Phenotype transformation toward hypersensitivity to soreness in post-exercise muscle

Reliability, Validity, and Responsiveness of Myotonometric Measurement of Muscle Tone, Elasticity, and Stiffness in Patients With Stroke

This doctoral thesis provides an in-depth analysis of the relationship between occupational factors and musculoskeletal pain among professional cleaners, based on two studies. The first study is a cross-sectional investigation spanning 2012-2018, which examines the associations between lifestyle, physical, and psychosocial factors and the prevalence of low-back pain (LBP) and neck/shoulder pain (NSP) in a sample of 1042 participants. The results show significant associations between lifestyle, physical, and psychosocial factors and the prevalence of LBP and NSP. Specifically, cleaners with obesity (BMI>30) experienced greater pain intensity in both LBP (3.75, 95% CI 3.21-4.28) and NSP (3.54, 95% CI 3.04-4.05) compared to those with a normal weight (2.87, 95% CI 2.49-3.24, P=.001 and 2.89, 95% CI 2.53-3.25, p=.01 respectively). Cleaners experiencing high physical exertion during work showed higher LBP and NSP compared with those experiencing low and moderate physical exertion (P menor 0001). Low recognition from management was also associated with higher LBP and NSP (P menor.05). While other factors such as smoking, leisure physical activity, influence at work, and support from colleagues did not reach statistical significance, their inclusion contributes to a better understanding of the complex interplay of factors impacting musculoskeletal health. The second study examines forearm muscle activity during 9 common cleaning tasks in a real working environment. Seven healthy cleaners participated in this study (age: 35.17 9.62 yr; height: 168.17 8.06 cm; weight: 77.14 13.78 kg; experience: 5.60 3.29 yr). Surface wireless electromyography (EMG) was recorded from 2 muscles on both sides of the upper limb, flexor carpi ulnaris (FCU), and extensor carpi radialis (ECR), and normalized to maximal voluntary isometric contractions (MVIC). Top-3 demanding high-force tasks (90th percentile EMG) were the rough floor, dirty rough floor, and office floor mopping for the FCU, and mopping high walls, ceiling mopping, and baize cleaning for the ECR. Top-3 static work tasks (10th percentile EMG) were mopping low walls, ceiling mopping, and dirty rough floors mopping for the FCU and mopping of high walls, low walls, and ceiling for the ECR. The study identified the forearm muscles most physically demanding work tasks during cleaning tasks. The development of better working tools is recommended to avoid high-force overload as well as prolonged static overload of these muscles in cleaners. By identifying both broad occupational risks and specific task-related muscle strains, these studies encourage the development of interventions such as ergonomic tool development and workplace policies that address the multifactorial demands of the cleaning profession and promote cleaner well-being. RESUMEN Esta tesis doctoral proporciona un análisis exhaustivo de la relación entre factores ocupacionales y el dolor musculoesquelético entre los trabajadores de limpieza profesional, basado en dos estudios fundamentales. El primer estudio es una investigación transversal realizada entre 2012 y 2018, que examina las asociaciones entre factores de estilo de vida, físicos y psicosociales y la prevalencia de dolor lumbar (LBP) y dolor de cuello/hombros (NSP) en una muestra de 1042 participantes. Los resultados muestran asociaciones significativas entre dichos factores y la prevalencia de LBP y NSP. Específicamente, los limpiadores con obesidad (IMC>30) experimentaron una mayor intensidad de dolor tanto en LBP (3,75, IC 95% 3,21-4,28) como en NSP (3,54, IC 95% 3,04-4,05) en comparación con aquellos con un peso normal (2,87, IC 95% 2,49-3,24, P=.001 y 2,89, IC 95% 2,53-3,25, p=.01 respectivamente). Los limpiadores que experimentan una alta exigencia física durante el trabajo mostraron un mayor LBP y NSP en comparación con aquellos que experimentan una exigencia física baja o moderada (P menor.0001). El bajo reconocimiento por parte de la gerencia también se asoció con un mayor LBP y NSP (Pmenor.05). Aunque otros factores como el tabaquismo, la actividad física en el tiempo libre, la influencia en el trabajo y el apoyo entre compañeros de trabajo no alcanzaron significancia estadística, su inclusión contribuye a una mejor comprensión de la compleja interacción de factores que impactan en la salud musculoesquelética. El segundo estudio examina la actividad muscular del antebrazo durante 9 tareas de limpieza comunes en un entorno de trabajo real. Siete limpiadores saludables participaron en este estudio (edad: 35,17 9,62 años; altura: 168,17 8,06 cm; peso: 77,14 13,78 kg; experiencia: 5,60 3,29 años). La electromiografía de superficie inalámbrica (EMG) se registró en 2 músculos en ambos lados del miembro superior, el flexor carpi ulnaris (FCU) y el extensor carpi radialis (ECR), y se normalizó con relación a las contracciones isométricas máximas voluntarias (MVIC). Las tres tareas de alta fuerza más exigentes (percentil 90 de EMG) fueron el fregado de piso rugoso, fregado de piso sucio rugoso y fregado de piso de oficina para el FCU, y el fregado de paredes altas, fregado de techo y limpieza de paños para el ECR. Las tres tareas de trabajo estático superior (percentil 10 de EMG) fueron el fregado de paredes bajas, el fregado de techos y el fregado de pisos sucios y rugosos para el FCU y el fregado de paredes altas, paredes bajas y techos para el ECR. El estudio identificó las tareas de trabajo más exigentes físicamente para los músculos del antebrazo durante las tareas de limpieza. Se recomienda el desarrollo de mejores herramientas de trabajo para evitar la sobrecarga de alta fuerza, así como la sobrecarga estática prolongada de estos músculos en los limpiadores. En conjunto, esta tesis enfatiza la necesidad de un enfoque holístico para abordar los trastornos musculoesqueléticos entre los trabajadores de limpieza. Al identificar tanto los riesgos ocupacionales amplios como las tensiones musculares específicas relacionadas con las tareas, estos estudios contribuyen a la base para intervenciones tales como el desarrollo de herramientas ergonómicas y políticas laborales que aborden las demandas únicas de la profesión de limpieza y promuevan el bienestar de los trabajadores de limpieza.

