1,721,388 research outputs found
Shift of activity from slow to fast muscle during voluntary lengthening contractions of the triceps surae muscles in humans
No full text1. Raw or rectified and integrated electromyograms (integrated EMGs) of the leg muscles were recorded during (a) isotonic ramp shortening or lengthening contractions consisting of foot plantar flexions against a constant load, or dorsal flexions accomplished by braking the load and yielding to it, respectively, and (b) isometric increasing or decreasing plantar torques accomplished by graded contractions or relaxations of the triceps muscles. 2. During plantar flexions or increasing torques, the EMG of soleus, gastrocnemius lateralis, medialis, and peroneus increased in parallel. During decreasing torques, motor unit derecruitment took place gradually and simultaneously. The tibialis anterior was silent. During dorsal flexions, one of two characteristic patterns was observed in different subjects: (a) soleus was abruptly derecruited at the beginning of the task, while gastrocnemius lateralis (or medialis) exhibited a large recruitment lasting throughout the lengthening contraction; (b) soleus remained active during the task, showing large motor unit potentials, while the gastrocnemius lateralis recruitment was of a lesser extent than in (a). Peroneus derecruitment was gradual and tibialis anterior activity was absent in both cases. 3. The EMG patterns observed during plantar flexions or in increasing and decreasing torques, and the two patterns observed during shortening or lengthening contractions, were closely reproduced during sinusoidal oscillations of the foot or in isometric contractions and relaxations. 4. When recruitment of the gastrocnemius lateralis was present during dorsal flexion, the slope of its integrated EMG envelope was steeper, the higher the velocity of lengthening contraction. The most rapid and the slowest tasks, however, did not require its activation. Gastrocnemius lateralis integrated EMGs of an amplitude similar to those occurring during lengthening contractions were observed only during ballistic plantar flexions. 5. The two patterns of triceps activation occurring during lengthening contraction could be traced to different mechanical characteristics of the soleus muscles, the gastrocnemius lateralis being activated preferentially in subjects with long soleus half-relaxation times, and the soleus in subjects with short soleus half-relaxation times. 6. The soleus and gastrocnemius lateralis H reflexes were tested during shortening and lengthening contractions
Vision does not necessarily stabilize the head in space during continuous postural perturbations
No full textVision favors head stabilization in space during perturbations of standing balance. This is particularly obvious under conditions of continuous predictable perturbations as during sinusoidal antero-posterior (A-P) translations of the supporting platform. We tested here the hypothesis that under this condition the head can instead undergo large A-P oscillations, when a precision visual task is concurrently performed. We compared the head oscillations across four conditions while standing on a continuously translating platform. Eyes open (EO, no visual task), EO while reading a text fixed to the moving platform (EO-TP), EO while reading a text fixed to earth-ground (EO-TG), eyes-closed (EC). The platform translated at 0.2 and 0.6 Hz. Participants were young adult subjects, who received no particular instruction except reading the text aloud when required. Markers fixed on head, platform and text-sheet were captured by an optoelectronic device. We found that head oscillations were larger with EC than under all EO conditions. The oscillations were the least with EO and EO-TG, and intermediate with EO-TP. This was true under both low and high translation frequency, in spite of broadly smaller head oscillations at high frequency, common to all visual conditions. The distance between the head and the text was quite constant with EO-TP but fluctuated with EO-TG. The basic whole-body coordination features were moderately similar under all conditions, as assessed by the head-platform correlation coefficients and time lags. It appears that vision does not produce head stabilization in space when a concurrent visual task requiring focusing on a reading-text moving with the platform is performed. Contrary to traditional views centered on the stabilizing effect of vision under both static and dynamic conditions, the results show that head stabilization, normally ensuring a reference for inertial guidance for body balance, can be revoked by the CNS to allow performance of a non-postural task. This novel paradigm can shift long-standing views on the effect of vision on equilibrium control and be considered a potential exercise treatment for enhancing the multisensory integration process in people with balance problems
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Post-traumatic seizures and antiepileptic therapy as predictors of the functional outcome in patients with traumatic brain injury
