Search results for "centri"
showing 10 items of 869 documents
Acute change of titin at mid-sarcomere remains despite 8 wk of plyometric training
2014
Purpose: The purpose of this study was to investigate skeletal muscle changes induced by an acute bout of plyometric exercise (PlyEx) both before and after PlyEx training, to understand if titin is affected differently after PlyEx training. Methods: Healthy untrained individuals (N=11) completed the 1stPlyEx (10x10 squat-jumps, 1min rest). Thereafter, 6 subjects completed 8 weeks of PlyEx, while 5 controls abstained from any jumping activity. Seven days after the last training session all subjects completed the 2ndPlyEx. Blood samples were collected before, 6 hours and 1, 2, 3 and 4 days after each acute bout of PlyEx, and muscle biopsies 4 days before and 3 days after each acute bout of Pl…
Force-, EMG-, and elasticity-velocity relationships at submaximal, maximal and supramaximal running speeds in sprinters.
1986
The relationships between ground reaction forces, electromyographic activity (EMG), elasticity and running velocity were investigated at five speeds from submaximal to supramaximal levels in 11 male and 8 female sprinters. Supramaximal running was performed by a towing system. Reaction forces were measured on a force platform. EMGs were recorded telemetrically with surface electrodes from the vastus lateralis and gastrocnemius muscles, and elasticity of the contact leg was evaluated with spring constant values measured by film analysis. Data showed increases in most of the parameters studied with increasing running speed. At supramaximal velocity (10.36 +/- 0.31 m X s-1; 108.4 +/- 3.8%) the…
Relationship between isokinetic performance and ballistic movement
1983
The present experiments were carried out to assess the relationship between the mechanical behaviour of the leg extensor muscles in 12 male athletes during activities of a ballistic type and torque production, during: (1) torque production during isokinetic contraction: (2) ballistic type activities (vertical jumps from statis position = SJ, with counter-movement equal CMJ and after a fall from different heights equal DJ) and (3) a new anaerobic test (Bosco 1983a). This consisted of performing continuous jump work for a certain period of time (e.g., 60 s). Both ballistic activities and anaerobic power tests demonstrated the highest relationship with peak torques when this was developed resp…
Electromechanical delay in skeletal muscle under normal movement conditions.
1979
Electromechanical delays (EMD), the time from onset of EMG activity to change in acceleration or deceleration of the forearm, were studied in concentric and eccentric contractions of biceps and triceps brachii muscles. Horizontal flexion and extension movements were performed at varying speeds by 10 subjects. EMD time in concentric contractions for biceps was 41 +/- 13 ms and for triceps was 26 +/- 11 ms and was not influenced by the velocity of the movement. In eccentric contractions at the slow velocity the biceps EMD time was 38 +/- 13 ms and shortened to 28 +/- 10 ms at the faster velocity. The eccentric triceps EMD, however, was not significantly altered by movement velocity and averag…
EMG power spectrum and features of the superimposed M-wave during voluntary eccentric and concentric actions at different activation levels.
2001
Muscle fiber conduction velocity (CV) may be affected by the level of voluntary activation and by the diameter of the fiber. Both the frequency component of the electromyography (EMG) power spectrum, such the as median frequency (MF) or mean power frequency, and the duration of muscle compound action potential to single supramaximal electrical impulse (maximal M-wave) may be related to CV. The aim of the present study was to examine how changes in the activation level in lengthening and in shortening conditions would affect the EMG power spectrum during voluntary effort, and compare them to changes in M-wave shape in similar conditions. Ten male subjects performed eccentric and concentric k…
Co-activation and tension-regulating phenomena during isokinetic knee extension in sedentary and highly skilled humans.
1996
The aim of this study was to examine isokinetic torque produced by highly skilled (HS) and sedentary (S) human subjects, during knee extension, during maximal voluntary and superimposed electrical activation. To verify the level of activation of agonist (vastus lateralis, VL, and vastus medialis, VM) and antagonist muscles (semi-tendineous, ST), during maximal voluntary activation, their myo-electrical activities were detected and quantified as root mean square (rms) amplitude. Ten HS and ten S subjects performed voluntary and superimposed isometric actions and isokinetic knee extensions at 14 angular velocities (from -120 to 300 degrees*s(-1)). The rms amplitude of each muscle was normaliz…
Arrhythmia profile in acromegaly.
1992
In a controlled study, the cardiac involvement and arrhythmia profile of 32 patients with acromegaly were correlated with endocrine parameters (somatomedine C, growth hormone), clinical score and duration of the disease. Data were compared with those of 50 controls free of cardiac disease. Stress ECG, 24 h Holter monitoring and echocardiography were performed. Supraventricular premature complexes occurred no more often in acromegalics than in controls. Both prevalence and severity of ventricular arrhythmia, however, were significantly higher in patients compared to controls (P less than 0.01). 15/32 (48%) acromegalic patients had complex ventricular arrhythmias (Lown III-IV) as compared wit…
Performance characteristics of Parkour practitioners: Who are the traceurs?
2015
International audience; Parkour is a modern physical activity that consists of using the environment, mostly urban, as a playground of obstacles. The aims of this study were (i) to investigate age, anthropometric and training characteristics of Parkour practitioners, called ‘traceurs’ and (ii) to assess jump performances and muscular characteristics of traceurs, compared to those of gymnasts and power athletes. The mean age of the population of traceurs studied (n = 130) was 19.4 ± 4.3 years, women represented 12.4% of the total field and mean training volume was 8.1 ± 0.5 hours/week. Vertical and long jump performances were analysed on smaller samples of participants (four groups, n = 15 p…
Autologous fat transfer to the cranio-maxillofacial region: updates and controversies.
2009
Abstract Background Autologous fat grafts have gained popularity among Cranio-Maxillofacial surgeons within the past years. Most publications report favourable outcomes but lack quantifiable evidence of graft survival. Objectives To assess autologous fat transfer for facial asymmetry, and review the literature focusing on current indications, techniques, complications, fat survival and patient satisfaction. Patients and methods Nine patients presented facial asymmetry due to onchological resection, congenital anomaly, or craniofacial traumatism. A total of 11 autologous fat transfers were performed. Four procedures followed the Coleman technique; in the other seven procedures, fat centrifug…
Central Versus Peripheral Adaptations Following Eccentric Resistance Training
2002
Aim of the present investigation was to study the effects of an eccentric training on the neuromuscular properties of the plantar-flexor muscles. The experiment was carried out on 14 males divided into two groups (eccentric and control). Eccentric training consisted of six sets of six eccentric contractions at 120 % of one maximal concentric repetition and it was performed four times a week during four weeks. Before and after the 4-wk period, the plantar-flexor torque and the associated electromyographic activity were recorded during voluntary contractions (isometric, concentric and eccentric) and electrically induced contractions (twitch and tetanus), in order to distinguish central from p…