-
Cells May 2022Research over almost 40 years has established that reactive oxygen species are generated at different sites in skeletal muscle and that the generation of these species... (Review)
Review
Research over almost 40 years has established that reactive oxygen species are generated at different sites in skeletal muscle and that the generation of these species is increased by various forms of exercise. Initially, this was thought to be potentially deleterious to skeletal muscle and other tissues, but more recent data have identified key roles of these species in muscle adaptations to exercise. The aim of this review is to summarise our current understanding of these redox signalling roles of reactive oxygen species in mediating responses of muscle to contractile activity, with a particular focus on the effects of ageing on these processes. In addition, we provide evidence that disruption of the redox status of muscle mitochondria resulting from age-associated denervation of muscle fibres may be an important factor leading to an attenuation of some muscle responses to contractile activity, and we speculate on potential mechanisms involved.
Topics: Muscle Contraction; Muscle, Skeletal; Oxidation-Reduction; Reactive Oxygen Species
PubMed: 35626735
DOI: 10.3390/cells11101698 -
Biomedical Engineering Online Jul 2022Advances in sports medicine, rehabilitation applications and diagnostics of neuromuscular disorders are based on the analysis of skeletal muscle contractions. Recently,...
BACKGROUND
Advances in sports medicine, rehabilitation applications and diagnostics of neuromuscular disorders are based on the analysis of skeletal muscle contractions. Recently, medical imaging techniques have transformed the study of muscle contractions, by allowing identification of individual motor units' activity, within the whole studied muscle. However, appropriate image-based simulation models, which would assist the continued development of these new imaging methods are missing. This is mainly due to a lack of models that describe the complex interaction between tissues within a muscle and its surroundings, e.g., muscle fibres, fascia, vasculature, bone, skin, and subcutaneous fat. Herein, we propose a new approach to overcome this limitation.
METHODS
In this work, we propose to use deep learning to model the authentic intra-muscular skeletal muscle contraction pattern using domain-to-domain translation between in silico (simulated) and in vivo (experimental) image sequences of skeletal muscle contraction dynamics. For this purpose, the 3D cycle generative adversarial network (cycleGAN) models were evaluated on several hyperparameter settings and modifications. The results show that there were large differences between the spatial features of in silico and in vivo data, and that a model could be trained to generate authentic spatio-temporal features similar to those obtained from in vivo experimental data. In addition, we used difference maps between input and output of the trained model generator to study the translated characteristics of in vivo data.
RESULTS
This work provides a model to generate authentic intra-muscular skeletal muscle contraction dynamics that could be used to gain further and much needed physiological and pathological insights and assess and overcome limitations within the newly developed research field of neuromuscular imaging.
Topics: Computer Simulation; Image Processing, Computer-Assisted; Muscle Contraction
PubMed: 35804415
DOI: 10.1186/s12938-022-01016-4 -
Computer Methods in Biomechanics and... Jun 2023Pelvic floor disorders affect 24% of US women, and elevated intra-abdominal pressure may cause pelvic injury through musculoskeletal strain. Activity restrictions meant...
Pelvic floor disorders affect 24% of US women, and elevated intra-abdominal pressure may cause pelvic injury through musculoskeletal strain. Activity restrictions meant to reduce pelvic strain after traumatic events, such as childbirth, have shown little benefit to patients. Reported high variability in abdominal pressure suggests that technique plays a substantial role in pressure generation. Understanding these techniques could inform evidence-based recommendations for protective pelvic care. We hypothesized use of a motion-capture methodology could identify four major contributors to elevated pressure: gravity, acceleration, abdominal muscle contraction, and respiration. Twelve women completed nineteen activities while instrumented for whole body motion capture, abdominal pressure, hip acceleration, and respiration volume. Correlation and partial least squares regression were utilized to determine primary technique factors that increase abdominal pressure. The partial least squares model identified two principal components that explained 59.63% of relative intra-abdominal pressure variability. The first component was primarily loaded by hip acceleration and relative respiration volume, and the second component was primarily loaded by flexion moments of the abdomen and thorax. While reducing abdominal muscle use has been a primary strategy in protective pelvic floor care, the influence of hip acceleration and breathing patterns should be considered with similar importance in future work.
Topics: Humans; Female; Pressure; Pelvic Floor; Abdomen; Muscle Contraction; Respiration
PubMed: 35837994
DOI: 10.1080/10255842.2022.2100220 -
American Journal of Physiology.... May 2024The force drop after transcranial magnetic stimulation (TMS) delivered to the motor cortex during voluntary muscle contractions could inform about muscle relaxation...
