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Neuromuscular Physiology
Published in Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan, Strength and Conditioning in Sports, 2023
Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan
From a gross anatomical aspect, muscle fibers are arranged into two basic structural patterns: fusiform or pennate (also spelled pinnate). The fusiform arrangement makes up most human muscle, with the fibers largely arranged in parallel arrays along the muscle’s longitudinal axis with tendons at the proximal and distal ends. In many of the larger muscles the fibers (and the fascicles) are inserted obliquely into the tendon, and this arrangement resembles a feather (i.e., pennation). Pennate muscle fibers are typically shorter than those of a fusiform muscle and insert on their tendons in several different manners forming uni-, bi-, and multipennate muscles. Fusiform fibers can largely run parallel, converge or form a circular arrangement; the various arrangements of human fusiform and pennate muscle fibers are shown in Figure 1.1.
Electromyograms
Published in A. Bakiya, K. Kamalanand, R. L. J. De Britto, Mechano-Electric Correlations in the Human Physiological System, 2021
A. Bakiya, K. Kamalanand, R. L. J. De Britto
In pennate muscles, the tendons run throughout the length of the muscles. Further, they are categorized into three types: unipennate (all the fascicles are on the same side of the tendon), bipennate (fascicles lie on either side of the tendon) and multipennate (central tendon branches within a pennate muscle). The rectus femoris is a pennate muscle found in thigh.
The movement systems: skeletal and muscular
Published in Nick Draper, Helen Marshall, Exercise Physiology, 2014
A pennate muscle has fascicles that attach obliquely, at a common angle, to the tendon. Due to the angular arrangement, and hence direction of pull of the muscle fibres, contraction of a pennate muscle is unable to reduce its length to the same degree as a parallel muscle. A greater number of myofibrils, however, are found in pennate muscles allowing for a greater development of muscular tension. Pennate muscles, therefore, generally allow a higher force production but a smaller range of movement. Depending on the location of the fascicles in relation to the tendon, a pennate muscle may be classified as unipennate, bipennate or multipennate. A muscle is unipennate when all muscle fibres are on one side of the tendon and bipennate when on both sides of the tendon. Bipennate muscles are much more common, with the rectus femoris muscle of the thigh being a well-known example. In some cases the tendon branches within a pennate muscle and is known as multi-pennate, for example the deltoid muscle of the shoulder.
Modeling of muscular activation of the muscle-tendon complex using discrete element method
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Anthony Roux, Jennyfer Lecompte, Ivan Iordanoff, Sébastien Laporte
With a maximal isometric force of a muscle fiber fixed at Fmax fiber = 0.3 N, a pack of 400 muscle fibers create a maximal isometric force of 400 × 0.3 = 120 N. However, a parallelepiped of 400 muscle fibers gives a maximal isometric force of 104.2 N and a parallelepiped of 400 muscle fibers oriented by 20° gives a maximal isometric force of 68.8 N. The decrease in force is due to the parallelepiped structure, the pennation angle and the influence of the ECM on the mechanical behavior. For a cylindrical structure with the same dimensions (pennation angle = 20°), the maximal isometric force is 37.3 N. This new decrease is linked to the cylindrical geometry and shorter muscle fibers at the external surface of this specific shape. The relationship between the maximal isometric force of the muscle fiber alone and the equivalent MTC of 400 pennate muscle fibers is not obvious; it depends on the behavior of the ECM, the shape of the equivalent MTC and the value of the pennation angle (Winters and Stark 1988; Winter and Challis 2010; Sànchez et al. 2014; Todros et al. 2020).
Loss of selective wrist muscle activation in post-stroke patients
Published in Disability and Rehabilitation, 2020
Hanneke van der Krogt, Ingrid Kouwijzer, Asbjørn Klomp, Carel G.M. Meskers, J. Hans Arendzen, Jurriaan H. de Groot
Tests were performed on a haptic wrist manipulator (Wristalyzer®, Moog FCS, Nieuw Vennep, The Netherlands) [30], on which torque and wrist joint angle were recorded. Participants were comfortably seated on a chair in front of a video screen. The forearm of the participant was positioned horizontally with the elbow in 90° flexion. The hand was strapped to an ellipsoidal shaped handle (Figure 1) to prevent finger flexion and hand closure. The skin at the electrode positions was cleansed with alcohol and lightly abraded with skin preparation gel (SkinPure, Nihon Kohden, Japan). EMG activity of the m. flexor carpi radialis (FCR) and m. extensor carpi radialis longus and brevis (together abbreviated as ECR) was recorded by bipolar parallel bar surface electrodes (Bagnoli® DE-2.1, Ag, single differential, interelectrode distance 10 mm; Bagnoli-8 amplifier, Delsys Inc., Boston, USA). FCR and ECR were chosen to reflect overall muscle activity of wrist flexor and extensors. Both muscles are the less pennate muscles of the lower arm, have good accessibility with surface EMG and are therefore likely to suffer less from measurement artifacts. Two bipolar electrodes were placed on each muscle group to ensure that a signal was available and to compensate for spatial alterations in the affected (atrophic) muscle after stroke [31]. Position, force and EMG were sampled at 2048 Hz using a 16 bit analog-to-digital card (USB 6221, National Instruments, Austin, USA) [29].
The effect of dry needling on spasticity, gait and muscle architecture in patients with chronic stroke: A case series study
Published in Topics in Stroke Rehabilitation, 2018
Sarafraz Hadi, Otadi Khadijeh, Mohammadreza Hadian, Ayoobi Yazdi Niloofar, Gholamreza Olyaei, Bagheri Hossein, Sandra Calvo, Pablo Herrero
Muscle forces and morphometric parameters of the lower limb skeletal muscles have proven to be good determinants for balance and functional mobility (i.e. gait) after a stroke.6 Consequently, changes in morphometric parameters could alter the muscle force generation.7 Gastrocnemius and soleus are among the prime muscles in the lower limb with main role in standing and walking at all speeds,8 and their contributions increase as gait speeds up in stroke patients.9 Besides, gastrocnemius medialis (GM) is the most common pennate muscle affected by spasticity after stroke,10 and therefore, gait function might be disturbed in this group of patients.9 In pennate muscles, fascicles are arranged in parallel and attach with oblique angles to the tendon, and the resultant forces are transmitted at these angles.11 As mentioned in the literature, muscle architecture (i.e. pennation angle and fascicle length measures) affects the muscle function12 and these measures are often used to estimate the amount of force-generating capability in the muscles.13 Due to spasticity, stroke patients tend to hold their ankle joint in plantar flexion (i.e. in the direction of gravity force). Furthermore, immobilization in this position may cause changes in muscle architecture such as shorter fascicle length and larger pennation angle in comparison with normal individual. Changes in muscle fascicle lengths and their pennation angles will affect the physiologic cross-section, and consequently, force generation potential may reduce14,15 in gait cycles. Using ultrasonography imaging is the most useful, feasible and cheap tool for assessing the muscle architecture parameter, and it is possible to detect some.16,17