The rate of force development (RFD), is seen as a determining characteristic in fast actions present in basketball. However, we observed different relationships between RFD and maximum strength, as well as different relationships between RFD and neuromuscular variables according to the evaluated population. The aim of the present study is to evaluate the degree of determination of maximum strength (Tmax) and neuromuscular recruitment variables (RMS), Absolute Energy (AE) and the motor units firing frequencies (MPF) in rate of force development (RFD) for basketball athletes. Nine basketball athletes from the same team (mean ± SD; age: 20.8 ± 2.08 years; body mass: 84.33 ± 8.80kg; height: 1.86 ± 0.095 meters; practice time: 11.67 ± 1.65 years) were evaluated through maximum isometric contraction with highest value of maximum force among 3 attempts. The RFD were evaluated and correlated with the RMS and AE values and the MPF values of the electromyographic signal at instants 0-50; 50-100, 100-150 and 150-200 milliseconds. The results show a reduction in RFD and MPF over the evaluated time windows and also a correlation between MPF and TDF in the 0-50ms time window (R[2][1] 0.67 p <0.05). The results show no relationship between RFD and RMS and AE, in addition to these variables not showing significant reductions in the evaluated time windows. The levels of RFD show to be more related to the firing frequency of the motor units than the maximum force and the level of recruitment of the motor units.### Competing Interest StatementNO authors have competing interests Enter: The authors have declared that no competing interests exist. [1]: #ref-2

Training in team sports such as soccer requires advanced technical and tactical skills for effective decision-making, particularly when executing a shot. This study validates an innovative instrument, a training platform (TP), designed to measure and enhance decision-making in dual-task scenarios. The TP aims to improve visual–motor reactions in multitask environments that simulate real game conditions. Equipped with an LED panel, main circuitry, ball sensor, and targets, the TP challenges players to kick the ball in response to the illumination of the final LED array on the panel while hitting a designated target. The study evaluated three parameters: reaction time (RT), ball speed (BS) and accuracy. To validate the TP against a gold standard (GS), we conducted correlation analyses. The results exhibited very strong correlations for both RT (r = 0.997) and BS (r = 0.994). The mean differences between TP and GS measurements were 13 ± 15 ms for RT and 0.1 ± 0.5 km/h for BS. Bland–Altman plots revealed trend lines obtained by a simple linear regression of r = −0.507, p = 0.307 for RT and r = 0.134, p = 0.077 for BS. The TP effectively simulates game scenarios, offering advantages such as low-cost components, installation flexibility, test variability, instant feedback, and integration of physical and cognitive components of sports performance.

Disturbances in balance control lead to movement impairment and severe discomfort, dizziness, vertigo and may also lead to serious accidents. It is important to monitor the level of balance in order to determine the risk of a fall and to evaluate progress during treatment. Some solutions exist, but they are generally restricted to indoor environments. We propose and evaluate a system, based on accelerometers and support vector machines, that indicates the user’s postural balance variation which can be used in indoor and outdoor environments. For the training phase of the system, we used the accelerometer signals acquired from a single subject under monitored conditions of balance and intentional imbalance, and used the scores provided by the SWAY®software for establishing the reference target values. Based on these targets, we trained a support vector machine to classify the signal into n levels of balance and later evaluated the performance using cross validation by random resampling. We also developed a support vector machine approach for estimating the center of pressure, by using as reference targets the results from a force platform. For validation, we performed experiments with a subject who was performing determined movements. Later other experiments were executed, so the different centers of pressure could be computed by our system and compared to the results from the force platform. We also performed tests with a dummy and a John Doe doll, in order to observe the system’s behavior in the presence of a sudden drop or a lack of balance. The results show that the system can classify the acquired signals into two to seven levels of balance, with significant accuracy, and was also able to infer the centroid of each center of pressure region with an error lower than 0.9 cm. The tests performed with the dolls show that the system is able to distinguish between the conditions of a sudden drop and of a recovery of balance after losing one’s balance. The results suggest that the system can be used to detect variations in balance and, therefore, to indicate the risk of a fall even in outdoor environments.

