Short-time recovery skeletal muscle from dexamethasone-induced atrophy and weakness in old female rats.

Background: Several pathological conditions (atrophy, dystrophy, spasticity, inflammation) can change muscle biomechanical parameters. Our previous works have shown that dexamethasone treatment changes skeletal muscle tone, stiffness, elasticity. Exercise training may oppose the side effects observed during dexamethasone treatment.

The Effect of Different Periodization and Modes of Concurrent Strength and Endurance Training on Double Poling Performance and Body Composition in Adolescent Cross-Country Skiers.

The aim of the study was to compare the effects of different types and periodization of strength training on body composition and maximal aerobic performance in 10-week training period in adolescent XC skiers. Twenty-eight adolescent competitive cross-country skiers, including 10 females (age 17.9 ± 1.

Vitamin C and E Treatment Blunts Sprint Interval Training-Induced Changes in Inflammatory Mediator-, Calcium-, and Mitochondria-Related Signaling in Recreationally Active Elderly Humans.

Sprint interval training (SIT) has emerged as a time-efficient training regimen for young individuals. Here, we studied whether SIT is effective also in elderly individuals and whether the training response was affected by treatment with the antioxidants vitamin C and E. Recreationally active elderly (mean age 65) men received either vitamin C (1 g/day) and vitamin E (235 mg/day) or placebo.

Better Economy on Indoor Track Compared to Treadmill Running With 1% Inclination.

: The purpose of this study was to investigate the differences in metabolic responses between the track and the treadmill (1% inclination) running. The latter is recommended for use in laboratory settings to mimic outdoor running. : Seventeen male endurance athletes (mean 25.

Changes in Body Composition of Old Rats at Different Time Points After Dexamethasone Administration.

Background: Aging leads to changes in skeletal muscle quantity and quality and is accompanied with increase in body mass and fat mass, whereas fat-free mass either decreases or remains unchanged. The body composition of rodents has been an important factor for clinical trials in the laboratory. Glucocorticoids such as dexamethasone are widely used in clinical medicine, but may induce myopathy, characterized by muscle weakness, atrophy, and fatigue.

Glucocorticoid-Induced Changes in Rat Skeletal Muscle Biomechanical and Viscoelastic Properties: Aspects of Aging.

Objectives: The purpose of this study was to estimate the state of tension (tone) and the biomechanical and viscoelastic properties of skeletal muscle in aging rats during the administration of different doses of dexamethasone and to find the relationships among the state of muscle atrophy, muscle strength, and the abovementioned muscle properties.

Methods: Muscle state of tension, biomechanical (elasticity, dynamic stiffness) and viscoelastic (mechanical stress relaxation time, Deborah number) properties (using MyotonPRO, Myoton Ltd, Tallinn, Estonia), lean body mass (BM), and hind limb grip strength were measured before and after the administration of a 10-day treatment with dexamethasone 100 μg/100 g BM (young and old group) and 50 μg/100 g BM (old group).

Results: Muscle elasticity (logarithmic decrement) was lower in old animals (1.

Morphological peculiarities of neuromuscular junctions among different fiber types: Effect of exercise.

The aim of our research was to examine whether there are differences in the morphology of neuromuscular junctions of different types of muscle fibers in rodents, and after their adaptation to six weeks endurance exercise training. After 5-day acclimation, Wistar rats were subjected to run with the speed 35 m/min during 6 week, 5 days per week and the training volume reached 60 min per day. Muscle samples for ultrastructural studies were fixed, dehydrated and embedded in Epon-812.

Physical Education Increases Daily Moderate to Vigorous Physical Activity and Reduces Sedentary Time.

Background: Physical activity (PA) is important to mental and physical health. Physical education (PE) lessons have the potential to increase daily moderate to vigorous PA (MVPA) and reduce sedentary time (SED). We measured MVPA and SED in primary school PE, determined the contribution of PE to daily MVPA and SED, and compared PA on days with and without PE.

