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- Activation timing of soleus and tibialis anterior muscles during sit-to-stand and stand to sit in post-stroke vs healthy subjectsPublication . Augusta Silva; Santos, Rubim; Pinheiro De Sousa, Andreia Sofia; Pinheiro, Ana Rita; Ferraz, Joana; Tavares, João Manuel; Sousa, FilipaSit-to-stand (SitTS) and stand-to-sit (StandTS) are very important functional tasks that become compromised in stroke patients. As in other voluntary movements, they require an adequate postural control (PC) involving the generation of anticipatory postural adjustments (APAs). In order to give clues for more efficient and directed rehabilitation programs, a deeper knowledge about APAs during challenging and daily life movements is essential. To analyze the activation timing of tibialis anterior (TA) and soleus (SOL) muscles during SitTS and StandTS in healthy subjects and in post-stroke patients. Methods: Two groups participated in this study: one composed by ten healthy subjects and the other by ten subjects with history of stroke and increased H-reflex. Electromyographic activity (EMGa) of SOL and TA was analyzed during SitTS and StandTS in the ipsilateral (IPSI) and the contralateral (CONTRA) limb to the side lesion in stroke subjects, and in one limb in the healthy subjects. A force plate was used to identify the movement onset. In both sequences, in the stroke group SOL activation timing occurred prior to movement onset, contrary to the pattern observed in the healthy subjects. Statistical significant differences were found in SOL activation timings between each lower limbs of the stroke and healthy groups, but no significant differences were found between the IPSI and the CONTRA limb. The TA activation timing seems to be delayed in the CONTRA limb when compared to the healthy subjects and showed also a better organization of TA timing activation in StandTS when compared to SitTS. Compared to healthy subjects, APAs seems to be altered in both limbs of the post-stroke subjects, with the SOL activation timing being anticipated in both SitTS and StandTS.
- Acupuncture effect on reaction-time changes in Parkinson’s disease patients—Case study seriesPublication . Pereira, Catarina Ramos; Greten, Henry J.; Santos, Rubim; Reis, Ana Mafalda; Ramos, Bruno; Santos, Maria João; Machado, Jorge; Criado, Maria BegoñaParkinson’s Disease (PD) is a progressive neurodegenerative condition associated with deficit in reaction time which can lead to falls, resulting in limited independence, diminished quality of life, heightened rates of institutionalization and increased healthcare costs. We aimed to examine the effects of an acupuncture protocol in motor time response after an auditory stimulus. Methods: This study employed a case series design. Reaction time to exposed rhythmic and random auditory stimuli outcomes were evaluated at six different moments over a month-long acupuncture treatment protocol using the MP 36 system from Biopac Systems. Results: We observed a tendency to have more pronounced improvements in the time response in the more affected side of the body compared with the contralateral one. Patients tended to show better values of response to random auditory stimuli compared to rhythmic auditory ones. We also observed a tendency to obtain better results when considering the accumulative effects of the acupuncture protocol. Conclusions: Our findings indicated a possible role of reaction time as a sensitive and useful tool for motor function assessment in PD patients. Also, from our results, we concluded that the acupuncture protocol used may lead to an improvement in efficacy of motor response after aleatory and rhythmic stimulus; we also found a tendency for a higher efficacy of acupuncture in random stimuli responses in the first stages of the disease. However, further in-depth research, including a statistical evaluation with a larger participant pool, is necessary to validate and confirm these promising results.
- Acute effects of physical exercise with microcurrent in the adipose tissue of the abdominal region: A randomized controlled trialPublication . Noites, Andreia; Moreira, Anabela; Melo, Cristina; Faria, Miriam; Vilarinho, Rui; Freitas, Carla; Monteiro, Pedro; Carvalho, Paulo; Adubeiro, Nuno; Sousa, Maria; Santos, Rubim; Nogueira, LuisaIncreased abdominal fat and sedentary lifestyles contribute to cardiovascular disease risk. Low-intensity electrical current (microcurrent) on the abdominal region, associated with physical exercise, appears to be an innovative method to increase the lipolytic rate of abdominal adipocytes, in order to reduce abdominal fat. This study aimed to analyze the acute effects of microcurrent associated with an aerobic exercise program in healthy subjects in lipolysis. A double-blinded, randomized controlled trial was developed and conducted in a higher education school. Eighty-three healthy subjects, aged between 18 and 30 years old and with a 18.5 to 29.9 kg/m2 body mass index were randomly assigned either to an experimental or to a placebo group. Subjects received a trans-abdominal microcurrent stimulation for 40 min with (experimental group) or without (placebo group) electrical current, followed by a single aerobic exercise session (60 min at 45–55% VO2max intensity). Lipolytic activity (serum glycerol), abdominal fat (waist circumference, abdominal skinfold, ultrasonography), and serum lipid profile (serum triglyceride, total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol) were evaluated in all subjects. Physical activity (International Physical Activity Questionnaire) and dietary intake (food-frequency questionnaire) questionnaires were applied. After the intervention, lipolytic rate was significantly higher (p = 0.003) in the experimental group (mean = 0.15) than in the placebo group (mean = 0.09). Glycerol results showed a statistically significant increase between baseline and after the intervention for both experimental group (p = 0.001) and the placebo group (p = 0.001). Combined use of microcurrent and physical aerobic exercise had an acute effect enhancing lipolytic rate comparing to exercise alone, in young healthy subjects.
