Search results for "ELECTROMYOGRAPHY"
showing 10 items of 672 documents
Re-examination of training effects by electrostimulation in the human elbow musculoskeletal system.
2000
This study examines the effects of a 7 weeks sub-maximal training period of electrostimulation on the maximal isometric, concentric, eccentric voluntary torque and muscle contractile properties of the elbow flexor muscles of nine subjects. The daily program consisted of five series of six 6-s isometric actions (60 to 70% of maximal isometric voluntary action) at an elbow angle of 90 . After training the maximal voluntary isometric flexion torque increased significantly whereas the maximal voluntary isometric extension torque decreased significantly. Increases in isometric flexion torque were linked to an increase of the myoelectrical activity of the biceps brachii muscle. Under dynamic cond…
Continuous, bilateral Achilles' tendon vibration is not detrimental to human walk.
2001
Sensory feedback from the moving limbs contributes to the regulation of animal and human locomotion. However, the question of the specific role of the various modalities is still open. Further, functional loss of leg afferent fibres due to peripheral neuropathy does not always lead to major alteration in the gait pattern. In order to gain further insight on proprioceptive control of human gait, we applied vibratory tendon stimulation, known to recruit spindle primary afferent fibres, to both triceps surae muscles during normal floor walk. This procedure would disturb organisation and execution of walking, especially if spindles fire continuously and subjects are blindfolded. Vibration induc…
Plasma catecholamine responses and neural adaptation during short-term resistance training
2000
Low exercise-induced plasma adrenaline (A) responses have been reported in resistance-trained indi- viduals. In the study reported here, we investigated the interaction between strength gain and neural adaptation of the muscles, and the plasma A response in eight healthy men during a short-term resistance-training period. The subjects performed 5 resistance exercises (E1-E5), consisting of 6 sets of 12 bilateral leg exten- sions performed at a 50% load, and with 2 days rest in between. Average electromyographic (EMG) signal amplitude was recorded before and after the exercises, from the knee extensor muscles in isometric maximal voluntary contraction (MVC) as well as during the exercises (a…
Hormonal Responses to a Resistance Exercise Performed Under the Influence of Delayed Onset Muscle Soreness
2002
Hormonal responses to an unaccustomed knee-extension exercise (E1; 5 times 10 repetitions with 40% load of 1RM [1 repetition maximum] followed by 2 sets until exhaustion) were compared in 6 men with the corresponding responses to an identical exercise performed 2 days later under the influence of delayed onset muscle soreness (DOMS) (E2). Both exercises were performed with a variable-resistance machine causing exhaustion with significantly fewer repetitions than a normal constant-resistance knee-extension device does. The E1 induced DOMS as expected, but the 1RM, the total work done, and the repetition number and frequency were not different in the 2 exercises. In the 2 sets to failure, the…
Effects of oxygen fraction in inspired air on force production and electromyogram activity during ergometer rowing
1997
Six male rowers rowed maximally for 2500 m in ergometer tests during normoxia (fractional concentration of oxygen in inspired air, F IO2 0.209), in hyperoxia (F IO2 0.622) and in hypoxia (F IO2 0.158) in a randomized single-blind fashion. Oxygen consumption (V˙O2), force production of strokes as well as integrated electromyographs (iEMG) and mean power frequency (MPF) from seven muscles were measured in 500-m intervals. The iEMG signals from individual muscles were summed to represent overall electrical activity of these muscles (sum-iEMG). Maximal force of a stroke (F max) decreased from the 100% pre-exercise maximal value to 67 (SD 12)%, 63 (SD 15)% and 76 (SD 13)% (P<0.05 to normoxia, AN…
The Effects of a Prolonged Running Exercise on Strength Characteristics
2000
The aim of this study was to examine concentric, isometric, and eccentric strength reductions in the quadriceps muscle following a prolonged running exercise. Before and after a 2 h run (28.4+/-1.4 km) peak torque (PT) of the knee extensors at angular velocities of -120, -90, -60, 0, 60, 120, 180, 240 degrees x s(-1) using an isokinetic dynamometer, electromyographic (EMG) activity of the vastus lateralis (VL) and vastus medialis (VM) muscles and height of a counter movement jump were recorded in twelve well-trained triathletes. Counter movement jump performances decreased by 10% and PT values were all significantly lower (p < 0.01) at each angular velocity following the run. The torque los…
Neuromuscular efficiency of the triceps surae in induced and voluntary contractions: morning and evening evaluations.
2004
Variations in force and electromyographic (EMG) activities of skeletal muscles with the time-of-day have been previously described, but not for a postural muscle, submitted to daily postural and locomotor tasks. In this article, mechanical performances, EMGs, and the ratio between these parameters, i.e., the neuromuscular efficiency (NME), were measured on the triceps surae (TS) of eight subjects, two times each day, at 6:00 and 18:00 h. NME was evaluated under different experimental conditions (electrically induced contractions, reflex contractions, maximal and submaximal voluntary isometric contractions, and during a natural movement, a drop jump) to determine whether mechanisms, peripher…
Effect of time-of-day-specific strength training on maximum strength and EMG activity of the leg extensors in men.
2008
In this study, we examined the effects of time-of-day-specific strength training on maximum strength and electromyography (EMG) of the knee extensors in men. After a 10-week preparatory training period (training times 17:00-19:00 h), 27 participants were randomized into a morning (07:00-09:00 h, n = 14) and an evening group (17:00-19.00 h, n = 13). Both groups then underwent 10 weeks of time-of-day-specific training. A matched control group (n = 7) completed all testing but did not train. Unilateral isometric knee extension peak torque (MVC) and one-repetition maximum half-squat were assessed before and after the preparatory training and after the time-of-day-specific training at times that…
Effects of time-of-day on neuromuscular function in untrained men: Specific responses of high morning performers and high evening performers
2015
It has been clearly established that maximal force varies during the day in human muscles but the exact mechanisms behind the diurnal rhythms are still not fully clarified. Therefore, the aim of this study was to examine the diurnal rhythms in maximal isometric force production in a large group of participants and also by separating the high morning performance types (n = 8) and the high evening performance types (n = 19) from the neutral types (n = 45) based on their actual maximal isometric force levels. Measurements were performed in the morning (7:26 h ± 63 min) and in the evening (17:57 h ± 74 min) for maximal bilateral isometric leg press force (MVCLP) together with myoelectric activi…
Plantar Flexion Torque as a Function of Time of Day
2006
The possible peripheral and/or central origin in the mechanisms responsible for day-time fluctuation in maximal torque of the triceps surae muscle were investigated with a special emphasis on antagonist muscle coactivation. Eleven healthy male subjects (physical education students) took part in this investigation. The electromechanical properties of the plantar flexor muscles were recorded at two different times of day: between 06:00 h and 08:00 h in the morning and between 17:00 h and 19:00 h in the evening. To investigate peripheral mechanisms, the posterior tibial nerve was stimulated at rest, using percutaneous electrical stimuli, to evoke single twitch, double twitch, and maximal tetan…