Comparison of the Polar S810i monitor and the ECG for the analysis of heart rate variability in the time and frequency domains.

The aim of the present study was to compare heart rate variability (HRV) at rest and during exercise using a temporal series obtained with the Polar S810i monitor and a signal from a LYNX(R) signal conditioner (BIO EMG 1000 model) with a channel configured for the acquisition of ECG signals. Fifteen healthy subjects aged 20.9 +/- 1.4 years were analyzed. The subjects remained at rest for 20 min and performed exercise for another 20 min with the workload selected to achieve 60% of submaximal heart rate. RR series were obtained for each individual with a Polar S810i instrument and with an ECG analyzed with a biological signal conditioner. The HRV indices (rMSSD, pNN50, LFnu, HFnu, and LF/HF) were calculated after signal processing and analysis. The unpaired Student t-test and intraclass correlation coefficient were used for data analysis. No statistically significant differences were observed when comparing the values analyzed by means of the two devices for HRV at rest and during exercise. The intraclass correlation coefficient demonstrated satisfactory correlation between the values obtained by the devices at rest (pNN50 = 0.994; rMSSD = 0.995; LFnu = 0.978; HFnu = 0.978; LF/HF = 0.982) and during exercise (pNN50 = 0.869; rMSSD = 0.929; LFnu = 0.973; HFnu = 0.973; LF/HF = 0.942). The calculation of HRV values by means of temporal series obtained from the Polar S810i instrument appears to be as reliable as those obtained by processing the ECG signal captured with a signal conditioner.

Comparison of the Polar S810i monitor and the ECG for the analysis of heart rate variability in the time and frequency domains

The aim of the present study was to compare heart rate variability (HRV) at rest and during exercise using a temporal series obtained with the Polar S810i monitor and a signal from a LYNX® signal conditioner (BIO EMG 1000 model) with a channel configured for the acquisition of ECG signals. Fifteen healthy subjects aged 20.9 ± 1.4 years were analyzed. The subjects remained at rest for 20 min and performed exercise for another 20 min with the workload selected to achieve 60 percent of submaximal heart rate. RR series were obtained for each individual with a Polar S810i instrument and with an ECG analyzed with a biological signal conditioner. The HRV indices (rMSSD, pNN50, LFnu, HFnu, and LF/HF) were calculated after signal processing and analysis. The unpaired Student t-test and intraclass correlation coefficient were used for data analysis. No statistically significant differences were observed when comparing the values analyzed by means of the two devices for HRV at rest and during exercise. The intraclass correlation coefficient demonstrated satisfactory correlation between the values obtained by the devices at rest (pNN50 = 0.994; rMSSD = 0.995; LFnu = 0.978; HFnu = 0.978; LF/HF = 0.982) and during exercise (pNN50 = 0.869; rMSSD = 0.929; LFnu = 0.973; HFnu = 0.973; LF/HF = 0.942). The calculation of HRV values by means of temporal series obtained from the Polar S810i instrument appears to be as reliable as those obtained by processing the ECG signal captured with a signal conditioner.

Relação entre a tensão aplicada e a sensação de desconforto nos músculos isquiotibiais durante o alongamento / Relationship between tension applied and sensations of discomfort in the hamstring muscle during stretching

CONTEXTUALIZAÇÃO: O alongamento muscular é amplamente empregado no tratamento e na prevenção de doenças musculoesqueléticas. Estudos utilizam informações subjetivas do paciente como "desconforto" e "tensão sem dor" para limitar intensidade de alongamento, sem estabelecer uma tensão adequada de estiramento. OBJETIVO: Estudar a relação entre tensão aplicada e informações subjetivas, durante alongamento estático passivo para analise da reprodutibilidade e variações nas informações sensoriais. MÉTODOS: Participaram 20 jovens com idade média de 20 anos (±2,25), sem experiência prévia com programa de alongamento, divididos em dois grupos: G1 - participou de programa de alongamento dos músculos isquiotibiais, G2 sem programa de alongamento. Os grupos foram submetidos a três avaliações para mensurar o torque e a atividade eletromiográfica (EMG), nas posições de sensação de desconforto (SD) sem dor e sensação de desconforto com dor (SDD), por meio de um sistema de aquisição de sinais, constituído de condicionador de sinais, eletrodo bipolar ativo de superfície, célula de carga, eletrogoniômetro, sensor de pressão e modelo biomecânico. RESULTADO: As análises do torque nas posições SD e SDD revelaram comportamento semelhante nos dois grupos, sem diferenças significantes entre as três avaliações (P > 0.05), demonstrando reprodutibilidade das informações subjetivas dos grupos nas duas posições. A EMG nas posições de SD e SDD não mostrou diferença significante com a EMG obtida em repouso. CONCLUSÃO: Este trabalho revelou que a informação da sensação subjetiva de alongamento é confiável, segura e possível de ser reproduzida clinicamente.

