Olivier Buttelli

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The aim of the study was to confirm the hypothesis that the longer a contraction is sustained, the larger are the changes in the spatial distribution of muscle activity. For this purpose, surface electromyographic (EMG) signals were recorded with a 13 x 5 grid of electrodes from the upper trapezius muscle of 11 healthy male subjects during static(More)
A group of 24 subjects performed on a cycle ergometer a fatigue test consisting of four successive all-out sprints against the same braking torque. The subjects were not allowed time to recover between sprints and consequently the test duration was shorter than 30 s. The pedal velocity was recorded every 10 ms from a disc fixed to the flywheel with 360(More)
Eight subjects performed a single allout sprint on a cycle ergometer with strain gauges bonded to the cranks. The crank angle-torque curves of the left and right legs were recorded during ten revolutions using the software package supplied with the ergometer. Torque data were stored every 2° (180 angle-torque data per pedal revolution for each leg). The(More)
PURPOSE This study was designed to compare neuromuscular response between boys and men during sustained maximal voluntary contraction (MVC). METHODS Fifteen boys (YB, 10.5 +/- 0.9 yr) and 12 men (AM, 21.5 +/- 4.5 yr) participated in the experiment. Arm's cross sectional area (CSA) and maximal force (F(max)) of elbow flexor were measured before subjects(More)
During a sustained contraction, electromyographic signals (EMGs) undergo a spectral compression. This fatigue behaviour induces a shift of the mean and the median frequencies to lower frequencies. On the other hand, several studies conclude that the mean/median frequency can increase, decrease or remain constant with an increasing force level. Such(More)
The present study was aimed at investigating differences of maximal strength (F max) of the elbow flexors and characteristics of the surface electromyogram (EMG) between six gymnasts (G) and six untrained (UT) 10-year-old boys during brief and maintained maximal voluntary isometric contraction (MVC). The F max was estimated during 5 s MVC (maximal test, MT)(More)
The kinetics of the torque-velocity (T-ω) relationship after aerobic exercise was studied to assess the effect of fatigue on the contractile properties of muscle. A group of 13 subjects exercised until fatigued on a cycle ergometer, at an intensity which corresponded to 60% of their maximal aerobic power for 50 min (MAP60%); ten subjects exercised until(More)
Mean firing rate estimation is an important step in electromyographic (EMG) signals analysis. Its application is of great interest for the conception and implementation of algorithms in various research domains, ranging from neuromuscular diseases diagnosis to biomechanics. The proposed work is focused on the study of the intrinsic cyclostationary(More)
This work focuses on electromyographic (EMG) signal processing. We propose a new blind approach that aims at detecting the firing rates of the activated motor units. The proposed method is based on the fact that, EMGs can be modelled as second-order cyclostationary signals. After application of a Blind Source Separation (BSS) algorithm, we compute a(More)
The effects of fatigue upon the torque-velocity (T-ω) relationship in cycling were studied in 11 subjects. Fatigue was induced by short exhausting exercise, on a cycle ergometer, consisting of 4 all-out sprints without recovery. The linear (T-ω) relationship was determined during each all-out sprint, before, during and after the exhausting exercise. The(More)