The force drop after transcranial magnetic stimulation (TMS) delivered to the motor cortex during voluntary muscle contractions could inform about muscle relaxation properties. Because of the physiological relation between skeletal muscle fiber-type distribution and size and muscle relaxation, TMS could be a noninvasive index of muscle relaxation in humans. By combining a noninvasive technique to record muscle relaxation in vivo (TMS) with the gold standard technique for muscle tissue sampling (muscle biopsy), we investigated the relation between TMS-induced muscle relaxation in unfatigued and fatigued states, and muscle fiber-type distribution and size. Sixteen participants (7F/9M) volunteered to participate. Maximal knee-extensor voluntary isometric contractions were performed with TMS before and after a 2-min sustained maximal voluntary isometric contraction. Vastus lateralis muscle tissue was obtained separately from the participants' dominant limb. Fiber type I distribution and relative cross-sectional area of fiber type I correlated with TMS-induced muscle relaxation at baseline ( = 0.67, adjusted = 0.01; = 0.74, adjusted = 0.004, respectively) and normalized TMS-induced muscle relaxation as a percentage of baseline ( = 0.50, adjusted = 0.049; = 0.56, adjusted = 0.031, respectively). The variance in the normalized peak relaxation rate at baseline (59.8%, < 0.001) and in the fatigue resistance (23.0%, = 0.035) were explained by the relative cross-sectional area of fiber type I to total fiber area. Fiber type I proportional area influences TMS-induced muscle relaxation, suggesting TMS as an alternative method to noninvasively inform about skeletal muscle relaxation properties. Transcranial magnetic stimulation (TMS)-induced muscle relaxation reflects intrinsic muscle contractile properties by interrupting the drive from the central nervous system during voluntary muscle contractions. We showed that fiber type I proportional area influences the TMS-induced muscle relaxation, suggesting that TMS could be used for the noninvasive estimation of muscle relaxation in unfatigued and fatigued human muscles when the feasibility of more direct method to study relaxation properties (i.e., muscle biopsy) is restricted.
Topics: Humans; Transcranial Magnetic Stimulation; Electric Stimulation; Muscle, Skeletal; Muscle Relaxation; Muscle Fatigue; Muscle Contraction; Isometric Contraction; Muscle Fibers, Skeletal; Electromyography
PubMed: 38525536
DOI: 10.1152/ajpregu.00174.2023 -
Journal of Neural Engineering Sep 2022The study of human neuromechanical control at the motor unit (MU) level has predominantly focussed on electrical activity and force generation, whilst the link between...
The study of human neuromechanical control at the motor unit (MU) level has predominantly focussed on electrical activity and force generation, whilst the link between these, i.e. the muscle deformation, has not been widely studied. To address this gap, we analysed the kinematics of muscle units in natural contractions.We combined high-density surface electromyography (HDsEMG) and ultrafast ultrasound (US) recordings, at 1000 frames per second, from the tibialis anterior muscle to measure the motion of the muscular tissue caused by individual MU contractions. The MU discharge times were identified online by decomposition of the HDsEMG and provided as biofeedback to 12 subjects who were instructed to keep the MU active at the minimum discharge rate (9.8 ± 4.7 pulses per second; force less than 10% of the maximum). The series of discharge times were used to identify the velocity maps associated with 51 single muscle unit movements with high spatio-temporal precision, by a novel processing method on the concurrently recorded US images. From the individual MU velocity maps, we estimated the region of movement, the duration of the motion, the contraction time, and the excitation-contraction (E-C) coupling delay.Individual muscle unit motions could be reliably identified from the velocity maps in 10 out of 12 subjects. The duration of the motion, total contraction time, and E-C coupling were 17.9±5.3 ms, 56.6±8.4 ms, and 3.8±3.0 ms (= 390 across ten participants). The experimental measures also provided the first evidence of muscle unit twisting during voluntary contractions and MU territories with distinct split regions.The proposed method allows for the study of kinematics of individual MU twitches during natural contractions. The described measurements and characterisations open new avenues for the study of neuromechanics in healthy and pathological conditions.
Topics: Biomechanical Phenomena; Electromyography; Humans; Isometric Contraction; Motor Neurons; Muscle Contraction; Muscle, Skeletal
PubMed: 36001952
DOI: 10.1088/1741-2552/ac8c6c -
European Journal of Applied Physiology Apr 2023Hamstring strain injuries may occur due to differential fatigue and compromised mechanical properties among the hamstring muscles. We examined (1) the effect of fatigue...
