size, gender, and age. Therefore, it is critically important to generate a high-fidelity human lower extremity muscle architecture data set. We disassembled 27 muscles from 21 human lower extremities to characterize muscle fiber length and physiologic cross-sectional area, which define the excursion and force-generating capacities of a muscle. Based on their architectural features, the soleus, gluteus medius, and vastus lateralis are the strongest muscles, whereas the sartorius, gracilis, and semitendinosus have the largest excursion. The plantarflexors, knee extensors, and hip adductors are the strongest muscle groups acting at each joint, whereas the hip adductors and hip extensors have the largest excursion. Contrary to previous assertions, two-joint muscles do not necessarily have longer fibers than single-joint muscles as seen by the similarity of knee flexor and extensor fiber lengths. These high-resolution data will facilitate the development of more accurate musculoskeletal models and challenge existing theories of muscle design; we believe they will aid in surgical decision making.

Are Current Measurements of Lower Extremity Muscle Architecture Accurate

A graphics-based software system to develop and analyze models of musculoskeletal structures

Force, velocity, and displacement properties of a muscle are determined in large part by its architectural design. The relative effect of muscle architecture on these physiological variables was studied by determining muscle weight, fiber length, average sarcomere length, and approximate angle of pinnation of 24 cat hind limb muscles. Muscle lengths ranged from 28.3 to 144 mm, whereas fiber lengths ranged from 8.4 to 105.5 mm. Generally, fiber to muscle length ratios were similar throughout a muscle. Estimated angles of pinnation of muscle fibers varied from 0 to 21 degrees with most having an angle of less than 10 degrees. The cross-sectional area of the knee extensors was similar to the knee flexors (16.43 vs. 16.83 cm2) whereas the cross-sectional area of the ankle extensors was more than six times greater than the ankle flexors (18.59 vs. 2.83 cm2). There was a 6.7-fold difference in the maximal force between muscles, when normalized to a constant weight, that could be attributed to architectural features. Ratios of wet weight to predicted maximal tetanic tension for each muscle and muscle group were calculated to compare the relative priority of muscle force versus muscle length-velocity for a given mass of muscle. These ratios varied from 0.4 to 4.84. The ratios suggest that velocity and/or displacement is a priority for the hamstrings, whereas force is a priority for the quadriceps and lower leg muscles. As much as a 12.6-fold difference in maximal velocity between muscles can be attributed to differences in fiber lengths. This can be compared to approximately a 2.5-fold difference in maximal velocity reported to occur as a result of biochemical (intrinsic) differences.

Architecture of the hind limb muscles of cats: functional significance.

<h3>Objective:</h3> Highlight the importance of recognizing bleeding of intramedullary cavernous malformation or cavernoma as a cause of spinal cord lesion. <h3>Background:</h3> Intramedullary spinal cord hemorrhage, or hematomyelia, is a rare cause of acute myelopathy. Vascular malformations, anticoagulation therapy, and other bleeding diathesis are the most common causes. Cavernoma is a vascular malformation made of closely clustered, enlarged capillaries with a single layer of endothelium and without the elements of normal vascular structure or normal intervening brain parenchyma. Although they can bleed, cavernomas have a relatively benign prognosis. Hemorrhage of an intramedullary cavernoma during anticoagulation with warfarin was not previously reported. <h3>Design/Methods:</h3> Nineteen-year-old man with Behçet’s disease taking warfarin for intraventricular thrombus and multiple pulmonary emboli complained of acute back pain, unilateral leg weakness, and urinary retention. He had no personal or family history of vascular malformations. Examination was remarkable for paraplegia, a sensory level at T10, lower limb hyporeflexia and Babinski reflex bilaterally. INR was supratherapeutic at 3.6. CT of head, cervical and thoracic spine was unremarkable. <h3>Results:</h3> MRI of spine showed an enhancing intramedullary lesion at T8–T9, 3.8 cm in length, with surrounding edema. The mixed T1 hyperintensity and T2 hypointensity was suggestive of hemorrhage caused by a cavernoma. Warfarin was reversed with prothrombin complex concentrate. He was not a candidate for neurosurgical intervention. At discharge, the patient had not regained any motor or sensory function. <h3>Conclusions:</h3> This case highlights the need to suspect hematomyelia as a cause of acute myelopathy in a patient taking anticoagulation. While anticoagulation is not contraindicated in patients with known cavernoma, there should be a low threshold for considering the presence of a bleeding intramedullary cavernoma in a patient with acute myelopathy. <b>Disclosure:</b> Dr. Sacks has nothing to disclose. Dr. Treidler has nothing to disclose. 

Robert D. Sacks

Papers

Architecture of the hind limb muscles of cats: functional significance.

A Case of Hematomyelia in a Teenager with Behcet’s Disease due to both Warfarin and Intramedullary Cavernous Malformation (P6-5.029)