Search results for "Muscle"
showing 10 items of 3397 documents
Influence of Female Sex Hormones on Ultra-Running Performance and Post-Race Recovery: Role of Testosterone
2021
In recent years, increasing numbers of women have participated in extremely long races. In adult males, there is a clear association between physiological levels of endogenous sex hormones and physical performance. However, the influence of plasmatic sex hormones and the effects of different types of hormonal contraception (HC) on the modulation of physical performance in adult females remain to be fully clarified. Eighteen female ultra-endurance athletes were recruited to participate in the study. Different variables were studied, including hematological parameters, body mass index, and body composition. Strength measurements were obtained using the squat-jump and hand-grip test. A repeate…
Changes in power curve shapes as an indicator of fatigue during dynamic contractions.
2010
The purpose of this study was to analyze exercise-induced leg fatigue during a dynamic fatiguing task by examining the shapes of power vs. time curves through the combined use of several statistical methods: B-spline smoothing, functional principal components and (supervised and unsupervised) classification. In addition, granulometric size distributions were also computed to allow for comparison of curves coming from different subjects. Twelve physically active men participated in one acute heavy-resistance exercise protocol which consisted of five sets of 10 repetition maximum leg press with 120 s of rest between sets. To obtain a smooth and accurate representation of the data, a basis of …
Physical activity and quality of cardiopulmonary resuscitation: A secondary analysis of the MANI-CPR trial
2021
Abstract Introduction The association between the level of physical activity and quality of cardio-pulmonary resuscitation (CPR) performed by laypeople is unclear. The aim of this study was to evaluate the associations between physical activity level and laypeople performance during an eight-minute scenario of CPR. Materials and methods This study was a secondary analysis of the MANI-CPR Trial. The entire cohort of participants was grouped based on the level of physical activity assessed using the International Physical Activity Questionnaire (IPAQ) into a “low-moderate” level group and a “high” level group. Descriptive statistics were used for unadjusted analysis and multivariate logistic …
Interrelationships between Muscle Structure, Muscle Strength, and Running Economy
2003
The present study was designed to investigate possible differences in running economy (RE) among elite middle-distance runners by examining muscle structure and maximal isometric force (MVC).Ten young male runners ran at six different running speeds. During the running bouts, respiratory gases, and blood lactate were measured. Muscle biopsies were obtained from the vastus lateralis muscle for analyzing fiber type distribution, muscle fiber area, myosin heavy chain (MHC) composition, activities of a number of metabolic enzymes (citrate synthase, lactate dehydrogenase, phosphofruktokinase, and 3-hydroxyacyl-CoA-dehydrogenase), and titin isoforms.Energy expenditure (EE) increased linearly up t…
Effect of chronic unloading and rehabilitation on human Achilles tendon properties: a velocity-encoded phase-contrast MRI study
2008
The objective of this study was to measure and monitor changes in Achilles tendon mechanical properties and force production capability of triceps surae muscles after 4 wk of limb suspension and 6 wk of physical rehabilitation. Five healthy volunteers underwent unilateral lower limb suspension followed by weekly physiotherapy. A velocity-encoded, phase-contrast magnetic resonance imaging (VE-PC-MRI) technique was used to estimate the tendon strain as a function of force produced during the submaximal isometric contractions. After limb suspension, triceps surae muscle strength decreased to 53.2 ± 15.6% (mean ± SD) of the presuspension level ( P < 0.05). Young's modulus, estimated from the…
Interrelationships between electromyographic, mechanical, muscle structure and reflex time measurements in man.
1981
Reaction time (TRT) with its premotor (PMT) and motor time (MT) components, patellar reflex time (TRfT) with its latency (LAT) and motor time (RfMT) were studied together with isometric force production and relaxation time variables in one leg isometric knee extension. These variables were intercorrelated together with muscle biopsy variables taken from m. vastus lateralis. From these computations MT proved to demonstrate significant correlations to rate of isometric force development (RFD) (P less than 0.001), maximum force (P0) (P less than 0.001) and per cent distribution of ST fibers (P less than 0.001). It is speculated that these relationships are determined by the pattern of the moto…
Treadmill versus overground and barefoot versus shod comparisons of triceps surae fascicle behaviour in human walking and running
2013
Studies of human locomotion are commonly performed on a treadmill or overground, as well as with or without footwear. These testing modalities have been suggested to influence kinematics, kinetics and/or spatio-temporal variables differently. However, it is unclear whether they influence contractile behaviour at the level of the muscle fascicles. This has major relevance because results from studies performed with different combinations of the testing modalities are often compared. The present study used ultrasound to examine fascicle behaviour of the medial gastrocnemius (MG) and soleus muscles of ten young, healthy males during walking and running on a treadmill and overground, as well as…
Do bone geometric properties of the proximal femoral diaphysis reflect loading history, muscle properties, or body dimensions?
2019
Abstract Objectives: The aim of this study was to investigate activity‐induced effects from bone geometric properties of the proximal femur in athletic vs nonathletic healthy females by statistically controlling for variation in body size, lower limb isometric, and dynamic muscle strength, and cross‐sectional area of Musculus gluteus maximus. Methods: The material consists of hip and proximal thigh magnetic resonance images of Finnish female athletes (N = 91) engaged in either high jump, triple jump, soccer, squash, powerlifting, endurance running or swimming, and a group of physically active nonathletic women (N = 20). Cross‐sectional bone geometric properties were calculated for the lesse…
Bilateral and Unilateral Neuromuscular Function and Muscle Cross-Sectional Area in Middle-Aged and Elderly Men and Women
1996
Forty-eight healthy men (M) and women (W), divided into two different age groups, i.e., M50 yrs (range 44-57; n = 12), W50 yrs (range 43-57; n = 12), M70 yrs (range 59-75; n = 12), and W70 yrs (range 62-75; n = 12), volunteered as subjects for examination of muscle cross-sectional area (CSA), maximal voluntary forces, force-time curves, and electromyographic activity of the knee extensor muscles during bilateral and unilateral isometric contractions. The maximal bilateral knee extension force and the average CSA values in M50 were greater (p < .05) than in M70 and in W50 were greater (p < .05-.001) than those recorded for W70. The early forces in the force-time curve were greater (p < .05) …
Reducing Body Myopathy with Cytoplasmic Bodies and Rigid Spine Syndrome: A Mixed Congenital Myopathy
2001
At the age of five years a male child started to develop a progressive rigid spine, torsion scoliosis, and flexion contractures of his elbows, knees, hips, and ankles owing to severe proximal and distal muscle weakness. He had three muscle biopsies from three different muscles at ages 7, 11, and 14 years, respectively. Myopathologically, these muscle tissues contained numerous inclusions which, at the ultrastructural level, turned out to be reducing bodies and cytoplasmic bodies, often in close spatial proximity. Similar histological inclusions, although not further identified by histochemistry and electron microscopy, were seen in his maternal grandmother's biopsied muscle tissue who had d…