• Automatic threshold determination for a local approach of change detection in long-term signal recordings

      El Falou, Wassim; Khalil, Mohamad; Duchêne, Jacques; Hewson, David; Université de Technologie de Troyes; Université Libanaise (Hindawi, 2007-12-01)
      CUSUM (cumulative sum) is a well-known method that can be used to detect changes in a signal when the parameters of this signal are known. This paper presents an adaptation of the CUSUM-based change detection algorithms to long-term signal recordings where the various hypotheses contained in the signal are unknown. The starting point of the work was the dynamic cumulative sum (DCS) algorithm, previously developed for application to long-term electromyography (EMG) recordings. DCS has been improved in two ways. The first was a new procedure to estimate the distribution parameters to ensure the respect of the detectability property. The second was the definition of two separate, automatically determined thresholds. One of them (lower threshold) acted to stop the estimation process, the other one (upper threshold) was applied to the detection function. The automatic determination of the thresholds was based on the Kullback-Leibler distance which gives information about the distance between the detected segments (events). Tests on simulated data demonstrated the efficiency of these improvements of the DCS algorithm.
    • Evaluation of driver discomfort during long-duration car driving

      El Falou, Wassim; Duchêne, Jacques; Grabisch, Michel; Hewson, David; Langeron, Yves; Lino, Frédéric; Université de Technologie de Troyes; Université Pierre et Marie Curie; Laboratory of Accidentology, Biomechanics and Human Behaviour (Elsevier, 2003-05-31)
      The evolution of indices of fatigue, discomfort, and performance of subjects seated for long duration (150 min) in car seats were studied (n=11). Four experimental configurations were used: with and without vibration for two seats (U, uncomfortable; C, comfortable). Surface electromyography (SEMG) data were recorded bilaterally from cervical erector spinae and external oblique muscles. Discomfort increased significantly during the trial, regardless of the experimental condition (p<0.05). Performance was significantly worse for seat U with vibration (p<0.05). The median frequency of SEMG signals did not change between experimental conditions or across time. It would appear that, either the level of discomfort experienced was insufficient to change either performance or SEMG measures, or that the large parameter estimation variance of the SEMG signals might have masked any underlying spectral change. Further refinement of the SEMG signal processing methodology may be necessary to be able to detect fatigue of postural muscles.
    • Influence of elbow position and handle size on maximal grip strength

      Li, Ke; Hewson, David; Hogrel, Jean-Yves; Université de Technologie de Troyes; Université Paris (SAGE Publications, 2009-10-21)
    • Recurrence quantification analysis of sustained sub-maximal grip contractions in patients with various metabolic muscle disorders

      Li, Ke; Hewson, David; Snoussi, Hichem; Duchêne, Jacques; Hogrel, Jean-Yves; Université de Technologie de Troyes; Shandong University; Université Paris (Elsevier, 2010-11-01)
      Recurrence quantification analysis (RQA) was used to analyse force signals during sustained sub-maximal grip contraction (SSGC) of three types of patients suffering from a metabolic muscle disorder (glycogen storage disease type III (GSD III), glycogen storage disease type V (GSD V) and mitochondrial myopathies (MITO)) compared to control subjects. Recurrence plots (RP) of patients showed clear non-uniformity, in comparison to control subjects who displayed quasi-periodic patterns. Quantitative analysis of the RP showed significant differences between patients with metabolic disorders and the control group for four RQA parameters. The results showed that the SSGC signals of patients had decreased Lmax, which indicated more chaotic patterns. In addition the deterministic component of the signals was less complex for patients than for controls. The differences of SSGC signal observed using RP and RQA were possibly related to the underlying changes in metabolism of muscle fibres due to the disease. Results of this study illustrate that the RQA technique is well suited to analyse sustained grip-force signals.
    • Surface electromyography as a tool to assess the responses of car passengers to lateral accelerations. Part II: Objective comparison of vehicles

      Farah, G.; Petit-Boulanger, C.; Hewson, David; Duchêne, Jacques; Université de Technologie de Troyes; Technocentre Renault (Elsevier, 2006-02-02)
      The purpose of this study was to objectively assess the response of car passengers to lateral accelerations. Surface EMG signals were collected bilaterally from the cervical erector spinae (CES), latissimus dorsi (LD), erector spinae (ES), external oblique (EO), and vastus lateralis (VL) muscles of 10 subjects. Lateral acceleration was also recorded. Three chassis-seat configurations AA, BA and BB were tested, with the first letter denoting the chassis and the second the seat. SEMG signals were often contaminated by noise, and were, therefore, denoised using the methods explained in part I. Reciprocal phasic activity was observed for all muscles except for the EO, and the reaction of passengers to lateral accelerations was interpreted as a bust torsion. The RMS of EMG segments was used as an indication of muscle activity. Muscle activation of VL and ES were significantly affected by the configuration tested (p < 0.05), with greater activation levels observed for the chassis A than for the chassis B. Such a finding implies that greater roll requires greater muscle activity, thus resulting in less comfortable vehicles. Therefore, SEMG can be used to provide an objective measure of discomfort in passengers subjected to lateral accelerations in a car seat.
    • Surface electromyography as a tool to assess the responses of car passengers to lateral accelerations: Part I. Extraction of relevant muscular activities from noisy recordings

