Nicolas Houel

Relationships between each part of the spinal curves and upright posture using Multiple stepwise linear regression analysis

Back pain is a common reason for consultation in primary healthcare clinical practice, and has effects on daily activities and posture. Relationships between the whole spine and upright posture, however, remain unknown. The aim of this study was to identify the relationship between each spinal curve and centre of pressure position as well as velocity for healthy subjects. Twenty-one male subjects performed quiet stance in natural position. Each upright posture was then recorded using an optoelectronics system (Vicon Nexus) synchronized with two force plates. At each moment, polynomial interpolations of markers attached on the spine segment were used to compute cervical lordosis, thoracic kyphosis and lumbar lordosis angle curves. Mean of centre of pressure position and velocity was then computed. Multiple stepwise linear regression analysis showed that the position and velocity of centre of pressure associated with each part of the spinal curves were defined as best predictors of the lumbar lordosis angle (R(2)=0.45; p=1.65*10-10) and the thoracic kyphosis angle (R(2)=0.54; p=4.89*10-13) of healthy subjects in quiet stance. This study showed the relationships between each of cervical, thoracic, lumbar curvatures, and centre of pressures fluctuation during free quiet standing using non-invasive full spinal curve exploration.

Mechanics of standing and crouching sprint starts

ABSTRACT The aim of this study was to compare the kinetic and kinematic parameters of standing and crouch sprint starts. Parallel starts (PS), false starts (FS), jump starts (JS) and crouch starts (3PS) were compared. Eighteen participants performed each start on a force plate and six infrared cameras captured the three-dimensional coordinates of 36 retro-reflective markers. Performance during a five-metre sprint (T5m) was analysed. Duration of the start phase (Tstart), mean values of horizontal and total ground reaction forces (GRFs) (Fx_mean and Ftot_mean), ratio of force (RF), maximal power (Pmax) and kinetic energy (KE) of each limb were calculated. Significant differences were found for T5m, Tstart, KE, Pmax, Fx_mean, Ftot_mean and RF for the crouch start compared to the other starts (P ≤ 0.05). Significant correlations were found between T5m and Tstart (r = 0.59; P ≤ 0.001), and T5m and Pmax, Fx_mean and RF (−0.73 ≤ r ≤ −0.61; P ≤ 0.001). To conclude, the crouch start resulted in the best performance because Tstart was shorter, producing greater Pmax, Fx_mean with a more forward orientation of the resultant force. Greater KE of the trunk in each start condition demonstrated the role of the trunk in generating forward translation of the centre of mass (CM).

Stimulated infrared thermography applied to differentiate scar tissue from peri-scar tissue: a preliminary study

Abstract Every human injury leads to a scar formation. The healing process leads to the formation of new tissue: the scar, which is different from the original tissue. This process is influenced by mechanical strength and the local vasculature is modified. The purpose of this study is to show that there are various temperatures between the scar and the peri-scar area associated with the healing process that can be estimated using the thermal infrared camera. In the study, 12 scars were stimulated by cold. Several changes of temperature were observed between scar and peri-scar area for 10 min. Scars appeared significantly colder with a Wilcoxon test (p = 0.01). Results showed that stimulated infrared thermography can be used to monitor the temperature difference between the scar and peri-scar tissue.

Validity of 3D reconstruction of a new tool for postural assessmentbased on a single optical camera

Several techniques for balance assessment coexist, either for clinical or research purposes (Yeung et al. 2014; Boulet et al. 2016; Dinu et al. 2016). The gold standard remains measurements of the Center of Pressure (CoP) coordinates using a force plate. From the CoP data, several models for Center of Mass (CoM) reconstruction have been developed. However, these do not take into consideration body segments posture and their influence on the CoM during quiet standing. For these reasons, many authors have developed direct CoM modeling using various technologies (Vicon® (Boulet et al. 2016), inertial sensors (Dinu et al. 2016), thermal imaging (Clark et al. 2012; Yeung et al. 2014), 3D camera (Placidi et al. 2014), multiple camera setting (Corazza and Andriacchi 2009), etc.). The issue of the technological cost and its impact on the clinical accessibility has brought a will to develop low-cost tools. In this context, our goal is to develop a protocol allowing a 3D modeling of body segments and the CoM using Direct Linear Transformation (DLT method, based on Abdel-Aziz & Karara’s equations (Abdel-Aziz and Karara 1971)). The aim of this study is to estimate accuracy and reliability of static 3D reconstruction based on a single low-cost camera and mirrors.

