Search results for "Motor"
showing 10 items of 3137 documents
Magnetic stimulation study in patients with myotonic dystrophy
1997
To further define motor nervous system alterations in myotonic dystrophy (MD), motor potentials to transcranial and cervical magnetic stimulation (MEPs) were recorded from the right abductor pollicis brevis muscle in 10 patients with MD and in 10 healthy controls. Cortical and cervical latencies, central motor conduction time (CMCT), stimulus threshold intensity and cortical MEP amplitudes expressed both as absolute values and as %M were analysed. MEP cervical latency, absolute or relative amplitude and excitability threshold did not significantly differ in patients and controls. The mean cortical motor latency and CMCT were significantly prolonged in MD patients with respect to normal subj…
Age and Grip Strength Predict Hand Dexterity in Adults.
2015
In the scientific literature, there is much evidence of a relationship between age and dexterity,\ud where increased age is related to slower, less nimble and less smooth, less coordinated\ud and less controlled performances. While some suggest that the relationship is a direct consequence\ud of reduced muscle strength associated to increased age, there is a lack of research\ud that has systematically investigated the relationships between age, strength and\ud hand dexterity. Therefore, the aim of this study was to examine the associations between\ud age, grip strength and dexterity. 107 adults (range 18-93 years) completed a series of hand\ud dexterity tasks (i.e. steadiness, line tracking…
Neuromuscular and physiological variables evolve independently when running immediately after cycling
2015
International audience; During the early period of running after cycling, EMG patterns of the leg are modified in only some highly trained triathletes. The majority of studies have analysed muscle EMG patterns at arbitrary, predetermined time points. The purpose of this study was to examine changes to EMG patterns of the lower limb at physiologically determined times during the cycle-run transition period to better investigate neuromuscular adaptations. Six highly trained triathletes completed a 10 min isolated run (IR), 30 min of rest, then a 20 min cycling procedure, before a 10 min transition run (C-R). Surface EMG activity of eight lower limb muscles was recorded, normalised and quantif…
Age dependent changes of distractibility and reorienting of attention revisited: an event-related potential study.
2012
Adults of three age groups (18-27, 39-45, and 59-66 years) performed an auditory duration discrimination task with short (200 ms) or long (400 ms) sinusoidal tones. Performance was highly accurate and reaction times were on the same level in all groups, indicating no differences in auditory duration processing. Task irrelevant rare changes of the frequency of the stimuli were introduced to check whether the subjects, firstly, were distracted by changes in the environment while focusing on the task relevant information (indicated by prolonged responses), and, secondly, could re-focus on the relevant task after distraction. The results show that a distraction effect is present in all groups. …
Age-related decreases in motor unit discharge rate and force control during isometric plantar flexion.
2012
Aging is related to multiple changes in muscle physiology and function. Previous findings concerning the effects of aging on motor unit discharge rate (DR) and fluctuations in DR and force are somewhat contradictory. Eight YOUNG and nine OLD physically active males performed isometric ramp (RECR) and isotonic (ISO) plantar flexions at 10 and 20% of surface EMG at MVC. Motor unit (MU) action potentials were recorded with intramuscular fine-wire electrodes and decomposed with custom build software "Daisy". DR was lower in OLD in RECR-10% (17.9%, p0.001), RECR-20% (15.8%, p0.05), ISO-10% (17.7%, p0.01) and ISO-20% (14%, n.s.). In YOUNG force fluctuations were smaller at ISO-10% (72.1%, p0.001)…
Effects of ageing on motor unit activation patterns and reflex sensitivity in dynamic movements.
2009
Both contraction type and ageing may cause changes in H-reflex excitability. H reflex is partly affected by presynaptic inhibition that may also be an important factor in the control of MU activation. The purpose of the study was to examine age related changes in H-reflex excitability and motor unit activation patterns in dynamic and in isometric contractions. Ten younger (YOUNG) and 13 elderly (OLD) males performed isometric (ISO), concentric (CON) and eccentric (ECC) plantarflexions with submaximal activation levels (20% and 40% of maximal soleus surface EMG). Intramuscular EMG data was analyzed utilizing an intramuscular spike amplitude frequency histogram method. Average H/M ratio was a…
Decline in motor prediction in elderly subjects: right versus left arm differences in mentally simulated motor actions.
2008
This study investigates the effects of age upon the temporal features of executed and imagined movements performed with the dominant (D; right) and nondominant (ND; left) arms. Thirty right-handed subjects were divided into two groups: (i) the young group (n=15; mean age: 22.5+/-2.5 years) and (ii) the elderly group (n=15; mean age: 70.2+/-2.2 years). The motor task, involving arm pointing movements among four pairs of targets (.5cm, 1cm, 1.5cm and 2cm), imposed strong spatiotemporal constraints. During overt performance, young and elderly subjects modulated movement duration according to the size of targets, despite the fact that movement speed decreased with age as well as in the left arm…
Mentally represented motor actions in normal aging: III. Electromyographic features of imagined arm movements.
2009
Abstract Motor imagery is a cognitive process during which subjects mentally simulate movements without actually performing them. Here, we investigated the temporal and electromyographic (EMG) features of imagined arm movements in healthy elderly adults. Twelve young (mean age: 24.0 ± 1.3 years) and 12 elderly (mean age: 67.0 ± 4.5 years) participants executed and mentally simulated, with their right and left arms and as fast and as accurately as possible, arm pointing movements between three targets located in the frontal plane. We used the mental chronometry paradigm as an indicator of the accuracy of the motor imagery process (i.e. isochrony between executed and imagined movements) and t…
Relation between muscle mass, motor units and type of training in master athletes.
2014
OBJECTIVE: The aim of this study was to measure the number of motor units and muscle mass in power-trained and endurance-trained master athletes compared with community-dwelling older adults. METHODS: Seventy-five master athletes (52 power- and 23 endurance-trained athletes) were recruited at the 2012 European Veteran Athletics Championships in Zittau (Germany). One hundred and forty-nine community-dwelling older adults served as controls. In all participants, the motor unit number index (MUNIX) in the hypothenar muscle and whole body muscle mass was determined by bioelectrical impedance analysis (BIA). RESULTS: In both male and female master athletes, there were significant negative correl…
Effect of caffeine on simulator flight performance in sleep-deprived military pilot students.
2007
Caffeine has been suggested to act as a countermeasure against fatigue in military operations. In this randomized, double-blind, placebo-controlled study, the effect of caffeine on simulator flight performance was examined in 13 military pilots during 37 hours of sleep deprivation. Each subject performed a flight mission in simulator four times. The subjects received either a placebo (six subjects) or 200 mg of caffeine (seven subjects) 1 hour before the simulated flights. A moderate 200 mg intake of caffeine was associated with higher axillary temperatures, but it did not affect subjectively assessed sleepiness. Flight performance was similar in both groups during the four rounds flown und…