Triathlon involves three different modes of endurance events, swim, bike and run, consecutively. Transitions between events are critical to be successful in the sport; however, many triathletes report impaired running performance due to adverse residual effects from cycling. One of the strategies that triathletes use to manage the adverse effects is to use a bicycle with a more vertical seat post angle. There is limited evidence that support the effectiveness of such bicycle geometry, but many of these studies lacks ecological validity. Twelve triathletes and cyclists completed a 20-km simulated course with instrumentations for 3D motion, kinetic, and electromyographic analyses under two different seat post angle settings: shallow (ROAD) and steep (TRI). Series of paired-t tests were used for statistical analysis. Results indicated cycling mechanics between two seat post angle conditions were similar; however, the steep condition resulted in time-delay in muscle activation and pedal force application. There was no significant difference in cycling performance. The athletes were able to retain relatively consistent pedaling techniques with modification of seat post angle.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Title: Assessment of the activity of the shoulder girdle muscles during static period of climbing movement. Objectives: The aim of the study is to determinate the electromyographic activity of shoulder fixators during natural and corrected climbing grip. The second aim is to compare this activity between the group of climbers and nonclimbers. Methods: The research involved 6 people, 3 climbers and 3 nonclimbers. The surface electromyography had been chosen as an objectification method. Measurements were perfomed during 4 static situation with two variants (natural and corected position). We tested these muscles: m. pectoralis major, m.sternocleidomastoideus, horní, střední a dolní část svalu m.trapezius, m.serratus anterior. The average amplitude normalizated to maximal voluntary contraction (MVC) was evaluated. Results: The significantly lower average amplitude was measured for the middle trapezius (18,4 ± 8,9 % MVC) in natural position (average of all positions) than in position corrected (35,3 ± 11,8 % MVC). For the lower trapezius, the average amplitude in natural position (30,1 ± 13,8 % MVC) was measured significantly lower too than in corrected position (61,7 ± 15,4 % MVC). Conclusions: The measurement results showed that, the EMG activity of the middle and lower m. trapezius was during...

Title: EMGs of Back Muscles in Relation with Different Settings of the Straps of Backpacks Objectives: The aim of this study is to compare the electrical activity of chosen muscles during the gait with student backpack and during the different types of placing the backpack on the back in the vertical plane. The second aim is to find what it the best type of the backpack placement on the back based on the electrical activity. Methods: This thesis is an analytical-experimental research. In the theoretical part, there is a review of available sources relating to existing studies about load carriage, especially backpack carrying. It is preferentially about school type of backpaks, the recommended load limit, the way of placing a backpack on the back and the way of placing a load in the backpack. In the experimental part, there are methods used during experiment. The surface electromyografy was chosen as a experimental method. M. trapezius pars descendens, m. erector spinae and m. rectus abdomis were chosen for recording the EMG signal. The data were recorded during the gait with the backpack of 10% of proband's weight and during 3 different types of backpack placement. The upper type of placement was placed with the centre of the backpack in the level of seventh thoracic vertebra (T7), the middle type...

Title: H-reflex, depending on the position of the joint Aim: The aim of this study is to determine whether the position of the ankle joint influences the parameters of the soleus muscle H-reflex. We are interested in a change of amplitude, latency and threshold of the H-reflex. Method: To measure H-reflex, we have used surface elektromygraphy. We examined two different positions of the foot in probands lying on the bed on their stomach. The first position was with the feet out of bed, around 90 degrees at the ankle joint (rest position). At the second position, the foot moved the bed and was in position in plantar flexion. Stimulation were performed over the tibial nerve in the popliteal fossa. The response, we recorded the surface electrode over the soleus muscle. Results: By changing the position of the ankle from rest to plantar flexion there was no statistically significant changes in amplitude, latency or threshold of the H-reflex. In plantar flection, we found a reduction of Hmax/Mmax ratio, which is probably due to reduced excitability alpha motoneurons through reciprocal ihibition from stretched muscle of the leg. Keywords: H-reflex, soleus muscle, joint position, surface EMG

Název práce: Náborová křivka H-reflexu v diagnostice radikulárních syndromů Cíle práce: Ověření spolehlivosti vyšetření náborové křivky H-reflexu a M-vlny diagnostice kompresivní radikulopatie Metody práce: U 24 osob s jednostranným kořenový syndromem S1 byl vyšetřen H-reflex m. soleus oboustranně bipolární stimulací n.tibialis v popliteální jamce. Elektromyografický signál byl digitalizován a následně byla hodnocena data pro asymptomatickou a symptomatickou končetinu. Hodnoceny byly prahy pro vyvolání H-reflexu a M-vlny, latence a amplitudy H-reflexu a M-vlny, strmost náborové křivky, její maxima Hmax. a Mmax. a poměr Hmax/Max . Tyto hodnoty pro symptomatickou stranu a asymptomatickou stranu byly statisticky porovnány. Výsledky: Výsledky měření potvrdily, že vyšetření náborové křivky H-reflexu je vhodnou diagnostickou metodou k objektivizaci radikulopatie S1. Na symptomatické straně došlo k signifikantnímu poklesu Mmax., Hmax, poměru Hmax/Mmax a sklonu náborové křivky H-reflexu. Klíčová slova: radikulopatie, EMG, H-reflex, M-vlna, náborová křivka