Lower Leg Length is Associated with Running Economy in High Level Caucasian Distance Runners.

The aim of the present study was to investigate lower limb anthropometric and composition variables related to running economy (RE) and running performance in a homogeneous group of high level European distance runners. RE at the speeds of 14, 16 and 18 km·h (189 ± 12; 188 ± 11; 187 ± 11 O ml·kg·km) and maximal oxygen uptake (VO) (67.3 ± 2.

Objectively measured sedentary behaviour and moderate and vigorous physical activity in different school subjects: a cross-sectional study.

Background: Evidence shows the positive influence of moderate and vigorous physical activity (MVPA) and negative influence of sedentary time on health and academic achievement. Although schools can significantly contribute to overall physical activity, little is known about MVPA and sedentary behaviour in different school subjects in different grades.

Methods: Physical activity of 646 students from 18 schools (94 classes) and from three school stages (grades 1-9, aged 7-16) was measured with accelerometry for 5 school days.

Role of Myofibrillar Protein Catabolism in Development of Glucocorticoid Myopathy: Aging and Functional Activity Aspects.

Muscle weakness in corticosteroid myopathy is mainly the result of the destruction and atrophy of the myofibrillar compartment of fast-twitch muscle fibers. Decrease of titin and myosin, and the ratio of nebulin and MyHC in myopathic muscle, shows that these changes of contractile and elastic proteins are the result of increased catabolism of the abovementioned proteins in skeletal muscle. Slow regeneration of skeletal muscle is in good correlation with a decreased number of satellite cells under the basal lamina of muscle fibers.

Different Methods Yielded Two-Fold Difference in Compliance with Physical Activity Guidelines on School Days.

Introduction: The aim was to compare the average and the days method in exploring the compliance of children with physical activity guidelines and describe their physical activity patterns in different school day segments.

Methods: Physical activity was objectively measured in 472 children aged 6-13 for one school week. Children were compliant when fulfilling PA recommendations 1) on average over all measured days (average method) or 2) on at least four measured days (days method).

Letter to the editor.

Santos-Concejero and Tucker argued in their letter to the editor that in our study the running economy in achieving superior performance was overlooked due to some methodological aspects. Having given the remarks of Santos-Concejero and Tucker appropriate consideration, in this letter to the editor, we argue that our paper does not downplay the influence of running economy on the determinants of the East African running phenomenon, but rather adds novel insights into the interaction between running economy, maximal oxygen uptake and performance.

Exercise myopathy: changes in myofibrils of fast-twitch muscle fibres.

The purpose of the present study was to determine the relationships between the changes of myofibrils in fast-twitch oxidative-glycolytic (type IIA) fibres and fast-twitch glycolytic (type IIB) muscle fibres, protein synthesis and degradation rate in exercise-induced myopathic skeletal muscle. Exhaustive exercise was used to induce myopathy in Wistar rats. Intensity of glycogenolysis in muscle fibres during exercise, protein synthesis rate, degradation rate and structural changes of myofibrils were measured using morphological and biochemical methods.

Dissociation between running economy and running performance in elite Kenyan distance runners.

The purpose of this study was to investigate the relationship between running economy (RE) and performance in a homogenous group of competitive Kenyan distance runners. Maximal aerobic capacity (VO2max) (68.8 ± 3.

Aging and regenerative capacity of skeletal muscle in rats.

The objective of the study was to examine skeletal muscle regeneration capacity of young and very old rats during autotransplantation. In 3.5 and 30 month-old Wistar rats, gastrocnemius muscle was removed and grafted back to its original bed.

Role of exercise therapy in prevention of decline in aging muscle function: glucocorticoid myopathy and unloading.

Changes in skeletal muscle quantity and quality lead to disability in the aging population. Physiological changes in aging skeletal muscle are associated with a decline in mass, strength, and inability to maintain balance. Glucocorticoids, which are in wide exploitation in various clinical scenarios, lead to the loss of the myofibrillar apparatus, changes in the extracellular matrix, and a decrease in muscle strength and motor activity, particularly in the elderly.

