Search results for "Myograph"

Evidence of a preprogrammed deactivation of the hamstring muscles for triggering rapid changes of posture in humans

1997

Normal subjects were asked to make rapid flexions of the legs from a stationary initial standing posture in a self-paced mode. Because this movement implicates a rapid change in posture, questions were asked about the type of central command which must include the rupture of the erect posture and the accomplishment of the goal directed movement. Movements of the different segments of the body were recorded and analyzed using the optoelectronic ELITE system. Electromyographic (EMG) activities of 8 muscles of the lower limb on one side were recorded, rectified and integrated. The time relationships of the different EMG signals (activation or deactivation) were analyzed with respect to selecte…

Biomechanical loading in the triple jump

2000

The triple jump is a demanding field event in which a jumper must tolerate extremely high impact forces while maintaining high horizontal speed. The present study was designed to clarify the mechanical loading characteristics and the role of neuromuscular function in the triple jump. Seven national triple jumpers (4 males, 3 females) volunteered to perform 3-6 jumps. The mean best performances were 14.32+/-0.45 m and 11.90+/-0.28 m for males and females, respectively. The three longest triple jumps for each jumper were selected for final analysis. The mean contact times were 0.139 s (hop), 0.157 s (step) and 0.177 s (jump). The largest ground reaction forces were observed in the step (15.2 …

Withdrawal reflex organisation to electrical stimulation of the dorsal foot in humans.

2001

The present study investigated excitatory reflex receptive fields for various muscle reflex responses and reflex mediated ankle joint movements using randomised electrical stimulation of the dorsal and plantar surface of the foot in 12 healthy subjects. Eleven electrodes (0.5-cm2 cathodes) were mounted on the dorsal side and three on the plantar side of the foot. A low (1.5 times pain threshold) and a high (2.3 times pain threshold) stimulus intensity were used to elicit the reflexes. EMG signals were recorded from tibialis anterior (TA), gastrocnemius medialis (GM), soleus (SO), biceps femoris (BF), and rectus femoris (RF) muscles together with the ankle movement measured by a goniometer. …

Modulation of intracortical inhibition induced by low- and high-frequency repetitive transcranial magnetic stimulation.

2001

We studied the changes of duration of subsequent silent periods (SPs) during repetitive magnetic stimulation (rTMS) trains of ten stimuli delivered at low (1 Hz) and high (7 Hz) frequencies. The effects at different intensities of stimulation (motor threshold, MT, 115% and 130% above the MT) were also evaluated. rTMS was performed in eight healthy subjects with a figure-of-eight coil placed over the hand motor area. The SP was recorded from abductor pollicis brevis (APB) muscle during a voluntary contraction of 30% of maximum effort. rTMS at 1-Hz frequency progressively decreased the duration of SP, whereas an alternating pattern of smaller and larger values was observed during trains at 7-…

Emotional communication in the context of joint attention for food stimuli: Effects on attentional and affective processing

2014

Guided by distinct theoretical frameworks (the embodiment theories, shared-signal hypothesis, and appraisal theories), we examined the effects of gaze direction and emotional expressions (joy, disgust, and neutral) of virtual characters on attention orienting and affective reactivity of participants while they were engaged in joint attention for food stimuli contrasted by preference (disliked, moderately liked, and liked). The participants were exposed to videos of avatars looking at food and displaying facial expressions with their gaze directed either toward the food only or toward the food and participants consecutively. We recorded eye-tracking responses, heart rate, facial electromyogr…

Human isometric force production and electromyogram activity of knee extensor muscles in water and on dry land.

1999

This study was designed to determine trial-to-trial and day-to-day reproducibility of isometric force and electromyogram activity (EMG) of the knee extensor muscles in water and on dry land as well as to make comparisons between the two training conditions in muscle activity and force production. A group of 20 healthy subjects (12 women and 8 men) were tested three times over 2 weeks. A measurement session consisted of recordings of maximal and submaximal isometric knee extension force with simultaneous recording of surface EMG from the vastus medialis, vastus lateralis and biceps femoris muscles. To ensure identical measurement conditions the same patient elevator chair was used in both th…

Electromechanical behaviour of human muscles in vertical jumps

1982

The relationships of muscle structure to the potentiation of myoelectrical activity and to the use of prestretching in five lower limb muscles were studied in different vertical jumping conditions. The subjects for the study were six male students, divided according to the muscle fiber distribution in m. vastus lateralis into “fast” and “slow” groups. The subjects performed vertical jumps (1) from a static squatting position (SJ), (2) with a preliminary counter movement (CMJ) and (3) after dropping (DJ) from five different heights. Myoelectrical (EMG) activity was recorded from mm. gluteus maximus, vastus lateralis, vastus medialis, rectus femoris and gastrocnemius in each jumping condition…

Effects of a 21 days space flight on the mechanical performance and the EMG power spectrum of the leg muscles

2002

Preparedness for landing after a self-initiated fall.

2012

A startling auditory stimulus (SAS) causes a faster execution of voluntary actions when applied together with the imperative signal in reaction time tasks (the StartReact effect). However, speeding up reaction time may not be the best strategy in all tasks. After a self-initiated fall, the program for landing has to be time-locked to foot contact to avoid damage, and therefore advanced execution of the program would not be convenient. We examined the effects of SAS on the landing motor program in 8 healthy subjects that were requested to let themselves fall from platforms either 50 or 80 cm high at the perception of a visual imperative signal and land on specific targets. In trials at rand…

Abnormal facilitatory mechanisms in motor cortex of migraine with aura

2010

Experimental evidence suggests impairment of inhibitory intracortical circuits in migraine, while not much is known about activity of facilitatory intracortical circuits. In the present work we evaluated the effects of high frequency-repetitive transcranial magnetic stimulation (hf-rTMS) on the activity of facilitatory circuits of motor cortex in 18 patients affected by migraine with aura and 18 healthy subjects. Trains of 10 stimuli were applied to the motor cortex at 5-Hz frequency with recording of the EMG traces from the contralateral abductor pollicis brevis muscle (APB). Two intensities of stimulation (110% and 130% of resting motor threshold) were used in order to explore whether mot…