Search results for " EXERCISE"
showing 10 items of 1621 documents
Neuromuscular fatigue during a long-duration cycling exercise
2002
The effects of prolonged cycling on neuromuscular parameters were studied in nine endurance-trained subjects during a 5-h exercise sustained at 55% of the maximal aerobic power. Torque during maximal voluntary contraction (MVC) of the quadriceps muscle decreased progressively throughout the exercise ( P < 0.01) and was 18% less at the end of exercise compared with the preexercise value. Peak twitch torque, contraction time, and total area of mechanical response decreased significantly ( P < 0.05) after the first hour of exercise. In contrast, changes in M-wave characteristics were significant only after the fourth hour of the exercise. Significant reductions ( P < 0.05) in electro…
Skeletal muscle blood flow and flow heterogeneity during dynamic and isometric exercise in humans
2002
The effects of dynamic and intermittent isometric knee extension exercises on skeletal muscle blood flow and flow heterogeneity were studied in seven healthy endurance-trained men. Regional muscle blood flow was measured using positron emission tomography (PET) and an [15O]H2O tracer, and electromyographic (EMG) activity was recorded in the quadriceps femoris (QF) muscle during submaximal intermittent isometric and dynamic exercises. QF blood flow was 61% ( P = 0.002) higher during dynamic exercise. Interestingly, flow heterogeneity was 13% ( P = 0.024) lower during dynamic compared with intermittent isometric exercise. EMG activity was significantly higher ( P < 0.001) during dynamic e…
Influence of lactate accumulation of EMG frequency spectrum during repeated concentric contractions
1983
One hundred and twenty consecutive maximal leg extensions at a constant angular velocity of 1.5 radians . s-1 were performed by nine physical education students. Integrated electromyographic (IEMG) activity and power spectrum density function (PSDF) of the EMG were recorded from m. vastus lateralis, vastus medialis and m. rectus femoris using bipolar surface electrodes. Muscle biopsies were obtained from m. vastus lateralis before and after exercise. Tissue samples were analyzed for muscle fiber type distribution and lactate and glycogen concentration. Muscle force and IEMG decreased in parallel over the exercise period. Thus, the IEMG/force ratio was unchanged. Mean power frequency (MPF) o…
Electromyographic activity related to aerobic and anaerobic threshold in ergometer bicycling
1985
Electromyographic activity (EMG) of the knee extensor musculature (m. vastus lateralis, m. vastus medialis, m. rectus femoris), triceps surae (m. gastrocnemius, m. soleus) and m. tibialis anterior was studied in ergometer bicycling at five different power outputs around aerobic (AerT) and anaerobic (AnT) thresholds. EMGs were sampled with surface electrodes for ten revolutions at the beginning, in the middle and at the end of each work load and integrated (IEMG) separately for each of the muscles and for the descending (work) and ascending (rest) phase of the revolution. The mean power frequency (MPF) of the power spectral density function for the descending periods was also calculated. The…
Torque decrease during submaximal evoked contractions of the quadriceps muscle is linked not only to muscle fatigue.
2015
International audience; The aim of this study was to analyze the neuromuscular mechanisms involved in the torque decrease induced by submaximal electromyostimulation (EMS) of the quadriceps muscle. It was hypothesized that torque decrease after EMS would reflect the fatigability of the activated motor units (MUs), but also a reduction in the number of MUs recruited as a result of changes in axonal excitability threshold. Two experiments were performed on 20 men to analyze 1) the supramaximal twitch superimposed and evoked at rest during EMS (Experiment 1, n = 9) and 2) the twitch response and torque-frequency relation of the MUs activated by EMS (Experiment 2, n = 11). Torque loss was asses…
Motivation to Physical Exercise in Manual Wheelchair Users With Paraplegia
2020
Background: Motivation could be considered as a critical factor for being and staying physically active in the spinal cord–injured population. Objectives: Our goals were (1) to describe motivation to exercise in people with paraplegia, comparing those who engage in regular physical exercise with those who do not and (2) to establish whether such motivation is related to the type of physical exercise practiced. Methods: This study was quantitative, cross-sectional descriptive research. One-hundred and six participants with chronic paraplegia completed the Spanish version of the Exercise Motivations Inventory (EMI-2). Participants were divided into the non-exerciser group (NEG) and the exerc…
Adverse Cardiovascular Response to Aerobic Exercise Training
2015
AB Purpose: Aerobic exercise training in sedentary individuals improves physical fitness and various cardiovascular (CV) biomarkers. Nevertheless, there has been controversy as to whether exercise training may adversely affect some biomarkers in a small segment of the population. The purpose of this study was to investigate whether clinically significant worsening of CV biomarkers was more prevalent among individuals randomized to a supervised endurance training program as compared with those randomized to a control condition. Methods: Baseline and end of study measurements of fasting insulin (FI), triglycerides (TG), resting systolic blood pressure (SBP), and HDL cholesterol (HDL-C) were o…
Core muscle activity in a series of balance exercises with different stability conditions
2014
Literature that provides progression models based on core muscle activity and postural manipulations is scarce. The purpose of this study was to investigate the core muscle activity in a series of balance exercises with different stability levels and additional elastic resistance. A descriptive study of electromyography (EMG) was performed with forty-four healthy subjects that completed 12 exercises in a random order. Exercises were performed unipedally or bipedally with or without elastic tubing as resistance on various unstable (uncontrolled multiaxial and uniaxial movement) and stable surfaces. Surface EMG on the lumbar multífidus spinae (LM), thoracic multífidus spinae (TM), lumbar erec…
Fast increase of motor cortical inhibition following postural changes in healthy subjects.
2012
BACKGROUND AND AIMS: Postural reactions are associated with changes in the excitability of the motor system. In the present study we investigated the presence of neurophysiological changes of motor cortical areas targeting muscles of the inferior limbs following treatment with a physiotherapy technique aimed to treat postural dysfunctions by stretching postural muscles, global postural reeducation (GPR). METHODS: Twenty healthy subjects were evaluated with paired-transcranial magnetic stimulation (TMS) of the motor cortex and recording of motor evoked potentials (MEPs) from peripheral muscles of the inferior limb before and after two GPR manoeuvres applied in different experiments (1 and 2)…
Effects of a home-based rehabilitation program in obese type 2 diabetics.
2012
International audience; OBJECTIVE: To assess, in obese type 2 diabetics (T2D), the impact of a home-based effort training program and the barriers to physical activity (PA) practice. METHOD: Twenty-three obese T2D patients (52.7 ± 8.2 years, BMI = 38.5 ± 7.6 kg/m(2)) were randomized to either a control group (CG), or an intervention group (IG) performing home-based cyclergometer training during 3 months, 30 min/day, with a monthly-supervised session. The initial and final measurements included: maximal graded effort test on cyclergometer, 6-minute walk test (6MWT) and 200-meter fast walk test (200mFWT), quadriceps maximal isometric strength, blood tests and quality of life assessment (SF- 3…