" Electroencephalogram (EEG), Electrocardiogram (ECG), and Electromyogram (EMG) bio-potential signals are commonly recorded in clinical practice. Typically, patients are connected to a bulky and mains-powered instrument, which reduces their mobility and creates discomfort. This limits the acquisition time, prevents the continuous monitoring of patients, and can affect the diagnosis of illness. Therefore, there is a great demand for low-power, small-size, and ambulatory bio-potential signal acquisition systems. Recent work on instrumentation amplifier design for bio-potential signals can be broadly classified as using one or both of two popular techniques: In the first, an AC-coupled signal path with a MOS-Bipolar pseudo resistor is used to obtain a low-frequency cutoff that passes the signal of interest while rejecting large dc offsets. In the second, a chopper stabilization technique is designed to reduce 1/f noise at low frequencies. However, both of these existing techniques lack control of low-frequency cutoff. This thesis presents the design of a mixed- signal integrated circuit (IC) prototype to provide complete, programmable analog signal conditioning and analog-to-digital conversion of an electrophysiologic signal. A front-end amplifier is designed with low input referred noise of 1 uVrms, and common mode rejection ratio 102 dB. A novel second order sigma-delta analog- to-digital converter (ADC) with a feedback integrator from the sigma-delta output is presented to program the low-frequency cutoff, and to enable wide input common mode range of ¡Ãƒâ€œ0.3 V. The overall system is implemented in Jazz Semiconductor 0.18 um CMOS technology with power consumption 5.8 mW from ¡Ãƒâ€œ0.9V power supplies. "

In this study, we used a custom made quadrifilar needle electrode and multichannel electromyography (EMG) software tool to decompose EMG signals and investigate the behavior of motor unit discharge rate (MUDR) of concurrently active motor units in patients with amyotrophic lateral sclerosis (ALS). Decomposition is a technique used to break down the complex EMG signal into its constituent motor units. A motor unit is a single alpha motor neuron and all the muscle fibers it innervates. ALS is a progressive degenerative disorder of both the upper and lower motor neurons. We recorded four differentially amplified EMG signals from the first dorsal interosseous (FDI) muscle of six ALS patients (four with predominant lower motor neuron pathology and two with predominant upper motor neuron pathology) and seven control subjects. Recordings were made from force contractions of 20 and 50% of maximum voluntary contraction (MVC). All control subjects were between the ages of 40 and 70 years and were examined by a practicing physiatrist for exclusion criteria including neuromuscular disorders or any medications that might affect muscle activity. We observed differences in initial firing rates and variability of active motor units between control subjects and ALS patients. Furthermore we observed differences in firing rates and variability of active motor units between ALS patients with predominant upper motor neuron pathology and ALS patients with predominant lower motor neuron pathology. Initial motor unit firing rates for control subjects were 16.22 +/- 2.06 Hz at 20% MVC and 19.79 +/- 1.66 Hz at 50% MVC. As expected, initial motor unit firing rates from patients with predominant lower motor neuron pathology were higher than those of control subjects; 18.87 +/- 4.73 Hz at 20% MVC and 24.28 +/- 5.01 Hz at 50% MVC. ALS patients with predominant upper motor neuron pathology, as expected, had initial motor unit firing rates that were lower than those observed in control subjects; 9.22 +/- 1.68 Hz at 20% MVC and 12.83 +/- 2.26 Hz at 50% MVC. Motor unit firing rate time series in ALS patients with predominant upper motor neuron pathology showed decreased variability, 0.99 +/- 0.17 Hz at 20% MVC and 1.70 +/- 0.52 Hz at 50% MVC, when compared to control subjects, 2.37 +/- 0.67 at 20% MVC and 4.20 +/- 1.00 at 50% MVC. Variability of motor unit firing rate time series in ALS patients with predominant lower motor neuron were high, 3.38 +/- 1.2 Hz at 20% MVC and 4.07 +/- 1.56 Hz at 50% MVC, compared to control subjects. At 50% MVC, motor unit substitution was observed in ALS patients with predominant upper motor neuron pathology despite the contractions lasting just a few seconds. Motor unit action potentials (MUAPs) recorded from patients were polyphasic when compared to those from control subjects, as is characteristically found in practice.