- An all-digital coincidence-selection and coincidence-trigger generation for a small animal RPC-PET cameraPublication . Clemêncio, Filomena; Loureiro, Custodio F. M.; Landeck, JorgeThe time resolution for gamma photon pairs of a detector based on resistive plate chamber technology is close to 300 ps FWHM. This allows a tight time window for coincidence detection, reducing the number of random coincidences observed and the overall noise of the acquired image. We implemented, inside a Xilinx Virtex-5 field programmable gate array, a fully programmable coincidence-trigger system with sub-nanosecond resolution and low latency for a small animal RPC-PET camera being built. An automatic procedure to construct a histogram of coincidences was implemented that helps characterizing the camera and allows compensating for different delays in the time channels. The time window for coincidences can then be placed at the optimal position helping rejecting coincidences from undesired sources.
- An easy procedure for calibrating data acquisition systems using interleavingPublication . Clemêncio, Filomena; Loureiro, Custódio F. M.; Correia, Carlos M. B. A.Interleaving data acquisition channels is a well-known and interesting technique to achieve higher acquisition rates. However, to obtain the expected benefits, a careful look at the interleaving technique and to mismatches that can lead to unwanted harmonic distortion and noise is essential. In this paper we discuss the methods used to interleave existing high-speed, 250 MSPS 8-bit acquisition channels, and the results obtained. The methods presented allowed a good relative channel calibration in amplitude (amplitude mismatch under 0.1 lsb) and in time (time mismatch between acquisition channels in the ps range, under the specified maximum jitter for the ADC used). A dynamic, by software, amplitude level signal-dependent adjustment procedure is also suggested for signals with rich frequency content that can substantially improve the quality of the acquired signal when using interleaved channels. The techniques presented provide good results even in the presence of noise.
- Analysis of ground reaction force and electromyographic activity of the gastrocnemius muscle during double supportPublication . Sousa, Andreia S. P.; Santos, Rubim; Oliveira, Francisco; Carvalho, Paulo; Tavares, João ManuelPurpose: Mechanisms associated with energy expenditure during gait have been extensively researched and studied. According to the double-inverted pendulum model energy expenditure is higher during double support, as lower limbs need to work to redirect the centre of mass velocity. This study looks into how the ground reaction force (GRF) of one limb affects the muscle activity required by the medial gastrocnemius (MG) of the contralateral limb during step-to-step transition. Methods: Thirty-five subjects were monitored as to the MG electromyographic activity (EMGa) of one limb and the GRF of the contralateral limb during double support. Results: After determination of the Pearson correlation coefficient (r), a moderate correlation was observed between the MG EMGa of the dominant leg and the vertical (Fz) and anteroposterior (Fy) components of GRF of the non-dominant leg (r=0.797, p<0.0001; r=-0.807, p<0.0001) and a weak and moderate correlation was observed between the MG EMGa of the non-dominant leg and the Fz and Fy of the dominant leg, respectively (r=0.442, p=0.018; r=-0.684 p<0.0001). Conclusions: The results obtained suggest that during double support, GRF is associated with the EMGa of the contralateral MG and that there is an increased dependence between the GRF of the non-dominant leg and the EMGa of the dominant MG.
- Ankle dynamic in stroke patients: agonist vs. antagonist muscle relationsPublication . Silva, Augusta; Sousa, Andreia S. P.; Tavares, João Manuel; Tinoco, Ana; Santos, Rubim; Sousa, FilipaAtypical ankle patterns of muscle activity during gait are commonly reported in patients with stroke. These findings can be due to changes between tibialis anterior (TA) and soleus (SOL) coactivation mechanisms. To compare the electromyographic activity (EMGa) of SOL and TA muscles and antagonist coactivation (C) level in the contralateral (CONTRA) and ipsilateral (IPSI) limbs to the side of the stroke lesion during stance phase of the gait cycle. Twelve subjects with a stroke episode participated in this study. The electromyographic signal of TA and SOL and ground reaction forces were acquired while subjects walked at their self-selected speed. Values of ground reaction forces were used to divide the stance phase of gait into initial contact, midstance and terminal stance. In each subphase the magnitude of TA and SOL was calculated as well as the level of the antagonist C. Although no statistical differences were found, mean values of SOL EMGa were lower in the IPSI in all stance phases in relation to the CONTRA limb, and the opposite was observed in the TA EMGa. Moreover, higher mean levels of antagonist C were only found during initial contact sub-phase in CONTRA limb and in the other sub-phases in the IPSI limb. Besides, statistical differences were observed only during midstance. Conclusion: In stroke subjects the antagonist C level during midstance of gait my reflected the dysfunction of the neuronal system over the IPSI limb.