PURPOSE
Hamstring strain injuries may occur due to differential fatigue and compromised mechanical properties among the hamstring muscles. We examined (1) the effect of fatigue on hamstrings active muscle stiffness, and (2) whether contraction type affects active muscle stiffness changes during a submaximal fatiguing task.
METHODS
Nine healthy males completed 99 submaximal knee flexions in isometric (ISO), concentric (CON), and eccentric (ECC) conditions. We measured the knee flexor maximal voluntary torque (MVT) (pre/post), shear wave velocity (SWV) during contraction and transverse relaxation times (T2) (pre/post) in biceps femoris long head (BFlh), semitendinosus (ST), and semimembranosus (SM) muscles.
RESULTS
MVT decreased substantially after all conditions (- 18.4 to - 33.6%). The average relative torque sustained during the task was lower in CON than ISO and ECC, but absolute torque was similar. SWV interindividual responses were highly variable across muscles and contraction types. On average, BFlh SWV tended to increase in ISO (0.4 m/s, 4.5%, p = 0.064) but decreased in ECC condition (- 0.8 m/s, - 7.7%, p < 0.01). ST SWV decreased in CON (- 1.1 m/s, - 9.0%, p < 0.01), while it remained unchanged in ISO and ECC. SM SWV decreased in CON (- 0.8 m/s, - 8.1%, p < 0.01), but it was unaffected in ISO and variable in ECC.
CONCLUSION
Fatigue has a differential effect on the mechanical properties of the constituent hamstring muscles, as measured with shear wave elastography, depending upon contraction type. We found preliminary evidence that BFlh is more fatigued than ST or SM during eccentric contractions, which may explain its susceptibility to strain injuries.
Topics: Male; Humans; Hamstring Muscles; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Isometric Contraction; Torque; Electromyography
PubMed: 36494585
DOI: 10.1007/s00421-022-05104-0 -
Medical Science Monitor : International... Nov 2020BACKGROUND Temporomandibular disorders (TMD) are accompanied by masticatory muscle-related pain, making it meaningful to assess the stiffness of the masticatory muscles.... (Clinical Trial)
Clinical Trial
BACKGROUND Temporomandibular disorders (TMD) are accompanied by masticatory muscle-related pain, making it meaningful to assess the stiffness of the masticatory muscles. The present study investigated the intra- and inter-operator reliabilities of MyotonPRO for assessing the elasticity of masseter muscles, to determine minimal detectable changes, and to quantify changes in stiffness from conditions of relaxation to maximal contraction. MATERIAL AND METHODS Twenty healthy subjects (10 men and 10 women) were recruited. The stiffness of their masseter muscles was quantified with MyotonPRO in both relaxed and maximal contraction conditions. Two experienced operators (A and B) measured stiffness on the same day, and operator A repeated this procedure 5 days later. RESULTS Intra-rater reliability was good (ICC=0.78) and inter-operator reliability was excellent (ICC=0.95) for assessing masseter muscle stiffness with MyotonPRO. The mean stiffness of the masseter muscle on the dominant side was 369.5 N/m under relaxed conditions and 618.3 N/m at maximum bite force, an increase of 67.4%. Stiffness on the dominant and non-dominant sides did not differ significantly under both conditions (P>0.05). CONCLUSIONS MyotonPRO is a reliable method for quantifying the stiffness of the masseter muscle and monitoring its changes under different contraction conditions.
Topics: Adult; Bite Force; Electromyography; Female; Humans; Male; Masseter Muscle; Muscle Contraction; Observer Variation; Reproducibility of Results
PubMed: 33137025
DOI: 10.12659/MSM.926578 -
Journal of the Mechanical Behavior of... Oct 2022One of the skeletal muscle's exceptional properties is its high damage tolerance in terms of its high toughness, which allows the muscle to withstand cracks of...
One of the skeletal muscle's exceptional properties is its high damage tolerance in terms of its high toughness, which allows the muscle to withstand cracks of millimeter length while maintaining most of its strength (Taylor et al., 2012). In skeletal muscles, damage occurs on different hierarchical levels of the microstructure. We analyze the damage behavior on hierarchy levels 3 (muscle fiber) and 4 (fascicle) on which the most common serious muscle injuries occur. Our model captures damage initiation and rupture of activated muscle fibers resulting from eccentric contractions. We consider the interaction between muscle fibers and endomysium and investigate the influence of the components titin and endomysium on the mechanical behavior in pre-damaged fascicles. Endomysium generally transmits contractile forces. Our results show that high strains in pre-damaged fiber regions are not transferred by the endomysium and, thus, adjacent undamaged fibers are well protected. Moreover, the results show titin's extraordinary stabilization properties of pre-damaged muscle fibers, so that macroscopic strains of fascicles are hardly reduced in case of strongly pre-damaged fibers and intact titin.