No full textPost-traumatic seizures (PTS) are a common and debilitating complication of traumatic brain injury (TBI) and could have a harmful impact on the progress of patient rehabilitation. To assess the effect of PTS and relative therapy on outcome in the initial phase after TBI, during the rehabilitation process when neuroplasticity is at its highest, we retrospectively examined the clinical data of 341 adult patients undergoing rehabilitation for at least 6 months post-TBI in our neurorehabilitation unit between 2008 and 2019. We correlated through logistic regression the occurrence of seizures and use of anti-seizure medication (ASM) with neurological and functional outcomes, respectively assessed with the Glasgow Coma Scale (GCS) and the Functional Independence Measure (FIM). PTS were documented in 19.4% of patients: early PTS (EPTS) in 7.0%; late PTS (LPTS) in 9.4%; both types in 3.0%. Patients who developed EPTS had an increased risk of developing LPTS (OR = 3.90, CI 95% 1.58–9.63, p = 0.003). Patients with LPTS had a significantly higher risk of worse neurological (p < 0.0001) and rehabilitation (p < 0.05) outcome. Overall, 38.7% of patients underwent therapy with ASM; prophylactic therapy was prescribed in 24.0% of patients, of whom 14.6% subsequently developed seizures. Mortality was associated with a lower FIM and GCS score on admission but not significantly with PTS. The use of ASM was associated with a worse rehabilitation outcome, independently of the onset of epilepsy during treatment. LPTS appear to exert a negative impact on rehabilitation outcome and their occurrence is not reduced by prophylactic therapy, whereas EPTS do not influence outcome. Our findings caution against the generic use of prophylactic therapy to prevent post-traumatic epilepsy in patients with TBI
Human balance in response to continuous, predictable translations of the support base: Integration of sensory information, adaptation to perturbations, and the effect of age, neuropathy and Parkinson's disease
No full textThis short narrative review article moves from early papers that described the behaviour of healthy subjects balancing on a motorized platform continuously translating in the antero-posterior direction. Research from the laboratories of two of the authors and related investigations on dynamic balancing behaviour are briefly summarized. More recent findings challenging time-honoured views are considered, such as the statement that vision plays a head-in-space stabilizing role. The time interval to integrate vision or its withdrawal in the balancing pattern is mentioned as well. Similarities and differences between ageing subjects and patients with peripheral or central disorders are concisely reported. The muscle activities recorded during the translation cycles suggest that vision and amplitude changes of the anticipatory postural activities play a predominant role in controlling dynamic balance during prolonged administration of the predictable perturbation. The potential of this paradigm for rehabilitation of balance problems is discussed
Caratteristiche quali-quantitative del latte
No full textSelezione molecolare per le caratteristiche quali-quantitative
del latt
Cognitive performance during gait is worsened by overground but enhanced by treadmill walking
No full textPURPOSE: Walking is an attention-demanding task that affects and is affected by cognitive performance. Since treadmill walking (TW) assists gait automaticity, we have hypothesized that TW affects cognitive performance to a smaller extent than overground walking (OW). METHODS: Thirty young adults were recruited. Each subject walked overground over a 20-meter straight hallway at three different speeds (slow, normal and fast). Each task was repeated 3 times under Single Task (OW-ST) and Dual Task (OW-DT) condition, in a randomized sequence. DT was a serial subtraction by 7 starting from a different number (> 100) in each trial. Afterwards, each subject walked on the treadmill at the same three speeds as during OW-ST, while performing the dual task (TW-DT). The correct cognitive response (CCR), calculated from the number of correct responses and mistakes, was compared between rest, OW-DT and TW-DT. Dual-task cost (DTC) was calculated for speed and for CCR. RESULTS: Backward counting diminished normal and fast OW-DT speed by about 15 %. Slow OW-DT speed was not significantly reduced. In turn, OW affected the cognitive performance. DTC for speed during OW-DT increased during normal and fast speed. CCR significantly decreased, more at slower OW-DT speed. Conversely, CCR was not worsened by TW-DT. CCR did not decline at slow TW-DT speed and improved significantly from slow and normal to fast speeds. DTC for CCR resulted smaller in TW-DT than OW-DT. CONCLUSIONS: Decline in the cognitive performance during OW-DT is more prominent at slow speed, in keeping with higher demand of attentional resources for this unusual locomotor behaviour. Conversely, motorized TW improves the cognitive performance likely because it reduces the attentional cost of walking. Gait training by TW might improve automaticity in patients with movement disorders
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