- Ankle intrinsic stiffness in subcortical poststroke subjectsPublication . Pinheiro De Sousa, Andreia Sofia; Santos, Rubim; Silva, AugustaThe authors' purpose was to evaluate bilateral ankle intrinsic stiffness in subcortical poststroke subjects. Ten subcortical poststroke subjects and 10 healthy controls participated in this study. The ankle passive stiffness at 3 different speeds and the electromyographic activity of the soleus, the gastrocnemius, and the tibialis anterior muscles of poststroke contralesional (CONTRA) and ipsilesional (IPSI) limbs and of one limb of healthy subjects were assessed. Ankle electromyographic activity was collected to ensure that reflexive or voluntary muscle activity was not being elicited during the passive movements. A significant interaction was observed between the effects of the limb (IPSI vs. CONTRA vs. control) and ankle position, F(4, 28) = 3.285, p = .025, and between the effects of the limb and the velocity of stretch, F(2, 14) = 4.209, p = .037. While increased intrinsic stiffness was observed in the CONTRA limb of poststroke subjects at ankle neutral position when the passive stretch was applied with a velocity of 1°/s (p = .021), the IPSI limb of poststroke subjects presented increased stiffness at 20º of plantar flexion when the stretch was applied with a velocity of 5°/s (p = .009) when compared to healthy group. Subcortical poststroke subjects present increased intrinsic stiffness in both the CONTRA and IPSI limbs in specific ankle amplitudes.
- Antagonist coactivation of muscles of ankle and thigh in post-stroke vs. healthy subjects during sit-to-stand taskPublication . Pinho, Liliana; Sousa, Andreia S. P.; Silva, Cláudia; Cunha, Christine; Santos, Rubim; Tavares, João Manuel R. S.; Pereira, Soraia; Pinheiro, Ana Rita; Félix, José; Pinho, Francisco; Sousa, Filipa; Silva, AugustaThis study aims to analyse the coactivation of antagonist muscles of the thigh and ankle during the sit-to-stand task in post-stroke subjects, specifically during forward and antigravity sub-phases. A group of 18 healthy subjects and another with 18 subjects with a history of stroke participated voluntarily in this study. Bilateral surface electromyography (EMGs) of the soleus, gastrocnemius medialis, tibialis anterior, rectus femoris and biceps femoris muscles were collected synchronously with ground reaction forces (GRF) during the sit-to-stand task. The magnitude of electromyographic (EMG) activity was analysed during forward translation and antigravity sub-phases which were determined through GRF signals. The coactivation was calculated to quantify the degree of antagonist coactivation according to the role of the muscles during the task. Statistically significant values were found between antagonist coactivation on both sub-phases of the sit-to-stand task when comparing healthy and post-stroke subjects (healthy with ipsilesional (IPSI); healthy with contralesional (CONTRA); and healthy with IPSI and with CONTRA limbs) in all muscle pairs analysed (p < 0.01), except on thigh muscles (p > 0.05), in the antigravity sub-phase. When comparing IPSI with CONTRA sides in post-stroke subjects, no statistically significant differences were found. Increased values of antagonist coactivation were observed in post-stroke subjects compared to healthy subjects (both IPSI and CONTRA limb) in the two sub-phases analysed. The forward sub-phase CONTRA limb showed higher antagonist coactivation compared to IPSI, while in the antigravity sub-phase, IPSI antagonist coactivation was higher than in the CONTRA. In conclusion, post-stroke subjects presented an antagonist coactivation more dysfunctional at the ankle joint muscles compared to the thigh segment. So, it seems that the distal segment could express more accurately the central nervous system dysfunction in post-stroke subjects, despite the need for further studies to achieve a better spatiotemporal understanding of the variability on coactivation levels.
- Anticipatory postural adjustments during sitting reach movement in post-stroke subjectsPublication . Pereira, Soraia; Silva, Cláudia; Ferreira, Sílvia; Silva, Cláudia; Oliveira, Nuno; Santos, Rubim; Vilas Boas, João; Correia, Miguel V.The study assessed the effect of velocity of arm movement on the generation of APAs in the contralateral and ipsilateral muscles of individuals with stroke in the sitting position. In the sitting position, 10 healthy and 8 post-stroke subjects reached for an object placed at the scapular plane and mid-sternum height at self-selected and fast velocities. Electromyography was recorded from the anterior deltoid (AD), upper (UT) and lower trapezius (LT), and latissimus dorsi (LD). Kinematic analysis was used to assess peak velocity and trunk displacement. Post-stroke subjects presented a delay of APAs on both sides of the body compared to healthy subjects. Differences were found between the timing of APAs on the ipsilateral and contralateral LD and LT in both movement speeds and in the ipsilateral UT during movement of the non-affected arm at a self-selected velocity. A delay in the contralateral LD in the reaching movement with the non-affected arm at fast velocity was also observed. Trunk displacement was greater in post-stroke subjects. In the sitting position, APAs were delayed in both fast and self-selected movements on both sides in post-stroke subjects, which also presented a higher trunk displacement.