Search results for "electromyography"
showing 10 items of 672 documents
Motor unit discharge rate in dynamic movements of the aging soleus
2014
Aging is related to changes at the muscular level, leading to a decline in motor performance increasing the risk of falling and injury. It seems that the age-related changes in motor unit activation are muscle- and intensity dependent. The purpose of this study was to examine possible differences in soleus motor unit discharge rate (MUDR) in both isometric and dynamic contractions between young and elderly adults. 11 young (YOUNG) and 8 elderly (OLD) males participated in the study. The subjects performed isometric and dynamic plantar flexions while seated in an ankle dynamometer. The force levels studied were 10, 20, 40, 60, 80 and 100% of the isometric (ISO) MVC in ISO and 10, 20 and 40% …
Muscle hypertrophy, strength development, and serum hormones during strength training in elderly women with fibromyalgia.
2005
To examine the effects of strength training on maximal force, cross-sectional area (CSA), and electromyographic (EMG) activity of muscles and serum hormone concentrations in elderly females with fibromyalgia (FM).Twenty-six patients with FM were randomly assigned to a training (FMT; n = 13; mean age 60 years) or a control (FMC; n = 13; 59 years) group. FMT performed progressive strength training twice a week for 21 weeks. The measurements included maximal isometric and concentric leg extension forces, EMG activity of the vastus lateralis and medialis, CSA of the quadriceps femoris, and serum concentrations of testosterone (T), free testosterone (FT), growth hormone (GH), insulin-like growth…
Focusing on Increasing Velocity during Heavy Resistance Knee Flexion Exercise Boosts Hamstring Muscle Activity in Chronic Stroke Patients
2016
Background. Muscle strength is markedly reduced in stroke patients, which has negative implications for functional capacity and work ability. Different types of feedback during strength training exercises may alter neuromuscular activity and functional gains.Objective. To compare levels of muscle activity during conditions of blindfolding and intended high contraction speed with a normal condition of high-intensity knee flexions.Methods. Eighteen patients performed unilateral machine knee flexions with a 10-repetition maximum load. Surface electromyography (EMG) was recorded from the quadrics and hamstring muscles and normalized to maximal EMG (nEMG) of the nonparetic limb.Results. For the …
The use of ultrasound to study muscle–tendon function in human posture and locomotion
2013
Analysis of human movement has traditionally relied on measures such as kinematics, kinetics and electromyography. These measures provide valuable information about movement performance and make it possible to draw inferences about muscle and tendon function. Musculoskeletal models are also used frequently to examine the relationship between joint kinematics and muscle-tendon behaviour, and have provided important insights into both healthy and clinical gait. However, muscles interact with compliant tendons during movement, which complicates interpretation of muscle and tendon function based on external measures such as joint kinematics. Accordingly, methods have been developed that enable …
Neuromuscular fatigue differs following unilateral vs bilateral sustained submaximal contractions
2011
The purpose of the present study was to compare the mechanisms of fatigue induced by a unilateral vs a bilateral submaximal isometric knee extension. Ten physically active men completed two experimental sessions, randomly presented. They were asked to maintain an isometric knee extension force corresponding to 20% of the maximal voluntary contraction (MVC) until task failure with one leg (unilateral) vs two legs (bilateral). MVCs were performed before and after the sustained contraction. Transcutaneous electrical stimuli were used to examine central (voluntary activation) and peripheral (peak doublet force at rest) fatigue on the exercised leg. Time to task failure was significantly shorter…
Changes in motor unit characteristics after eccentric elbow flexor exercise
2010
Morphological evidence suggests that fast-twitch fibers are prone to disruption of their membrane structures by eccentric exercise. However, it is unclear how this is reflected in the discharge rate and action potential propagation of individual motor units, especially at high contraction levels. High-density surface electromyograms were recorded from biceps brachii muscle and decomposed to individual motor unit action potentials at isometric contraction levels between 10% and 75% of maximal voluntary contraction (MVC) before intermittent maximal elbow flexor eccentric exercise, and two hours (2H), two days (2D) and four days (4D) post-exercise. Maximal voluntary force decreased by 21.3±5.6…
Changes in neural drive to calf muscles during steady submaximal contractions after repeated static stretches
2021
Key points: Repeated static-stretching interventions consistently increase the range of motion about a joint and decrease total joint stiffness, but findings on the changes in muscle and connective-tissue properties are mixed. The influence of these stretch-induced changes on muscle function at submaximal forces is unknown. To address this gap in knowledge, the changes in neural drive to the plantar flexor muscles after a static-stretch intervention were estimated. Neural drive to the plantar flexor muscles during a low-force contraction increased after repeated static stretches. These findings suggest that adjustments in motor unit activity are necessary at low forces to accommodate reduct…
Core Muscle Activity, Exercise Preference, and Perceived Exertion during Core Exercise with Elastic Resistance versus Machine
2015
Objectives. To investigate core muscle activity, exercise preferences, and perceived exertion during two selected core exercises performed with elastic resistance versus a conventional training machine.Methods. 17 untrained men aged 26–67 years participated in surface electromyography (EMG) measurements of five core muscles during torso-twists performed from left to right with elastic resistance and in the machine, respectively. The order of the exercises was randomized and each exercise consisted of 3 repetitions performed at a 10 RM load. EMG amplitude was normalized (nEMG) to maximum voluntary isometric contraction (MVC).Results. A higher right erector spinae activity in the elastic exer…
The deltoid muscle: an electromyographical analysis of its activity in arm abduction in various body postures
1992
We have carried out an electromyographical examination of the activity of five different regions of the deltoid muscle during abduction/adduction in various body postures with different biomechanical actions of arm gravity. The results show that the deltoid action is highly differentiated in its different regions and is not restricted only to the generation of an abducting moment in the shoulder joint. There is obviously a biomechanical contribution, mainly by its spinal and clavicular regions, to the stabilization of the glenohumeral joint and to the control of the selected plane of abduction.
Electromyographic Activity Evolution of Local Twitch Responses During Dry Needling of Latent Trigger Points in the Gastrocnemius Muscle: A Cross-Sect…
2019
Abstract Objective Trigger points (TrPs) are hypersensitive spots within taut bands of skeletal muscles that elicit referred pain and motor changes. Among the variety of techniques used for treating TrPs, dry needling is one of the most commonly applied interventions. The question of eliciting local twitch responses (LTRs) during TrP dry needling is unclear. Our main aim was to investigate the evolution of the electromyographic (EMG) peak activity of each LTR elicited during dry needling into latent TrPs of the gastrocnemius medialis muscle. Methods Twenty asymptomatic subjects with latent TrPs in the gastrocnemius medialis muscle participated in this cross-sectional study. Changes in EMG s…