Remodelling of Skeletal Muscle Extracellular Matrix: Effect of Unloading and Reloading

This chapter summarizes studies that examine remodelling of extracellular matrix (ECM) and role of regulatory factors of ECM during unloading and reloading. Hypokinesia has a catabolic effect on both the contractile apparatus and ECM of the skeletal muscle, causing the formation of muscle atrophy, the decrease of the synthesis of contractile proteins and disturbance of the collagen metabolism. The metabolism of fibrillar and non-fibrillar collagens in ECM plays a crucial role in exercise and sport, influencing the strength development through transmission of contractile force in skeletal muscle. The impairment of motor activity and muscle strength is accompanied by the muscle atrophy. The muscle atrophy caused by inactivity and recovery from atrophy demonstrates the plasticity of muscle. Muscle mass and volume increase in a relatively short time, but the recovery of strength takes much longer and is related with the regeneration of the muscle structures. The recovery period of the contractile apparatus and ECM structures is different in slow-and fast-twitch skeletal muscle

Biological Characteristics of Structural and Functional Remodelling in Skeletal Muscle: Effect of Exercise

Abstract For more than one and a half century, the effect of locomotory activity on skeletal muscle structure and function has been studied. It is clear that these changes depend on the mode of activity. Resistance and endurance exercise training differ in their intensity and duration as well as effects on metabolic pathways, structures of skeletal muscle, protein synthesis and degradation rate, neuromuscular junctions and muscle spindles. The purpose of this review was to compare differences and similarities in structural-functional rearrangements in skeletal muscle in endurance and resistance training and the effect of these changes on endurance and strength capacity. The main purpose of the study was to compare changes in mitochondrial and myofibrillar compartments and also changes in neuromuscular junctions in extra-and intrafusal muscle fibers. The comparison of morpho-functional changes in different skeletal muscle fiber types may help an 252 Teet Seene and Priit Kaasik exercise biologist, sport physician, endurance and strength specialist to better understand the nature of specificity of different training modes on the functional capacity of an organism and build up exercise training strategies for both recreational and top athletes

Koronaarinterventsioonid südame halvenenud pumbafunktsiooniga patsientidel

Südamepuudulikkus on muutumas üha suuremaks tervishoiuprobleemiks kogu arenenud maailmas, haiguse üheks sagedasemaks tekkepõhjuseks on südame isheemiatõbi ja selle tüsistused (1). Südame vähenenud kontraktsioonivõimet on peetud koronaarinterventsioonide vastunäidustuseks ning protseduuride riski suurendavaks teguriks (2, 3). Samas on aga hästi teada müokardi isheemia (hüberneeruva müokardi) osa südamepuudulikkuse tekkes ja progresseerumises (4)

Pacing strategy of the finishers of the world marathon majors series

The purpose of the study was to describe pacing patterns of the finishers of the World Marathon Majors series and the effect of sex and age on the pacing pattern. The finishers of the World Marathon Majors series, a total of 69 814 male runners and 46 856 female runners with finishing time ≤ 6 hours were included in the analysis. Difference in pacing (dev%) was calculated as a difference between the first and second half of the marathon and expressed as a percentage of time. Analysis of variance (ANOVA) was used to evaluate the differences within and between the marathon time groups. The differences between the first and second half of the marathon by sex and age group were analysed using linear regression. The average difference between the first and second half of the marathon was 3.44±2.67% for male and 2.81±2.10% for female runners. Male runners with finishing times of 3:00 (h:min) and females with 4:00 (h:min) or slower had the significantly faster first half of the marathon compared to the evenly paced marathon (p=.038 and p=.001, respectively). Regression analysis revealed that female runners had 0.26% smaller difference between the first and second half of the race compared to male runners (R2=0.256; p<.001) when controlled for age and time group. Also, veterans (40 years and older) paced more evenly compared to non-veterans (R2=0.256; p<.001). In conclusion, irrespective of sex and age, faster finishers maintain a more constant velocity than the slower ones. In addition, women and veterans present more even pacing strategy compared to men and non-veterans, respectively

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. Exercise therapy has shown to be a useful tool for the prevention of different diseases, including glucocorticoid myopathy and muscle unloading in the elderly. The purpose of the paper is to discuss the possibilities of using exercise therapy in the prevention of glucocorticoid caused myopathy and unloading in the elderly and to describe relationships between the muscle contractile apparatus and the extracellular matrix in different types of aging muscles

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. Aging causes a reduction of AMP-activated protein kinase (AMPK) activity as the result of the reduced function of the mitochondrial compartment. AMPK activity increases as a result of increased functional activity. Resistance exercise causes anabolic and anticatabolic effects in skeletal muscle: muscle fibers experience hypertrophy while higher myofibrillar proteins turn over. These changes are leading to the qualitative remodeling of muscle fibers. As a result of these changes, possible maximal muscle strength is increasing. Endurance exercise improves capillary blood supply, increases mitochondrial biogenesis and muscle oxidative capacity, and causes a faster turnover rate of sarcoplasmic proteins as well as qualitative remodeling of type I and IIA muscle fibers. The combination of resistance and endurance exercise may be the fastest way to prevent or decelerate muscle atrophy due to the anabolic and anticatabolic effects of exercise combined with an increase in oxidative capacity. The aim of the present short review is to assess the role of myofibrillar protein catabolism in the development of glucocorticoid-caused myopathy from aging and physical activity aspects

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. Ultra-thin sections were cut from longitudinally and transversely oriented blocs, using 4 blocks from each animal. The area of axon terminals on fast- twitch fibers is 1.5 time large (p&lt;0.001) and the perimeter of terminals is 1.7 time large in comparison with slow- twitch oxidative fibers (p&lt;0.001) in control group. There are correlation between cross-sectional area of different muscle fibers and length of axon terminals (r=0.72), between cross-sectional area and with of axon terminal (r=-0.62), and between turnover rate of contractile proteins and length of axon terminal (r=0.75). Fast remodeling of synapse on oxidative and oxidative-glycolytic muscle fibers during endurance training seems to guarantees the intensive renewal of the structures of muscle fibers with higher oxidative capacity