Search results for " Muscle"
showing 10 items of 1495 documents
Slower Walking Speed in Older Men Improves Triceps Surae Force Generation Ability
2016
Purpose \ud Older adults walk slower than young adults, but it is not known why. Previous research suggests that ankle plantarflexors may have a crucial role in the reduction of walking speed. The purpose of this study was to investigate age-related differences in triceps surae muscle–tendon function during walking to further investigate the role of plantarflexors in the age-related reduction of walking speed.\ud \ud Methods \ud Medial gastrocnemius and soleus muscle fascicle lengths were measured using ultrasound imaging during walking from 13 young (25 ± 4 yr) men at preferred walking speed and from 13 older (73 ± 5 yr) men at preferred speed and at the young men’s preferred speed. Muscle…
Comparison of force-velocity relationships of vastus lateralis muscle in isokinetic and in stretch-shortening cycle exercises
2003
Aim: This study investigated the force–velocity characteristics of the vastus lateralis (VL) muscle fascicle and muscle–tendon unit (MTU) in isolated lengthening and shortening actions, and during natural movement. Methods: Four subjects performed maximal eccentric and concentric knee extensions (60, 120 and 180° s−1). Unilateral counter movement jumps and drop jumps in the sledge apparatus served as natural movements. Vastus lateralis fascicle lengths were determined from ultrasonography. In vivo patellar tendon forces (PTF) were measured with an optic fibre technique. Patellar tendon force was derived to VL force according to the cross-sectional area of the muscle. Force in the directio…
Muscle fascicle and tendon behavior during human locomotion revisited.
2008
High-speed ultrasonography has revealed that, in human locomotion, the nature of fascicle and tendon length changes varies depending on the task, contraction intensity, and the muscles involved. The findings emphasize that the active fascicles of the gastrocnemius muscle are suddenly stretched, although they are shortening. This short-lasting stretch triggers the stretch reflex, timing of which is dependent on running speed.
Three-dimensional architecture of the whole human soleus muscle in vivo
2018
Background Most data on the architecture of the human soleus muscle have been obtained from cadaveric dissection or two-dimensional ultrasound imaging. We present the first comprehensive, quantitative study on the three-dimensional anatomy of the human soleus muscle in vivo using diffusion tensor imaging (DTI) techniques. Methods We report three-dimensional fascicle lengths, pennation angles, fascicle curvatures, physiological cross-sectional areas and volumes in four compartments of the soleus at ankle joint angles of 69 ± 12° (plantarflexion, short muscle length; average ± SD across subjects) and 108 ± 7° (dorsiflexion, long muscle length) of six healthy young adults. Microdissection and…
Die dynamische31Phosphor-Magnetresonanz-Spektroskopie des M. quadriceps: Metabolische Veränderungen unter zwei verschiedenen Belastungsformen
1997
PURPOSE The aim of the present investigation was to examine the metabolism of the quadriceps muscles of normal young individuals using dynamic 31phosphorus magnetic resonance spectroscopy. METHODS 22 normal individuals were examined in a 1.5T-MRT using a 6 cm surface coil. The metabolic changes in the quadriceps muscle as shown by the phosphorus spectrum were evaluated during rest, exercise (isometric and isotonic exercise) and during a 36-second period of recovery. RESULTS The Pi/PCr quotient rose from its resting value of 0.11 +/- 0.02 following exercise to a maximum of 0.83 +/- 0.47 (isometric) or 1.40 +/- 0.59 (isotonic) (difference p = 0.0001). Half-time recovery of Pi/PCr was 35 +/- 1…
Régulation des défenses antioxydantes dans la prévention du déconditionnement musculaire
2019
Musculoskeletal system plays a key role in organism’s well functioning and is responsible for a large variety of functions such as posture, locomotion, balance, and activities of daily life. The quality of the skeletal muscle is therefore capital to maintain quality of life and, in the long term, survival. Hypoactivity and aging are two situations that cause skeletal muscle deconditioning, therefore sharing common characteristics: loss of muscle strength, muscular atrophy and MyHC redistribution, as well as IMAT accumulation. To date, there is plenty of evidence supporting a causative link between oxidative stress phenomenon and muscle deconditioning. The two studies exposed in this thesis …
Differential influence of peripheral and systemic sex steroids on skeletal muscle quality in pre- and postmenopausal women
2011
Aging is associated with gradual decline of skeletal muscle strength and mass often leading to diminished muscle quality. This phenomenon is known as sarcopenia and affects about 30% of the over 60-year-old population. Androgens act as anabolic agents regulating muscle mass and improving muscle performance. The role of female sex steroids as well as the ability of skeletal muscle tissue to locally produce sex steroids has been less extensively studied. We show that despite the extensive systemic deficit of sex steroid hormones in postmenopausal compared to premenopausal women, the hormone content of skeletal muscle does not follow the same trend. In contrast to the systemic levels, muscle t…
Global gene expression profiles in skeletal muscle of monozygotic female twins discordant for hormone replacement therapy
2010
Summary Aging is accompanied by inexorable loss of muscle tissue. One of the underlying causes for this is the massive change in the hormonal milieu of the body. The role of a female sex steroid – estrogen – in these processes is frequently neglected, although the rapid decline in its production coincides with a steep deterioration in muscle performance. We recruited 54- to 62-year-old monozygotic female twin pairs discordant for postmenopausal hormone replacement therapy (HRT, n = 11 pairs; HRT use 7.3 ± 3.7 years) from the Finnish Twin Cohort to investigate the association of long-term, estrogen-based HRT with skeletal muscle transcriptome. Pathway analysis of muscle transcript profiles r…
Effect of Prolonged Physical Training on the Development of Connective Tissues in Growing Mice
1975
A rapid progress has taken place in the field of connective tissue chemistry during recent years. The structure and metabolism of collagen, elastin, glycosaminoglycans and pro-. teoglycans of different connective tissues have been extensively investigated. One of the main observations has been that large differences exist between various connective tissues [12]. For example, four different forms of collagen have been identified. The collagens in bone, cartilage, skin and basement membrane have either different amino acid composition in the a-chains or contain one or two similar a-chains in the triple helix. The scope of the connective tissue research has been extended also to skeletal muscl…
Importance of sarcopenia parameter changes after living donor liver transplantation
2017
The systemic role of muscle tissue is strengthened by the large system of hormones, chemokines and other mediators that constitute a dense network of communication between the skeletal muscle and the liver (1,2). This, associated with the evidence of a progressive malnutrition and depletion of muscle mass in end-stage liver disease (ESLD) patients, has led many to study the role of sarcopenia and its systemic effects in this setting, and to identify it as critical risk factor for post- liver transplantation (LT) mortality (3-5). Englesbe and colleagues found a direct correlation between central sarcopenia, measured by computerized tomography (CT), the total area of the psoas muscle (psoas a…