The aim of this paper is to investigate mechanical functioning of a single skeletal muscle, active within a group of (previously) synergistic muscles. For this purpose, we assessed wrist angle-active moment characteristics exerted by a group of wrist flexion muscles in the rat for three conditions: (i) after resection of the upper arm skin; (ii) after subsequent distal tenotomy of flexor carpi ulnaris muscle (FCU); and (iii) after subsequent freeing of FCU distal tendon and muscle belly from surrounding tissues (MT dissection). Measurements were performed for a control group and for an experimental group after recovery (5 weeks) from tendon transfer of FCU to extensor carpi radialis (ECR) insertion. To assess if FCU tenotomy and MT dissection affects FCU contributions to wrist moments exclusively or also those of neighboring wrist flexion muscles, these data were compared to wrist angle-moment characteristics of selectively activated FCU. FCU tenotomy and MT dissection decreased wrist moments of the control group at all wrist angles tested, including also angles for which no or minimal wrist moments were measured when activating FCU exclusively. For the tendon transfer group, wrist flexion moment increased after FCU tenotomy, but to a greater extent than can be expected based on wrist extension moments exerted by selectively excited transferred FCU. We conclude that dissection of a single muscle in any surgical treatment does not only affect mechanical characteristics of the target muscle, but also those of other muscles within the same compartment. Our results demonstrate also that even after agonistic-to-antagonistic tendon transfer, mechanical interactions with previously synergistic muscles do remain present.

The supination effect of tendon transfer of the flexor carpi ulnaris to the extensor carpi radialis brevis or longus: a cadaveric study.