The present work investigates the temporal analysis window length and the amount of overlap between successive windows in muscular fatigue estimation using the Weighted-Cumulated Methodology. The theoretical basis of the methodology is resumed, followed by a description of the weighted cumulated root mean square, weighted cumulated median frequency and weighted cumulated Fourier estimators. Analyses are made using real surface electromyography signals from isometric fatiguing contractions of the biceps bacchii of five healthy subjects. The sensibility to muscular fatigue manifestations of the three cumulated normalized parameters is evaluated using different combinations of window sizes and window overlaps. The results show a considerable influence of the window size in the values of sensibility to muscular fatigue of the cumulated normalized estimators. On the other hand, varying the amount of windows overlap is shown to have basically no effect on the sensibility descriptors.

Background: Myofascial release (MR) has been widely used in sports and clinical environment. There are studies that have already evaluated the effect of MR on postural control, however, the data found are inconclusive. Objectives: Investigate the effect of MR on ankle plantar flexor muscles over static postural balance. Method: Sixty-five young men were randomized allocated into one of three groups: 1) MR group (n = 25, Myofascial Release); 2) Sham (n = 25, fake intervention); or 3) Control group (n = 15). Both MR and Sham techniques were applied during 5 min in the ankle flexors of each leg. The bipodal static postural balance test was performed before and 2 min post each intervention on a force plate with eyes closed during the test. All subjects performed 3 sets of 30-s with 1 min of rest. Mean values to the center of pressure velocity (COPvel) was used for analysis. Results: The bipodal balance test showed that there was no significant difference between groups (p > 0.05), but there was a significant time effect (p < 0.05). A significant decrease (p < 0.05) in post-test COPvel (cm.s(-1)) values (sham 4.9 +/- 1.2; MR 4.5 +/- 0.6; CON 4.22 +/- 0.8) was found when compared to values of pre-test (sham 5.3 +/- 1.0; MR 5.0 +/- 0.8; CON 4.94 +/- 1.3) for all groups. Conclusions: The results demonstrated that MR performed on ankle flexors did not affect static postural balance in young man. This study is a clinical trial (Register Number: RBR-48k5jm). (c) 2021 Published by Elsevier Ltd.

Background: The blood pressure responses to baroreflex perturbations can be assessed only using the variable-pressure neck chamber technique. However, the application of this approach in hospital environments is limited owing to the loud noise emitted during its operation. This study was aimed at developing a noiseless neck suction chamber device (NCD) that could stimulate the baroreceptors located in the carotid sinus in humans.Methods: A non-invasive device was developed to pressurize the carotid arteries externally. A microcontroller with a computer interface and neck chamber (3D-printed) was used. The anatomical neck chamber was fitted on six healthy, young, asymptomatic participants (five men; 32 ± 6 year), who were normotensive, nonsmoking, in sinus rhythm, free of known cardiovascular or metabolic diseases, and not consuming any acute or chronic medications. A suction of −60 mmHg was applied for 5 s, and the corresponding data were recorded. Before each study visit, the participants were instructed to abstain from caffeine, alcohol, and strenuous exercise for 12–24 h.Results: In all the trials, a significant reflex bradycardia (−10 ± 2 bpm) and depressor response (−15 ± 4 mmHg) to neck suction were observed, consistent with the results in the literature. The neck chamber device operated noiselessly [sound pressure level (SPL) of 34.3 dB] compared to a regular vacuum-cleaner-based system (74.6 dB).Conclusion: Using the proposed approach, consistent blood pressure and heart rate responses to carotid baroreflex hypertensive stimuli could be recorded, as in previous studies conducted using neck collar devices. Furthermore, the neck chamber device operated noiselessly and can thus be applied in hospital environments.

Sickle cell anemia is a chronic disease that can severely affect the ability to process information quickly. The aim of this study was to evaluate the reaction time in children with sickle cell anemia using simple reaction time and choice reaction time tests. A cross-sectional study was performed at the Children's Hospital of Brasilia, with patients from the hematology outpatient clinic. The experimental group was composed of 24 sickle cell children and the control group of 22 children not affected by sickle cell anemia. The simple reaction time and choice reaction time were evaluated using equipment developed for this purpose. The results showed a significant deficit in the choice reaction time of children with sickle cell anemia (p= 0.000161). In simple reaction time, the experimental group showed less attention, committing a higher proportion of errors by omission when compared to the control group (p= 0.00678). The lower rate of success in simple reaction time and choice reaction time tests in children with sickle cell anemia may be related to the high incidence of silent cerebral infarction in this population. Another fact that may be associated with high reaction time in patients with sickle cell anemia is the lack of experience and opportunities for motor activities throughout childhood due to the pathology. KEYWORDS: chronic disease; hemoglobin, sickle; child development; psychomotor performance; brain injuries.