Principal Componant Analysis between perceptions and kinematics of the subject. An ergonomic case study at office work

Nowadays, musculoskeletal disorders (MD) account for 80% of professional pathologies (INRS 2008). MD contains the peri-articular pathologies that affect muscles, articulations and nerves (INRS 2008). World Health Organization published a report in 2004 that showed prevalence of lumbar back pain was about 60%. The main risks factors of MD are repeatability of a task, bad posture maintaining and static muscle activity (INRS 2008). Videman et al (1990) showed a relationship between back pain and office working according to their low activity. Identification and prevention of risk of MD are usually based on ergonomic studies. Ergonomy focuses on comfort and discomfort, specially with sitting workers. However, few studies have been carried out in order to connect the cognitive approach and biomechanics, aiming to better evaluate the links between the biomechanics of comfort and its perception by a subject (Baucher and Leborgne 2006). These studies interested only on the subjectives comfort’s parameters and postural balance of the subject regardless of the upper joint or spine kinematics. The aim of this study is to show the relationships between comfort’s perception and biomechanics. This approach presents through a case study.

Evaluations of cranial micro-motion and breathing using kinematic analysis. Comparaison between Vicon system and spirometry

Inside human body, various rhythmic impulses with range of time less than a second to years correspond to different physiological changes (Goldbeter 2005). Among these rhythmic impulses, blood pressure, heart rate and breathing have been usually studied. Blood pressure, heart rate and breathing are now used in order to define frequencies associated with control of autonomic nervous system (Task Force 1996). Studying these frequencies is needed to better understand and evaluate human homeostatic control. Some of these frequencies could be assessed by cranial and sacral osteopathic manipulative perception (OMP) (Nelson 2006). This osteopathic manipulative perception has been initially developed by (Sutherland 1939). To our knowledge, few studies have observed good reliability between OMP and scientific assessment in order to measure cranial rhythmic impulse (CRI) (Nelson 2006). These studies used laser doppler blood flow to show relationships between: i) 0.02 Hz frequency that could be associated with thermoregulation, ii) 0.1 Hz and 0.25 Hz that could be associated with sympathetic baroreflex sensitivity, iii) 0.39 Hz frequency that could be associated with vagal reflex response (Nelson 2006). Osteopathic and scientific communities focused on the specific frequencies analysis of human rhythms and tried to develop accurate devices that can assess to CRI. Nowadays, non-invasive and easily devices and sensors are developed in order to monitor heart rate (Shafiq 2014, Chan 2013). Other non-invasive devices like eddy currents sensors have been used in order to estimate cranial micro-motion on skin (Stubbe 2015). However, if Stubbe et al have shown cranial three dimensional motion using a eddy current, more sensors or markers are needed to define more accurately conformational change of the head. On another point of view, Shafiq & Veluvolu have shown that kinematics analysis like Vicon system can be used in order to assess to human micro-motion like heart rate monitoring (Chan 2013). The aim of the present study is to define if kinematic analysis can estimate micro-motion frequency on head’s skin of the subject during imposed breathing.

Poster Session II, July 14th 2010 — Abstracts: Cinalysis: A new software for swimming races analysis

Abstract Since a few years, performance analysis during a sport event became a key point to understand and improve athletes’ performance. Nevertheless, as during football and basketball games, these analyses are often statistical analysis. No kinematic data are collected. Performance analysis during swimming races also follows this trend. The most widely used software (swimwatch, …) designed for swimming races analysis only provide data such as mean stroke lengths, mean stroke frequencies, start distance and turns distances. Moreover the collected data remain inaccurate and unfaithful. Cinalysis is a new software which aimed to collect accurate kinematic data in real-time and markerless conditions. This software aim to be used by swimmers’ coaches or scientists and aim to measure instantaneous swimmers position and velocity from the images collected with a single fixed or moving camcorder. Camcorder could be placed anywhere on the poolside, but should rather be located at the top of the bleachers. Specific algorithms have been developed in order to automatically track the swimmer head. An algorithm for single moving camcorder calibration has also been developed. This algorithm works with every kind of camcorder. Internal camcorder parameters are estimated at the beginning of the evaluation session using a simple planar calibration rig. The internal parameters must be constant during the whole analysis. External camcorder parameters are initially computed and refreshed for each image. Finally, a semi-automatic signal processing toolbox has also been included in the software. A pilot study has been led during an international competition in 2008 (the French EDF meeting). The results’ analysis of this study allows showing that cinalysis succeeded to collect classic data but also succeeded to collect accurate kinematic data. These data allow a complete analysis of the race strategy and allow identifying the velocity loss induced by technical mistakes. The software also allows realizing the many between swimmers comparisons.