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Sensorized insoles (SIs) have been used as a wearable instrument to study human gait and have the potential to identify and predict pathologies and injuries. However, most of these sensorized insoles are only statically calibrated, relying on a scale and known weights to establish a relationship between electrical signals and the load applied on laboratory benches while ignoring the dynamic interaction between person and instrument. This study proposes and verifies a calibration method complementary to static calibration to compensate for different dynamic interactions between the insole and the individual during gait. In order to perform this comparison, a laboratory test was proposed with 32 volunteers (18 men and 14 women). Each volunteer walked on a double-belt instrumented treadmill (Bertec at 1000 Hz, Bertec Corp, Columbus, OH) while wearing an experimental resistive sensorized insole (SI). The SI data were compared with the instrumented treadmill and adjusted using an optimization algorithm to create a dynamic coefficient to complement and optimize the results. This study also verifies the impact of the method considering three different types of gait: pronated, neutral, and supinated. After using this technique and considering static calibration, the Pearson correlation coefficient between the SI and the instrumented treadmill improved by 12%.

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ABSTRACT Objective: To evaluate if participants, subjected to whole-body vibration, two different types of media (paper versus tablet) and two lighting environments (fluorescent versus LED), present a difference in eye-movement parameters during reading tasks. Methods: Fourteen adults silently read two different texts in each one of the eight randomized testing conditions (whole-body vibration versus media versus lighting), resulting in 16 different texts read per individual. Whole-body vibration was applied in the vertical direction, 5Hz and 0.8 m/s2 root-mean-square amplitude, a condition similar to those experienced by forklift truck drivers. Participants were in a sitting position with a backrest. An eye-tracker evaluated the eye-movements during the reading task. Results: Whole-body vibration significantly reduced the number of ocular fixations, and cross-correlation; and increased the reading efficiency, fixation duration, directional attack, and binocular anomalies. Neither the type of media nor the lighting environment interfered significantly with the eye-movements, both in situations with and without vibration. Conclusion: The results indicate that whole-body vibration interfered in the eye-movements during the reading task. This may impose a difficulty to process the visual information and to synchronously coordinate the binocular movements under vibration environments.

RESUMO Objetivo: Avaliar se participantes submetidos à vibração de corpo inteiro, a dois tipos diferentes de mídia (papel versus tablet) e a dois ambientes de iluminação (fluorescente versus LED) apresentam diferença nos parâmetros de movimento dos olhos durante tarefas de leitura. Métodos: Quatorze adultos leram silenciosamente dois textos diferentes em cada uma das oito condições de teste (vibração de corpo inteiro versus mídia versus iluminação), de forma aleatória, resultando em 16 textos diferentes lidos por indivíduo. A vibração de corpo inteiro foi aplicada no sentido vertical, com amplitude de 5Hz e 0,8m/s² da raiz do valor quadrático médio, em condição semelhante às vivenciadas pelos motoristas de empilhadeiras. Os participantes permaneceram em postura sentada com encosto. Um rastreador ocular avaliou os movimentos oculares durante a leitura. Resultados: A vibração de corpo inteiro reduziu significativamente o número de fixações oculares e a correlação cruzada entre os olhos e aumentou a eficiência de leitura, duração da fixação, ataque direcional e anomalias binoculares. Nem o tipo de mídia nem as condições de ambientes de iluminação interferiram significativamente nos movimentos oculares, tanto em situações com ou sem vibração. Conclusão: Os resultados indicam que a Vibração de Corpo Inteiro pode interferir nos movimentos oculares durante a leitura. Isso pode impor uma dificuldade no processamento da informação visual e na coordenação síncrona dos movimentos binoculares em ambientes de vibração.

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This study verified typing performance on smartphones of public transportation passengers using subjective assessments of comfort and difficulty and objective assessments of the number of errors and typing speed. Three frequency values (5, 10, and 15 Hz), two magnitudes (0.6 and 1.2 m/s2) and two types of operating systems (Android and IOS) were adopted. Tests without vibration were applied to analyse the residual effect of vibration. The results showed that vibration significantly influences comfort. The higher the frequency, the less errors and the faster the typing speed. In the magnitude analysis, the increase caused a greater number of errors and greater difficulty. In both assessments, the discomfort was proportional to the increase in frequency or magnitude and the number of errors was inversely proportional to the typing speed. Finally, the IOS operating system showed worse comfort when compared to Android, although no significant differences were observed for the objective assessment. Practitioner summary: Public transportation passengers are exposed to WBV while typing on smartphones. The results showed that vibration influences comfort, the number of errors and the typing speed. Therefore, manufacturers should be aware of the level of vibration that vehicles are exposed to in order to provide more performance to the user. Abbreviations: WBV: whole-body vibration; PID: proportional-integral-derivative; RMS: root mean square; HLM: hierarchical linear modeling; OLS: ordinary least squares; STH: seat-to-head.

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BACKGROUND: Students, as well as other professional drivers, must have focus to adequately perform their tasks. However, they are subjected to whole-body vibration (WBV) in their journey to school or work. OBJECTIVE: To investigate the influence of in-loco WBV exposure on focus, both instantaneously, as well as residually. Analysis is performed for both genders, as well as for the presence of Attention Deficit Hyperactivity Disorder (ADHD). METHODS: Using a tablet computer, 20 volunteers played a focus game available on an app for brain training while exposed or not exposed to WBV. The exposure was that of a car travelling on a stone paved route. The performance measure was the score provided at the end of each game. Subjective comfort and difficulty evaluations were also investigated. RESULTS: The results suggest that WBV had a negative effect on the focus performance. However, it proved positive three minutes after the exposure (residual effect). The mean scores of females were higher than for males for most of the tests, apart from the one under WBV although at the expense of getting more discomfort. The difficulty level was not different within the gender groups. CONCLUSION: It could be concluded that the group with ADHD had a small but positive influence on the results for most of the tests, indicating that they are less affected by the presence of WBV. Since many students and workers have ADHD, this may be considered an important finding. It was shown that objective results should not be the only measures to use, as the subjective evaluation may explain the results better.

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A simple, low cost and easy-to-operate 3D stereophotogrammetry system was developed to measure the kinematic pattern of head stabilisation during visual tasks. The system differs from commercially available ones since it: (a) takes into account the gaze motor coordination characteristics and measures the head translations quantified at the point that best represents the translations caused by the eyes' movement during visual tasks, that is, the midpoint between the eyes; (b) offers minimum restriction to the head movement and minimum interference with it; (c) innovates when using the position coordinates produced by a free-online tracker software. The system was effective in recording the head movements and its RMS total error was 0.705 mm with ±0.808 mm standard deviation. This represents an RMS total error of 3.5%, considered satisfactory because it provided results with a confidence level higher than 95%. The system was effective to record differences in head movements of 11 individuals in open and closed eyes conditions and revealed the direction-specific feature of the head displacements size. The results showed that the system is a cost-effective and accurate alternative for studies needing to accurately measure head movements during visual tasks.

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