Myosin heavy chain pattern in the Akhal-Teke horses.

This study investigates the myosin heavy chain (MyHC) isoform composition in the gluteus medius muscle of the Akhal-Teke horses using SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis). Fifteen horses aged between 1.5 and 23.

Muscle protein turnover in endurance training: a review.

There has been much debate about skeletal muscle capacity to adapt to long-lasting endurance exercise. Exercise in the aerobic zone of metabolism does not result in hypertrophy of skeletal muscle fibres but increases their oxidative capacity. The duration and intensity of an exercise session determines the time period of depressed muscle protein synthesis and increased degradation rate during the recovery period after exercise.

Review on aging, unloading and reloading: changes in skeletal muscle quantity and quality.

Aging and muscle unloading are associated with a decline in muscle mass, structure, force and changes in the mechanical properties of skeletal muscle. There is a perception that reloading restores muscle architecture and function but differences in the regeneration capacity of intra- and extra-cellular compartments, age dependent susceptibility to muscle damage, particularly in the contractile machinery, make it difficult to attribute the main role of the above mentioned components. This review briefly summarizes studies that examine aging skeletal muscle during unloading and reloading.

Extracellular matrix and myofibrils during unloading and reloading of skeletal muscle.

The aim of the study was to elucidate the effect of unloading and reloading on the collagen expression and synthesis rate of myofibrillar proteins in fast-twitch (FT) muscle in relation to changes in muscle strength and motor activity. Northern blot analysis was used for testing the specificity of cDNA probes and protein synthesis rate was measured according to incorporation of radioactive leucine into different protein fractions. Unloading depresses collagen type I and III (p<0.

Impaired oxidative phosphorylation in overtrained rat myocardium.

The present study was undertaken to characterize and review the changes in energy metabolism in rat myocardium in response to chronic exhaustive exercise. It was shown that a treadmill exercise program applied for six weeks led the rats into a state characterized by decreased performance, loss of body weight and enhanced muscle catabolism, indicating development of overtraining syndrome. Electron microscopy revealed disintegration of the cardiomyocyte structure, cellular swelling and appearance of peroxisomes.

Structural rearrangements in contractile apparatus and resulting skeletal muscle remodelling: effect of exercise training.

This review briefly summarizes studies that examine fast- and slow-twitch skeletal muscles and the ultra- and molecular structure of fibre types, including intrafusal fibres, during adaptation to exercise training. Adaptation capability of skeletal muscle to different types of exercise training depends on rearrangements in the contractile apparatus, mitochondria, other fibre organelles and neuromuscular junctions. Skeletal muscle functional capacity depends on structural changes in fibre organelles and is related to higher centres of motor control as the adaptation process needs information about muscle length and speed of contraction at any time during the training process.

Relationship between extracellular matrix, contractile apparatus, muscle mass and strength in case of glucocorticoid myopathy.

The purpose of this study was to evaluate the effect of dexamethasone on the contractile apparatus and extracellular matrix (ECM) components of slow-twitch (ST) soleus (Sol) and fast-twitch (FT) extensor digitorum longus (EDL) muscle. The specific aim was to assess the development of glucocorticoid-induced myopathy on the level of contractile apparatus and ECM, paying attention to the expression of fibrillar forming collagen types I and III and nonfibrillar type IV collagen expression in extracellular compartment of muscle. Degradation of myofibrillar proteins increased from 2.

Ageing and dexamethasone associated sarcopenia: peculiarities of regeneration.

The purpose of this study was to assess the development of ageing- and glucocorticoid-related sarcopenia on the level of myofibrillar apparatus, paying attention to the synthesis (SR) and degradation rate (DR) of contractile proteins, muscle strength, and daily motor activity. We also wanted to test the effect of ageing and dexamethasone (Dex) excess on the regeneration peculiarities of skeletal muscle autografts. Four and 30-month-old male rats of the Wistar strain were used.