BACKGROUND: Muscle stretching is widely used in the prevention and treatment of musculoskeletal diseases. Previous studies have used subjective information like "discomfort" and "tension without pain" for limiting the intensity of stretching, but without establishing appropriate tensions for stretching. OBJECTIVE: To study the relationship between applied tension and subjective information during static passive stretching, in order to analyze the reproducibility and variability of sensorial information. METHOD: Twenty subjects (mean age: 20 ± 2.25 years) without previous experience of stretching programs were recruited and divided into two groups. G1 participated in a hamstring muscle stretching program, while G2 did not follow a stretching program. Both groups underwent three evaluations to quantify torque and electromyographic activity, in positions that produced a sensation of discomfort without pain (SD) and a sensation of discomfort with pain (SDP), using a signal acquisition system consisting of a signal conditioner, active bipolar surface electrode, load cell, electrogoniometer, pressure sensor and biomechanical model. RESULTS: The torque analyses in the SD and SDP positions showed similar behavior in the two groups, without significant differences between the three evaluations (p > 0.05), thereby demonstrating the reproducibility of the subjective information from the groups in the two positions. Electromyography in the SD and SDP positions did not show significant differences in relation to the findings at rest. CONCLUSION: This study demonstrated that the subjective information on stretching sensations is reliable and secure, and can be reproduced clinically.

Hybrid expert system for decision supporting in the medical area: complexity and cognitive computing.

This paper proposes a hybrid expert system (HES) to minimise some complexity problems pervasive to the artificial intelligence such as: the knowledge elicitation process, known as the bottleneck of expert systems; the model choice for knowledge representation to code human reasoning; the number of neurons in the hidden layer and the topology used in the connectionist approach; the difficulty to obtain the explanation on how the network arrived to a conclusion. Two algorithms applied to developing of HES are also suggested. One of them is used to train the fuzzy neural network and the other to obtain explanations on how the fuzzy neural network attained a conclusion. To overcome these difficulties the cognitive computing was integrated to the developed system. A case study is presented (e.g. epileptic crisis) with the problem definition and simulations. Results are also discussed.

A hybrid expert system for the diagnosis of epileptic crisis.

This work presents a hybrid expert system (HES) intended to minimise some complex problems pervasive to knowledge engineering such as: the knowledge elicitation process, known as the bottleneck of expert systems; the choice of a model for knowledge representation to codify human reasoning; the number of neurons in the hidden layer and the topology used in the connectionist approach; the difficulty to extract an explanation from the network. Two algorithms applied to developing of HES are also suggested. One of them is used to train the fuzzy neural network and the other to obtain explanations on how the fuzzy neural network attained a conclusion. A case study is presented (e.g. epileptic crisis) with the inclusion of problem definition and simulations. The results are also discussed.

Connectionist expert systems as medical decision aid.

In this paper neural networks are used as associative memories to build an expert system for aiding medical diagnosis. As in expert systems using symbolic manipulation, the knowledge is introduced by a knowledge engineer using a collection of known cases. The system has an object-oriented approach to knowledge organization and the resulting network topology. Fuzzy sets are used to interpret connection values and/or excitation state of the units. The main result is that the proposed neural network allows not only finding a solution in some cases, but also suggests obtaining more clinical data if the data available is insufficient to reach a conclusion. This approach is illustrated by examples.