The mechanical effect of a muscle following agonist-to-antagonist tendon transfers does not always meet the surgeon's expectations. We tested the hypothesis that after flexor carpi ulnaris (FCU) to extensor carpi radialis (ECR) tendon transfer in the rat, the direction (flexion or extension) of the muscle's joint moment is dependent on joint angle. Five weeks after recovery from surgery (tendon transfer group) and in a control group, wrist angle-moment characteristics of selectively activated FCU muscle were assessed for progressive stages of dissection: 1) with minimally disrupted connective tissues, 2) after distal tenotomy, and 3) after maximal tendon and muscle belly dissection, but leaving blood supply and innervations intact. In addition, force transmission from active FCU onto the distal tendon of passive palmaris longus (PL) muscle (a wrist flexor) was assessed. Excitation of control FCU yielded flexion moments at all wrist angles tested. Tenotomy decreased peak FCU moment substantially (by 93%) but not fully. Only after maximal dissection, FCU wrist moment became negligible. The mechanical effect of transferred FCU was bidirectional: extension moments in flexed wrist positions and flexion moments in extended wrist positions. Tenotomy decreased peak extension moment (by 33%) and increased peak flexion moment of transferred FCU (by 41%). Following subsequent maximal FCU dissection, FCU moments decreased to near zero at all wrist angles tested. We confirmed that, after transfer of FCU towards a wrist extensor insertion, force can be transmitted from active FCU to the distal tendon of passive PL. We conclude that mechanical effects of a muscle after tendon transfer to an antagonistic site can be quite different from those predicted based solely on the sign of the new moment arm at the joint.

P605: Peroneal nerve damage after knee dislocation. Clinic, neurophysiology and ultrasound in diagnosis, prognosis, treatment and rehabilitation

The distribution of homonymous and heteronymous recurrent inhibition among the motor nuclei innervating the main muscles of the human upper limb has been investigated in 25 healthy subjects. Homonymous recurrent inhibition was studied with a specially designed electrophysiological method with paired H-reflexes, previously described by Bussel & Pierrot-Deseilligny (1977), combined with a pharmacological study using a cholinergic agonist, the L-acetylcarnitine (Rossi & Mazzocchio 1991). These methods were used to investigate the Flexor Carpi Radialis (FCR), Extensor Carpi Radialis (ECR), Opponens Pollicis (OP) and Abductor Digiti Minimi (ADM) motor nuclei. In the Deltoid, Triceps, Flexor Carpi Ulnaris (FCU) and Extensor Carpi Ulnaris (ECU) motor nuclei in which it was impossible to evoke clearly distinguishable H-reflexes, homonymous recurrent inhibition was studied with the PSTH technique: homonymous recurrent inhibition was found in Deltoid, Triceps, FCR, FCU, ECR, ECU motor nuclei but not in OP and ADM motor nuclei. Heteronymous recurrent inhibition was studied with the PSTH technique in the Deltoid, Biceps, Triceps, FCR, ECR, FCU, ECU, Flexor Digitorum Communis (FDC), Extensor Digitorum Communis (EDC) motor nuclei as well as those innervating the intrinsic muscles of the hand. The following results were obtained: (1) motor neurones innervating muscles acting at digits do not receive any heteronymous recurrent inhibition; (2) motor neurones innervating muscles acting at the wrist give recurrent inhibition to motor nuclei of proximal muscles but do not receive any recurrent projections from the latter; and (3) motor neurones innervating proximal muscles (acting at shoulder or elbow) are interconnected by recurrent inhibition and receive heteronymous recurrent projections from some wrist muscles but not from intrinsic hand muscles.

Stroke is not only associated with muscle weakness, but also associated with reduced muscle fatigue resistance and reduced desaturation during exercise that may be caused by a reduced oxidative capacity and/or microvasculature. Therefore, the objective of the present study was to determine the effects of stroke on muscle mass, fiber size and shape, capillarization and oxidative capacity of the rat m. extensor carpi radialis (ECR) and m. flexor carpi ulnaris (FCU) after a photothrombotic stroke in the forelimb region of the primary sensorimotor cortex. The main observation of the present study was that 4 weeks after induction of stroke there were no significant changes in muscle fiber size and shape. Although there was no significant capillary rarefaction, there was some evidence for remodeling of the capillary bed as reflected by a reduced heterogeneity of capillary spacing (p = 0.006) that may result in improved muscle oxygenation. In the ECR, but not in the FCU, this was accompanied by reduction in muscle fiber oxidative capacity as reflected by reduced optical density of sections stained for succinate dehydrogenase (p = 0.013). The reduced oxidative capacity and absence of significant capillary rarefaction resulted in a capillary to fiber ratio per unit of oxidative capacity that was higher after stroke in the ECR (p = 0.01), but not in the FCU. This suggests that at least during the early stages, stroke is not necessarily accompanied by muscle fiber atrophy, and that stroke-induced reductions in oxidative capacity resulting in relative excess of capillarization are muscle specific.

