Search results for " contraction"

Opposite effects of dopamine on the mechanical activity of circular and longitudinal muscle of human colon.

2020

Background Because dopamine (DA) has gained increasing evidence as modulator of gut motility, we aimed to characterize dopaminergic response in human colon, evaluating function and distribution of dopamine receptors in circular vs longitudinal muscle strips. Methods Mechanical responses to DA and dopaminergic agonists on slow phasic contractions and on basal tone were examined in vitro as changes in isometric tension. RT-PCR was used to reveal the distribution of dopaminergic receptors. Key results In spontaneous active circular muscle, DA induced an increase in the amplitude of slow phasic contractions and of the basal tone, via activation of D1-like receptors. DA contractile responses wer…

Spinal plasticity with motor imagery practice.

2019

KEY POINTS: While a consensus has now been reached on the effect of motor imagery (MI) – the mental simulation of an action – on motor cortical areas, less is known about its impact on spinal structures. The current study, using H‐reflex conditioning paradigms, examined the effect of a 20 min MI practice on several spinal mechanisms of the plantar flexor muscles. We observed modulations of spinal presynaptic circuitry while imagining, which was even more pronounced following an acute session of MI practice. We suggested that the small cortical output generated during MI may reach specific spinal circuits and that repeating MI may increase the sensitivity of the spinal cord to its effects. T…

Physiological and Molecular Adaptations to Strength Training

2018

High muscle contraction forces that lead to gains in muscle function, size, and strength characterize resistance exercise training. The purpose of this chapter is to outline the adaptations in myofiber size and metabolism that occur by stimuli of hormones and local growth factors, mechanical and metabolic stress of muscle tissue, and myofibrillar disruptions induced by a resistance exercise bout. The chapter will highlight the network of intracellular pathways (including mTOR signaling) that ultimately lead to increases in gene expression and protein synthesis. Accumulation of acute exercise responses by systematic training over time modulate the muscle proteome that can be observed as chan…

Smooth muscle and neural dysfunction contribute to different phases of murine postoperative ileus.

2015

Background Postoperative ileus (POI) is characterized by a transient inhibition of gastrointestinal (GI) motility after abdominal surgery mediated by the inflammation of the muscularis externa (ME). The aim of this study was to identify alterations in the enteric nervous system that may contribute to the pathogenesis of POI. Methods Gastrointestinal transit, contractility of isolated smooth muscle strips and inflammatory parameters were evaluated at different time points (1.5 h to 10 days) after intestinal manipulation (IM) in mice. Immune-labeling was used to visualize changes in myenteric neurons. Key Results Intestinal manipulation resulted in an immediate inhibition of GI transit recove…

Neurotrophic and neuroprotective effects of muscle contraction

2016

Background: Physical activity has been shown to be associated with reduced risk of coronary heart disease but the same effect seems to be produced in neurological diseases. Objective: In this review, we focused on the interplay between physical activity and some neurological conditions (Stroke, dementia, epilepsy, headache, Parkinson’ s disease, amyotrophic lateral sclerosis, multiple sclerosis, insomnia, depression and anxiety) with the aim of describing the potential role of physical activity in the prevention of such diseases and the physiological mechanisms involved in these processes. Results: Despite a growing body of evidence which reveals that physical activity is able to reduce the…

2016

In humans, the amount of spinal homonymous recurrent inhibition during voluntary contraction is usually assessed by using a peripheral nerve stimulation paradigm. This method consists of conditioning the maximal M-wave (SM stimulus) with prior reflex stimulation (S1), with 10 ms inter-stimulus interval (ISI). The decrease observed between unconditioned (S1 only) and conditioned (S1+SM) reflex size is then attributed to recurrent inhibition. However, during a voluntary contraction, a superimposed SM stimulation leads to a maximal M-wave followed by a voluntary (V) wave at similar latency than the H-reflex. This wave can therefore interfere with the conditioned H-reflex when two different sti…

Preventive and Therapeutic Role of Muscle Contraction Against Chronic Diseases.

2016

Background: Due to the continuing increase of the elderly population in the western countries, the prevalence of the main chronic diseases (obesity, type 2 diabetes and related metabolic disorders, arterial hypertension, vascular damage due to atherosclerotic process, cancer, chronic obstructive pulmonary disease, neurodegenerative diseases, chronic kidney disease, immune-mediated diseases) is increasing. There is incontrovertible evidence that regular physical activity contributes to the primary and secondary prevention of several chronic diseases and is associated with a reduced risk of premature death. Methods: In this review the most prevalent chronic pathologic conditions are discussed…

Redox modulation of muscle mass and function

2020

Muscle mass and strength are very important for exercise performance. Training-induced musculoskeletal injuries usually require periods of complete immobilization to prevent any muscle contraction of the affected muscle groups. Disuse muscle wasting will likely affect every sport practitioner in his or her lifetime. Even short periods of disuse results in significant declines in muscle size, fiber cross sectional area, and strength. To understand the molecular signaling pathways involved in disuse muscle atrophy is of the utmost importance to develop more effective countermeasures in sport science research. We have divided our review in four different sections. In the first one we discuss t…

Modulation of muscle-tendon interaction in the human triceps surae during an energy dissipation task.

2017

The compliance of elastic elements allows muscles to dissipate energy safely during eccentric contractions. This buffering function is well documented in animal models but our understanding of its mechanism in humans is confined to non-specific tasks, requiring a subsequent acceleration of the body. The present study aimed to examine the behaviour of the human triceps surae muscle-tendon unit (MTU) during a pure energy dissipation task, under two loading conditions. Thirty-nine subjects performed a single-leg landing task, with- and without added mass. Ultrasound measurements were combined with 3D kinematics and kinetics to determine instantaneous length changes of MTUs, muscle fascicles, A…

Hormone replacement therapy improves contractile function and myonuclear organization of single muscle fibres from postmenopausal monozygotic female …

2013

Ageing is associated with a decline in muscle mass and strength leading to increased physical dependency in old age. Postmenopausal women experience a greater decline than men of similar age in parallel with the decrease in female sex steroid hormone production. We recruited six monozygous female twin pairs (55-59 years old) where only one twin pair was on hormone replacement therapy (HRT use = 7.8 ± 4.3 years) to investigate the association of HRT with the cytoplasmic volume supported by individual myonuclei (myonuclear domain (MND) size,) together with specific force at the single fibre level. HRT use was associated with a significantly smaller (∼27%; P < 0.05) mean MND size in muscle fib…