      Farah, G.; Hewson, David; Duchêne, Jacques; Université de Technologie de Troyes; Technocentre Renault (Elsevier, 2006-02-02)
      The aim of this paper is to develop a method to extract relevant activities from surface electromyography (SEMG) recordings under difficult experimental conditions with a poor signal to noise ratio. High amplitude artifacts, the QRS complex, low frequency noise and white noise significantly alter EMG characteristics. The CEM algorithm proved to be useful for segmentation of SEMG signals into high amplitude artifacts (HAA), phasic activity (PA) and background postural activity (BA) classes. This segmentation was performed on signal energy, with classes belonging to a χ2 distribution. Ninety-five percent of HAA events and 96.25% of BA events were detected, and the remaining noise was then identified using AR modeling, a classification based upon the position of the coordinates of the pole of highest module. This method eliminated 91.5% of noise and misclassified only 3.3% of EMG events when applied to SEMG recorded on passengers subjected to lateral accelerations.
    • Theme D: sensors, wearable devices, intelligent networks and smart homecare for health

      Campo, E.; Hewson, David; Gehin, C.; Noury, N.; CNRS; Université de Toulouse; Université de Technologie de Troyes; University of Lyon (Elsevier, 2013-02-11)
      This paper presents the activities of the research group in sensors, wearable devices, intelligent networks and smart homecare for health inside the GdR STIC-Santé. Four research fields are covered: sensors, clothing, housing and networks, to allow better monitoring of health parameters and quality of life. Several events were organized or co-organized during the period 2011–2102. They were devoted to the issue of the autonomy of people with a particular focus on the needs and expectations and also the embedded technologies developed to enable monitoring of health parameters and activities in their living environment. Future projects will try to complete the knowledge of the current work on frailty and the risks incurred, in particular falls, and identify opportunities to share the achievements of the research teams to respond to National or European projects calls.
    • Validation of balance-quality assessment using a modified bathroom scale

      Hewson, David; Duchêne, Jacques; Hogrel, Jean-Yves; Université de Technologie de Troyes (Institute of Physics, 2015-01-13)
      The balance quality tester (BQT), based on a standard electronic bathroom scale has been developed in order to assess balance quality. The BQT includes automatic detection of the person to be tested by means of an infrared detector and bluetooth communication capability for remote assessment when linked to a long-distance communication device such as a mobile phone. The BQT was compared to a standard force plate for validity and agreement. The two most widely reported parameters in balance literature, the area of the centre of pressure (COP) displacement and the velocity of the COP displacement, were compared for 12 subjects, each of whom was tested on ten occasions on each of the 2 days. No significant differences were observed between the BQT and the force plate for either of the two parameters. In addition a high level of agreement was observed between both devices. The BQT is a valid device for remote assessment of balance quality, and could provide a useful tool for long-term monitoring of people with balance problems, particularly during home monitoring.
    • Wavelet transform analysis of the power spectrum of centre of pressure signals to detect the critical point interval of postural control

      Singh, Neeraj Kumar; Snoussi, Hichem; Hewson, David; Duchêne, Jacques; Université de Technologie de Troyes (Springer, 2010-12-31)
      The aim of this study was to develop a method to detecting the critical point interval (CPI) when sensory feedback is used as part of a closed-loop postural control strategy. Postural balance was evaluated using centre of pressure (COP) displacements from a force plate for 17 control and 10 elderly subjects under eyes open, eyes closed, and vibration conditions. A modified local-maximum-modulus wavelet transform analysis using the power spectrum of COP signals was used to calculate CPI. Lower CPI values indicate increased closed-loop postural control with a quicker response to sensory input. Such a strategy requires greater energy expenditure due to the repeated muscular interventions to remain stable. The CPI for elderly occurred significantly quicker than for controls, indicating tighter control of posture. Similar results were observed for eyes closed and vibration conditions. The CPI parameter can be used to detect differences in postural control due to ageing.