Topics: Computer Simulation; Connectin; Muscle Contraction; Muscle Fibers, Skeletal; Muscle, Skeletal
PubMed: 35952441
DOI: 10.1016/j.jmbbm.2022.105386 -
European Journal of Applied Physiology Jun 2023To understand muscle damage in badminton, changes in neuromuscular function were investigated after simulated badminton singles matches performed by ten state-level male...
PURPOSE
To understand muscle damage in badminton, changes in neuromuscular function were investigated after simulated badminton singles matches performed by ten state-level male players.
METHODS
Each participant played eight matches and measurements were taken before, immediately after, and 1 and 24 h after each match. Maximal voluntary isometric contraction (MVC) torque of the knee extensors and flexors, voluntary activation (VA) during MVC and torques generated by doublet (T), 20 (T) and 80 Hz (T) electrical stimulations of the knee extensors were measured from the dominant leg (the racket-hold arm side). Muscle soreness was assessed by a 100-mm visual analogue scale from both legs. The number of lunges performed by each participant in each match was analysed by videos, and its relations to other measures were examined.
RESULTS
Pre-match knee extensor and flexor MVC torques were 278.4 ± 50.8 Nm and 143.0 ± 36.2 Nm, respectively. Knee extensor MVC torque of the dominant leg decreased immediately (12.0 ± 2.9%) and 1 h post-match (16.0 ± 3.2%), but returned to baseline at 24 h post-match. VA (11.4 ± 2.9%), T (13.1 ± 6.0%), T (31.1 ± 12.3%) and T (25.5 ± 7.9%) decreased (p < 0.01) immediately post-match but recovered by 24 h post-match. A significant correlation (r = - 0.64, p < 0.01) was observed between the total number of lunges performed in a match (160-240 times) and the magnitude of decrease in MVC torque (6.4-14.7%). Muscle soreness developed more (p < 0.05) for the dominant (51.5 ± 11.6 mm) than the non-dominant leg (18.8 ± 8.6 mm).
CONCLUSION
Muscle damage induced by singles badminton matches was minimal, but the more the lunges are performed, the greater the neuromuscular fatigue.
Topics: Humans; Male; Myalgia; Muscle Fatigue; Knee; Isometric Contraction; Racquet Sports; Muscles; Muscle, Skeletal; Muscle Contraction; Torque; Electromyography
PubMed: 36763122
DOI: 10.1007/s00421-023-05148-w -
Acta Physiologica (Oxford, England) May 2023Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized, among the others, by muscle weakness. PD patients reach lower values of peak torque...
AIM
Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized, among the others, by muscle weakness. PD patients reach lower values of peak torque during maximal voluntary contractions but also slower rates of torque development (RTD) during explosive contractions. The aim of this study was to better understand how an impairment in structural/mechanical (peripheral) factors could explain the difficulty of PD patients to raise torque rapidly.
METHODS
Participants (PD patients and healthy matched controls) performed maximum voluntary explosive fixed-end contraction of the knee extensor muscles during which dynamic muscle shape changes (in muscle thickness, pennation angle, and belly gearing: the ratio between muscle belly velocity and fascicle velocity), muscle-tendon unit (MTU) stiffness and EMG activity of the vastus lateralis (VL) were investigated. Both the affected (PDA) and less affected limb (PDNA) were investigated in patients.
RESULTS
Control participants reached higher values of peak torque and showed a better capacity to express force rapidly compared to patients (PDA and PDNA). EMG activity was observed to differ between patients (PDA) and controls, but not between controls and PDNA. This suggests a specific neural/nervous effect on the most affected side. On the contrary, MTU stiffness and dynamic muscle shape changes were found to differ between controls and patients, but not between PDA and PDNA. Both sides are thus similarly affected by the pathology.
CONCLUSION
The higher MTU stiffness in PD patients is likely responsible for the impaired muscle capability to change in shape which, in turn, negatively affects the torque rise.
Topics: Humans; Parkinson Disease; Muscle, Skeletal; Tendons; Quadriceps Muscle; Knee Joint; Torque; Muscle Contraction; Isometric Contraction; Electromyography
PubMed: 36876976
DOI: 10.1111/apha.13957