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The spatial distribution of the medial gastrocnemius muscle spindles of 10 male and 10 female rats was analysed under a light microscope, and for the first time, visualised using a 3D model of the muscle. Serial cross‐sections of the medial gastrocnemius muscles were separated into 10 divisions along with the proximo‐distal axis. The muscle spindles of the rat medial gastrocnemius were predominantly...
In the present study, the activity of isolated motor units (MUs) in the rat soleus (SOL) muscle was evoked by stimulation of thin filaments of ventral roots using constant and irregular frequency stimulation patterns. The MUs force, action potentials, and mechanomyograms (MMG) were recorded. MMG profiles were recorded with a laser distance sensor (LDS), categorized and compared with profiles obtained...
INTRODUCTION: There are numerous sex differences concerning male and female skeletal muscles, including muscle mass, the number and diameter of muscle fibers, and number of motor units; however, there is no data concerning the number and density of muscle spindles, which are the most important muscle proprioceptors. AIM(S): The experiments aimed to determine the number of gamma motoneurons, number...
INTRODUCTION: Unfused tetanic contractions of fast motor units exhibit a transitional decline in force following the initial extra-efficient force development, known as sag. Sag is sensitive to changing energy demands and the fuels metabolized to meet these demands. AIM(S): Since different training modes have varying effects on cellular energy systems in muscles, we aimed to determine how endurance,...
INTRODUCTION: Experiments concerning the influence of temperature on mammalian muscles have reported that contractile properties and metabolism are sensitive to the temperature. However, in the literature, there is no information concerning consequences of reduced temperature for the motor unit (MU) contractile properties. Based on available data, we expected predominantly a slowdown in twitch time...
INTRODUCTION: The changes in force of motor units (MUs) following changes in activation pattern still are not fully understood, especially in relation to effects of decreasing rate of stimuli. It is known that at linearly decreasing stimulation frequency the force decrease is slower than expected when comparing to the constant stimulation frequency. AIM(S): The aim of study was the explanation of...
INTRODUCTION: There are considerable differences in a number and density of muscle spindles in various skeletal muscles. Considerable sex differences in muscle mass and diameter of extrafusal muscle fibres suggest that muscle spindle density in muscles and morphometric properties of spindles: the diameter, the number and diameters of intrafusal muscle fibres are also different in males and females...
INTRODUCTION: The relationship between the output force and motor command depends on the intrinsic RESULTS: The mathematical decomposition of unfused tetanic contractions of FF and FR MUs into twitch-shape responses to consecutive stimuli was conducted. The decomposition indicated substantial changes predominantly in force and additionally in time parameters of successive twitch‑like components, responsible...
INTRODUCTION: Obesity and diabetes, with associated conditions termed as metabolic syndrome are growing problem worldwide. Consequences of impaired glucose metabolism affect the whole organism including neuromuscular system. Diabetic neuropathy influences predominantly sensory system and to smaller degree motor system. Additionally, skeletal muscles as involved in glucose metabolism are exposed to...
INTRODUCTION: Repeated short-term and high--intensity exercises with a progressive external load are defined as strength or resistance training, which is responsible for an increase in muscle mass and force. AIM(S): The aim of this study was to determine whether strength training induces adaptive changes in firing properties of motoneurons (MNs) innervating the trained muscles. METHOD(S): The study...
INTRODUCTION: Carnosine (beta-alanyl-L-histidine) is predominantly present in skeletal muscle but also in other excitable tissues. It was suggested that muscle carnosine concentration can decrease with ageing. There is growing evidence that supplementation of carnosine can be effective for the treatment of age related disorders as well as neurological disorders e.g. Alzheimer’s disease or Parkinson’s...
BACKGROUND AND AIMS: The aim of this study was to reveal variability of twitch-shape decomposed components of motor unit tetanic contractions of rat soleus muscle, which is almost exclusively composed of slow motor units (MUs). Moreover, sex differences in ranges of the force amplitude or time parameters of these decomposed twitches were analyzed. METHODS: Experiments were performed on adult Wistar...
BACKGROUND AND AIMS: Different forms of chronic physical activity evoke adaptive changes in the neuromuscular system. Long-lasting strength training, with repeated short-term and highintensity exercises, is responsible for an increase of muscle mass and generation of larger forces. However, adaptations in properties of motoneurons innervating muscles subjected to such training have been unknown so...
BACKGROUND AND AIMS: Motor unit (MU) force is regulated by neural and muscular mechanisms. Recently, effects of carnosine on skeletal muscle contractility have been broadly studied. We found that increased muscle carnosine content by beta-alanine supplementation improved MU contractility. Several studies showed that histidine-free diet decreases carnosine content and causes weight loss, anaemia or...
BACKGROUND AND AIMS: The changes in force of motor units (MUs) following changes in activation pattern are still not well understood, especially in relation to the relaxation course at decreasing rate of stimuli. It is known that at linearly decreasing stimulation rate the force decrease is slower than expected when comparing to the constant stimulation frequency. The present study aimed to verify...
BACKGROUND AND AIMS: Endurance training is based on a repeated, prolonged activation of a large number of muscles. It causes morphological, biochemical and metabolic changes in the muscles and the nervous system. However, there are no data concerning changes in motor unit (MU) contractile properties following endurance training. METHODS: 61 male rats were assigned to 4 groups, untrained – control...
BACKGROUND AND AIMS: Expression of distinct types of myosin heavy chain (MHC) isoforms in skeletal muscle is accepted as one of critical factors providing the molecular basis of muscle fibre functional diversity and plasticity. However, chronic nerve stimulation experiments have provided a strong evidence that modifications in the contractile regulatory and the energy metabolism systems occur much...
The sex differences in the number and morphometric parameters of motoneurons in motor nuclei are poorly known. The aim of this study was to determine the differences in the number and size of alpha and gamma motoneurons of the medial gastrocnemius (MG) muscle in male and female Wistar rats. Retrogradely labelled cell bodies of motoneurons of 6 months old animals were studied following a bath of the...
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