Background/objective: Roller massage has become a popular intervention in sports settings in order to treat muscle soreness and stiffness, as well as improving post-exercise recovery, although there is limited evidence for these assumptions. Therefore, the purpose of this study was to evaluate the effects of a single session of roller massage, applied with a controlled force after an exercise-induced muscle damage protocol, on muscle recovery. Methods: A randomized controlled study was performed using a repeated-measures design. Thirty-six young men completed four sets of six eccentric actions of elbow flexors at 90°/s with a 90s rest interval between sets. Participants were randomly assigned into one of three groups: 1) Roller massage (n = 12), 2) Sham (n = 12), and 3) Control (n = 12). Maximal isometric voluntary contraction (MIVC), delayed-onset muscle soreness (DOMS), range of motion (ROM), and muscle thickness were measured at baseline, and at 24, 48, and 72 h post exercise. Results: There was no significant group by time interaction for MIVC (p = 0.090) and ROM (p = 0.416). Also, although there was a significant group by time interaction for muscle thickness (p = 0.028), post hoc test did not find significant difference between groups (p > 0.05). DOMS was recovered at 72 h for roller massage (p < 0.001) and control (p < 0.001) groups, while the Sham group did not recover from DOMS across 72 h (p < 0.001). There was also no significant difference between groups in DOMS at any time (p > 0.05). Conclusions: A single session of roller massage applied on elbow flexors had no effect on recovery of MIVC, muscle swelling, ROM and DOMS.

IntroductionCerebral blood flow is tightly coupled with local neuronal activation and metabolism (i.e., neurovascular coupling; NVC). Attenuated NVC has been identified in several chronic diseases, including hypertension, but the underlying mechanism(s) remains unknown. Raised peripheral sympathetic vasoconstrictor activity can play a malevolent role in the pathology of hypertension and might also contribute to the blunted NVC as cerebral arteries are autonomic innervated. However, the role of sympathetic nervous system in the regulation of cerebral blood flow remains controversial. Given this, the purpose of the current study was to test the hypothesis that reflex‐mediated sympathetic activation via lower body negative pressure (LBNP) blunts NVC in humans.MethodsNVC was assessed using a visual stimulation protocol (5 cycles of 30 s eyes closed and 30 s of reading) in 10 young and healthy participants (3 women; aged 25 ± 3 years). In a randomized and counterbalanced order, NVC assessments were made under control conditions and during graded sympathetic activation via LBNP at −20 mmHg and −40 mmHg. Posterior (PCA) and middle cerebral artery (MCA) mean blood velocity (vmean) were determined (transcranial Doppler ultrasound). Vertebral artery blood flow (VAflow) was measured using duplex Doppler ultrasound and vessel wall tracking software. Mean arterial pressure (finger photoplethysmography), stroke volume (Modelflow), heart rate (electrocardiogram) and the partial pressure of end‐tidal carbon dioxide (PetCO2; capnograph) were obtained. Data are presented as mean ± SD.ResultsLBNP to −20 mmHg and −40 mmHg evoked an anticipated reduction in stroke volume and increase in heart rate, while mean arterial pressure was unchanged. Prior to visual stimulation, PCAvmean and MCAvmean were not different between control, −20 LBNP and −40 LBNP conditions (P>0.05), while VAflow was reduced at −40 mmHg (P=0.02 vs. control). Under control conditions, the NVC test evoked a robust increase in PCAvmean (Δ22 ± 4%), a modest increase in MCAvmean (Δ10 ± 3%), and a moderate rise in VAflow (Δ14 ± 5%). The magnitude of these responses was unaffected by LBNP at both −20 mmHg and −40mmHg (PCAvmean Δ23 ± 4% and Δ23 ± 4%; MCAvmean Δ10 ± 1% and Δ11 ± 4%; VAflow Δ15 ± 3% and Δ16 ± 6%; P>0.05). PetCO2 decreased at −20 mmHg (37.0 ± 3.1 mmHg) and −40 mmHg (36.3 ± 3.1 mmHg) LBNP trials compared to control (40.2 ± 3.7mmHg; P=0.004).ConclusionIn summary, these findings indicate that reflex‐mediated sympathetic activation via LBNP does not blunt the NVC response in healthy humans.Support or Funding InformationFunding received from Coordination for the Improvement of Higher Education Personnel (Finance Code 001) (MS), the University of Auckland (JPF, JFRP) and the Health Research Council of New Zealand (JPF, JFRP).