Effects of tendon and muscle belly dissection on muscular force transmission following tendon transfer in the rat

Quantification of the forearm muscles mechanical properties using Myotonometer: Intra- and Inter-Examiner reliability and its relation with hand grip strength

[Medical Research Council (MRC) 2–3] was detected in the triceps brachii, f lexor carpi ulnaris and median nerve-innervated hand muscles. The flexor carpi radialis and ulnaris, extensor carpi ulnaris and finger flexors were mildly impaired. The shoulder girdle muscles, the biceps brachii, brachioradialis and extensor carpi radialis were spared. The muscle stretch reflexes were normal, except for a diminished left triceps jerk. There was no sensory deficit in the left upper limb. The routine blood test results were normal. The negative results included antiganglioside IgG and IgM antibodies, antinuclear antibodies, antineutrophil cytoplasmic antibodies, HBs antigens and serum Mproteins. Cerebrospinal fluid examination showed a normal cell count and protein content. A 3-day course of intravenous methylprednisolone (20 mg/kg daily) was prescribed, but there were no changes the next day. The patient underwent a 5day intravenous immunoglobulin course (0.4 g/kg daily) from days 7 through 11. Motor strength gradually returned during the regimen. On day 12 he could hold, pick up and release objects with his left hand, which had been useless before treatment. Although moderate left shoulder pain persisted, he went back to work on day 15. On follow-up examinations on day 54 his moDear Sir, Neuralgic amyotrophy is a well-established clinical syndrome characterized by an acute onset of shoulder and arm pain followed by muscular weakness, wasting and variable sensory loss [1] . Most neurophysiological studies have reported features of axonal degeneration [2] , reflecting terminal pathological results rather than the underlying process. We report a patient with neuralgic amyotrophy who was examined within a week after pain onset. The investigative results suggested that, in addition to axonal injury, reversible dysfunction within the brachial plexus played a part in the acute profound weakness.

Cortical Somatosensory Excitability Is Modulated in Response to Several Days of Muscle Soreness