Hypertension is a disease that can cause serious health issues such as acute myocardial infarction and stroke (cerebral vascular accident) and constitutes a matter of public health. Blood pressure is controlled by the cardiovascular system through various mechanisms, and the baroreceptors play a key role in this regulation. It is possible to verify the responses relevant to the control of blood pressure by stimulating these pressure sensors. It is important to understand how the baroreceptors work given the difficulty in diagnosing problems in accordance to these mechanisms. To the best of the authors's knowledge, there has been no prior study in Brazil that has statistically evaluated within the population the prevalence of problems attributed to the baroreflex system. Normalized data for different population groups are also absent. Therefore, given the difficulty in identifying the exact origin of the elevation of blood pressure and the lack of information on baroreflex within the population, we developed an equipment that is capable to determine these factors. Baroreceptors can be stimulated by applying external negative pressure through a collar positioned around the neck, in synchrony with an electrocardiogram. A decrease in the heart rate and a reduction in blood pressure are expected during the stimulation.

In this paper, the weighted-cumulated methodology designed for the objective muscle fatigue estimation using surface electromyography is improved and extended for cycling applications. An automatic signal burst segmentation is proposed for dynamic electromyography, which is robust to signal amplitude fluctuations and abrupt variation of the experimental protocol parameters. The developed algorithm is integrated into a single instrumental tool. To evaluate the proposed methodology, nine participants performed cycling exercise until muscular failure in three different experimental protocols. In the first protocol, angular velocity was kept constant and exercise power was increased. In the second protocol, power was kept constant and the angular velocity was increased. The third protocol is maintained constant in both power and angular velocity at relatively high values. During the tests, surface electromyography signal was acquired from vastus lateralis. Behavioral characteristics and performance comparison involving the proposed experimental protocols are shown. The interpretations associated with objective metric to estimate muscle fatigue are discussed. The experimental results, obtained using improved weighted-cumulated methodology, are shown to be sensitive enough to distinguish spectral signature changes in the cycling electromyographic signals associated with muscle fatigue. The weighted-cumulated methodology has been shown to be fully applicable in dynamic physical protocols such as cycling. However, the investigations point out that the specification of the experimental protocol is also very important for the results reliability.

Anais do V Congresso Brasileiro de Eletromiografia e Cinesiologia e X Simpósio de Engenharia Biomédica (978-85-5722-065-2) - Ferramenta De Coleta Telemétrica Dos Dados Da Força Aplicada Ao Pedal Instrumentado: Análise Em Tempo Real

Background Recent studies have shown that isometric handgrip (IHG) training reduces resting arterial blood pressure (BP) in both normotensive and hypertensive populations, but the mechanisms underlying these adaptations remain unclear. Furthermore, little is known regarding the effects of a single bout of IHG on the neural control of BP in humans. This becomes important given the fact that chronic adaptations may result from temporal summation of acute responses. In addition, the majority of studies regarding cardiovascular effects of IHG are performed in men and the possible sex differences in this context are unknown. Aim To test the hypothesis that neural control of BP following a single bout of IHG exercise are different between men and women. Methods Eight healthy men (24 ± 3 years) and 10 healthy women (23 ± 4 years) randomly performed a single bout (four 2‐min static contractions) of experimental (30% MVC) or sham (3% MVC) bilateral IHG exercise. All women are non‐oral contraceptives users and performed experiments in the early follicular phase of the menstrual cycle. Beat‐to‐beat heart rate (HR) and arterial BP was continuously monitored using finger photoplethysmography (Human NIBP, AD instruments) before and following IHG exercise (5–10 and 25–30 min of recovery). Spontaneous cardiac baroreflex sensitivity (cBRS) was assessed via sequence technique (CardioSeries v2.4, Brazil). Power spectral analysis of HR variability (HRV) was employed (CardioSeries v2.4, Brazil) and the ratio between low and high frequency of HRV (LF/HF) was used as a surrogate of sympathovagal balance. Results Baseline HR was greater while arterial BP and cBRS gain were lower in women compared with men ( P <0.05). Following IHG exercise, SBP increased in men (Δ7 ± 1 mmHg, 10‐min vs. rest, P <0.05), but was unchanged in women (Δ2 ± 1 mmHg, 10‐min vs. rest, P >0.05). At 10‐min following IHG exercise, HR significantly decreased (Δ‐7 ± 1 bpm, P <0.01) and remained attenuated at 30‐min time point (Δ−3 ± 1 bpm, P <0.05) in women, but was unchanged in men (10‐min: Δ−2 ± 1 bpm, and 30‐min: Δ1 ± 2 bpm, P >0.05). In women, cBRS gain significantly increased from rest at 10‐min following IHG (Δ23.7 ± 7%, P =0.01) and returned to baseline values at 30‐min of recovery (14.9 ± 2.0 ms/mmHg, P >0.05). In contrast, no differences were found in cBRS gain in men following IHG ( P >0.05). In addition, RMSSD and HF components of HRV, a proxy of cardiac vagal activity, were increased at 10‐min following IHG in women while no differences were found in men. LF/HF ratio was not affected by IHG trials. All physiological variables were unaffected by the sham protocol in both groups. Conclusion These results allow us to conclude that the acute effects of IHG exercise on neural control of BP is sex dependent and baseline sex differences in spontaneous cBRS were acutely abolished after a single bout of IHG exercise. Support or Funding Information CAPES, CNPq and FAPDF.

This paper addresses a new approach to objectively evaluate muscle fatigue in isometric and dynamic physical exertions using surface electromyography (S-EMG). The emphasis of this proposal is to preserve the spectral signature of the muscle fatigue phenomenon while reducing the spatial effects of electrode localization, and decreasing the disparity of results obtained by the same experimental protocol at different times. A cumulated and normalized modeling was sought to make evident the nonstationary characteristics of muscle fatigue that is gradually identified with its inertia and intensity. A metric involving the proposal of temporal, frequency, and time-frequency weighted-cumulated indicators is presented. Results based on real signals are shown for isometric and dynamic experimental protocols. Performance comparison of the various proposed weighted-cumulated indexes is shown and discussed. The presented approach for the objective cumulative evaluation of muscle fatigue with S-EMG signals has shown to be promising.

RESUMO Buscou-se investigar os parâmetros eletromiográficos da fadiga muscular durante exercício dinâmico realizado com resistência variável (elástica) e resistência fixa (polia). Dez homens treinados participaram voluntariamente do estudo. Foram realizadas duas contrações voluntárias isométricas máximas (CVIM) de flexão do cotovelo com 5 segundos de duração cada e 2 minutos de intervalo entre as mesmas. Em seguida, os voluntários realizaram a flexão unilateral do cotovelo até a exaustão, utilizando resistência fixa e elástica com ritmo pré-estabelecido de 2 segundos para cada fase do movimento. A resistência constante foi realizada na polia a 30% da CVIM. Para a resistência elástica, o controle de carga era baseado na percepção subjetiva de esforço do participante. A ordem do exercício foi randomizada, e o sinal de eletromiografia do músculo bíceps braquial foi registrado durante as contrações. A partir do sinal eletromiográfico referente a cada execução de movimento, foram traçadas retas de regressão linear para as variáveis RMS e frequência de potência mediana (FPM). As inclinações das retas normalizadas pelo coeficiente linear das equações de regressão foram comparadas por meio do teste t pareado. Não foram observadas diferenças significativas entre os tipos de resistência (elástica e polia). Os parâmetros eletromiográficos de fadiga não foram diferentes durante o exercício de flexão do cotovelo realizado com resistência elástica e polia. A percepção de esforço durante o exercício com implemento elástico não influencia no padrão do sinal eletromiográfico (RMS e FPM).

Objetivo: Avaliar os desequilíbrios musculares em atletas de ginástica feminina e correlacionar com a idade. Metodologia: 24 ginastas femininas de 9 a 15 anos tiveram os desequilíbrios musculares do joelho avaliados por meio de dinamômetro isocinético. Resultados: A razão I/Q demonstrou que 87,5% das ginastas apresentaram risco de lesão nos membros dominante e 91% no não dominante. Os desequilíbrios bilaterais revelaram 25% das ginastas com desequilíbrio bilateral superior a 10% no quadríceps e 30% nos isquiotibiais. Não foram encontradas correlações entre os desequilíbrios musculares e a idade das ginastas. Conclusão: Jovens ginastas apresentam desequilíbrios musculares que podem estar relacionados a possíveis lesões nos membros inferiores.