This study aimed to analyze postures that were frequently conducted in manufacturing industry. To find grip strength and muscle activities of each posture, Maximum Voluntary Contraction (MVC) and ElectroMyoGraphy (EMG) were measured. Based on the results of this study, the most appropriate posture could be suggested and used as a basic information for preventing musculoskeletal disorders. Most work-related musculoskeletal disorders have been occurred in the fields of manufacturing industry. According to previous studies, it was reported that the rate of musculoskeletal diseases of upper extremity was higher than that of other body parts. Accordingly, there were many studies about discomfort and grip strength of upper extremity. However, these studies dealt with single selection of wrist, elbow and shoulder. So, it was insufficient for comprehensive studies about upper extremity. And in order to improve the work posture, the physiological changes being generated by the combination of wrist, elbow and shoulder postures should be observed and analyzed. In order to conduct this study, thirty university students who had no records of MSDs involved were recruited. Independent variables were postures of wrist(pronation, neutral, supination), postures of elbow(flexion <TEX>$45^{\circ}$</TEX>, <TEX>$90^{\circ}$</TEX>) and postures of shoulder(flexion <TEX>$0^{\circ}$</TEX>, <TEX>$90^{\circ}$</TEX>). And dependent variables were MVC values and EMG values. Jamar dynamometer and TeleMyo 2400T G2 was used to measure MVC and EMG. MVC and EMG for 12 postures were measured for three second and for three times. Experiment was performed randomly. A 10 minutes rest period was provided after each t. To measure muscle load, the EMG signals of eight muscles (Biceps, Medial triceps, Lateral triceps, Brachioradialis, Extensor carpi ulnaris, Extensor carpi radialis, Flexor carpi ulnaris and Flexor carpi radialis) were evaluated. MVC values and EMG values were analyzed using Minitab ver. 14. The results showed that MVC value was the highest at shoulder <TEX>$0^{\circ}$</TEX>, elbow <TEX>$45^{\circ}$</TEX> and wrist supination. In case of wrist postures, MVC of supination is the highest. In case of elbow and shoulder postures, MVC of flexion <TEX>$45^{\circ}$</TEX> and <TEX>$0^{\circ}$</TEX> was the highest. It was found that there were interaction between wrist and elbow posture under shoulder flexion and between shoulder and wrist under elbow flexion <TEX>$45^{\circ}$</TEX>. In case of the angle of shoulder <TEX>$0^{\circ}$</TEX>, elbow <TEX>$45^{\circ}$</TEX> and wrist supination, the EMG values of four muscles(Medial Triceps, Extensor carpi ulnaris, Extensor carpi radialis, Flexor carpi ulnaris) were the highest. Based on this study, it is worth to note that the combination postures of upper extremity have a large impact on the MVC and EMG. The optimal condition upper extremity was shoulder flexion <TEX>$0^{\circ}$</TEX>, elbow flexion <TEX>$45^{\circ}$</TEX> and wrist supination for preventing work-related musculoskeletal disease.

Objective: The research compares the muscle activity of upper and lower according to the shape and height of handle in sit to stand(STS). Method: The research 20 healthy adults in their twenties who were randomly assigned a different type and height of walker handle. The muscle activity of upper trapezius, biceps, triceps brachii, flexor carpi ulnaris, extensor carpi radialis, rectus femoris, biceps, anterior tibialis and calf STS were measured using wireless electromyogram. The value of the measured electromyogram signal was obtained and the muscle activity was subsequently normalized into the value into maximum voluntary contraction of normality was performed for general features of the subject and repeated two-way ANOVA(analysis of variance) was used for the analysis. Results: The upper trapezius, triceps brachii, flexor carpi ulnaris, rectus femoris, biceps and tibialis anterior showed significant in muscle activity according to the height of the walker, while the extensor carpi radialis and flexor carpi ulnaris showed significant in muscle activity according to the shape of handle. Conclusion: Using walker with lower handle height compared to regular walkers will contribute to preventing unnecessary muscle contraction of upper and enabling effective movement with lower. Moreover, the shape of handle that supports forearm in pronation can be helpful in preventing muscular skeletal damage of wrist that can occur from repeated use of walker.

Short-latency excitatory Ia reflex connections were determined between pairs of human wrist flexor and extensor muscles. Spindle Ia afferents were stimulated by either tendon tap or electrical stimulation. The activity of voluntarily activated single motor units was recorded intramuscularly from pairs of wrist flexor or extensor muscles. Cross-correlation between stimuli and the discharge of the motor units provided a measure of the homonymous or heteronymous excitatory input to a motoneurone. Homonymous motoneurone facilitation was generally stronger than that of the heteronymous motoneurones. The principal wrist flexors, flexor carpi radialis (FCR) and flexor carpi ulnaris (FCU), were tightly connected through a bidirectional short-latency reflex pathway. In contrast, the extensor carpi ulnaris (ECU) and the extensor carpi radialis (ECR) did not have similar connections. ECU motoneurones received no short-latency excitatory Ia input from the ECR. ECR motoneurones did receive excitatory Ia input from ECU Ia afferents; however, its latency was delayed by several milliseconds compared with other heteronymous Ia excitatory effects observed. The wrist and finger extensors were linked through heteronymous Ia excitatory reflexes. The reflex connections observed in humans are largely similar to those observed in the cat, with the exception of heteronymous effects from the ECU to the ECR and from the extensor digitorum communis (EDC) to the ECU, which are present only in humans. The differences in the reflex organization of the wrist flexors versus the extensors probably reflects the importance of grasping.