Samuel Crequy

Performance of wavelet denoising in vibration analysis: highlighting

This paper proposes to highlight two aspects of denoising in vibration analysis. The first aspect aims to reveal the singularities, and the second eliminates the noise in order to keep the useful signal. These two aspects are the cause of the surjection of denoising, especially due to the choice of the performance criteria. This paper highlights the use of denoising through these aspects, and then proposes a performance criterion suitable for vibration analysis as part of a noise suppression, to apply a processing method. This paper provides a reflection on the use of discrete wavelet transform through the various parameters which are used during processing.

Hand-arm vibration in cycling

Numerous workers are exposed to vibrations which can turn out to be fatal for the health. Athletes can be included in this population, in particular cyclists who are exposed to vibration due to the irregularity of the road. This nuisance depends of the duration of exposure and the range of vibrations. While the worker is mostly directly excited by a vibrating system, the cyclist is indirectly subjected to it. He undergoes the vibrations of an excited sub-structure which is the bicycle. So the bicycle plays the role of a vibration filter or amplifier. In this paper we propose to (i) study the transmission of vibrations to the cyclist after excitation on a paving road, (ii) calculate the limit time of exposure to this type of excitation rate by the use of the standard ISO 5349 and the European directive 2002/44/EC, and (iii) compare the weighting curve of the standard with a vibrations transmissibility curve obtained between the collarbone and the stem. For this particular case of an excited sub-structure, a weighting curve is proposed by considering the first modal frequency of the bicycle.

Validity and reliability of the G-Cog BMX Powermeter.

The aim of this study was to test the validity and reliability of the G-Cog which is a new BMX power meter allowing for the measurements of the power output (250 Hz) at the BMX rear wheel during actual cycling and laboratory conditions. Sprints in road cycling (6-8 s) from static start and incremental tests in the laboratory (100-400 W) have been performed to analyse the validity and reliability of the power output values by comparison with 2 devices: The PowerTap and the SRM which are considered as the gold standard. The most important finding of this study is that the G-Cog power output data were not valid and reliable during sprint and standardised laboratory tests compared with the SRM and the PowerTap devices. During the sprint and the laboratory tests the ratio limits of agreement of the power output differences between the SRM and G-Cog were 1.884×÷1.970 (95% CI = .956-3.711) and 12.126×÷16.281 (95% CI = 0.745-197.430), respectively. In conclusion, the G-Cog must be used with caution regarding the power output measurements. Nevertheless, the G-Cog could be used for the first time to analyse the determinants of the BMX performance from the pedalling profile.

Validity and reliability of the G-Cog device for kinematic measurements.

The aim of this study was to test the validity and the reliability of the G-Cog which is a new BMX powermeter allowing for the measurements of the acceleration on X-Y-Z axis (250 Hz) at the BMX rear wheel. These measurements allow computing lateral, angular, linear acceleration, angular, linear velocity and the distance. Mechanical measurements at submaximal intensities in standardized laboratory conditions and during maximal exercises in the field conditions were performed to analyse the reliability of the G-Cog accelerometers. The performances were evaluated in comparison with an industrial accelerometer and with 2 powermeters, the SRM and PowerTap. Our results in laboratory conditions show that the G-Cog measurements have low value of variation coefficient (CV=2.35%). These results suggest that the G-cog accelerometers measurements are reproducible. The ratio limits of agreement of the rear hub angular velocity differences between the SRM and the G-Cog were 1.010 × ÷ 1.024 (95%CI=0.986-1.034) and between PowerTap and G-Cog were 0.993 × ÷ 1.019 (95%CI=0.974-1.012). In conclusion, our results suggest that the G-Cog angular velocity measurements are valid and reliable compared with SRM and PowerTap and could be used to analyse the kinematics during BMX actual conditions.

Vibration of the upper limbs in cycling

Exposure to vibrations can cause discomfort. It can negatively affect performances and is risky for health and for the safety of humans. In particular, the hand–arm system may suffer from vascular diseases, neurological diseases, carpal tunnel syndrome and musculoskeletal disorders (Friden 2001). The standard ISO 5349 defines the procedure of vibratory measure and defines the thresholds of security. While cycling, a cyclist is subject to these phenomena. Particularly, the cyclist suffers from the nerve tunnel syndrome and from tendinitis (Akuthota et al. 2005). Many studies (Subashia et al. 2008) are targeted to analytical and numerical modelling of hand–arm system for the worker. This work provides tools to design or predict the user’s position to overcome negative vibrations and to reduce drudgery for the cyclist. After a presentation of vibration theory of body and of the standards, we in this paper propose a 5 degrees of freedom (DOF) system to illustrate the vibrations of the hand–arm systems in the hands arm of a cyclist and its coupling with the bike. This model is updated in the laboratory and validated on a paved road of Reims.

Vibration transmissibility in different body positions with various vibration frequencies in a vertical vibration platform

Whole body vibration training (WBVT) is a neuromuscular stimulation applied as a mean of exercise and rehabilitation to improve muscle strength, bone mineral density and body balance (Rittweger 2010). The benefits of vibration training must be considered with the potential physiological hazards associated with the exposure to vibration. Indeed, it is well known from occupational medicine that prolonged exposure to WBV can have major health hazards, such as low-back pain and Raynaud’s syndrome (Bovenzi 2005; Smith and Leggat 2005). In order to minimise risk factors on health, a safety standard has been formulated (ISO-2361-1 1997). In sports, these rules do not exist; there is a lack of research in this area even if in some activities such as sailing, surfing, skiing, skating and biking, important vibrations occur. Potential dangers should be taken into consideration in sports (Mester et al. 2006). Few studies have tried to establish guidelines and safety standards in order to get benefits from vibration training and to limit the potential dangers. The purpose of this study was to investigate the biodynamic responses using different body positions and various frequencies in order to understand vibration transmissibility in WBVT exercises.

New statistic analysis for BMX rider

BMX racing is an Olympic sport which requires a generation of a high power level (Zabala et al. 2009). This level of power is widely used to evaluate athletes’ explosive power which may be poorly exploited during the race. The explosive muscular power characterise the athlete capacity to increase with a high rate the power output value generated on the pedals. Recently a new powermeter, GCog (Rennen Design Group, Middlesboro, MA, USA), has been developed with a high sampling rate of 250 Hz. Some studies have analysed its reliability (Bertucci et al. 2012; Chiementin et al. 2012). The high sample rate provides a power curve which can characterise athletes. Distribution statistics and the cumulative density function are computed to define the holding time for a percentage of the maximum power and to analyse pacing strategy during sprint.

New performance indicators for BMX riders

BMX racing is an Olympic sport which requires a generation of a high power level (Zabala et al. 2009). This level of power is widely used to evaluate athletes’ explosive power what may be poorly exploited during the race. The explosive muscular power characterises the athlete’s capacity to increase with a high rate the power output value generated on the pedals. A new powermeter, GCOg (Rennen Design Group, Middleboro, MA, USA), has been developed with a high sampling rate of 250 Hz. Some studies have analysed its reliability (Bertucci et al. 2012; Chiementin et al. 2012). Due to this high sampling rate, this study develops new performance indicators to quantify coordination, sequencing and management of the dead centre of the pedalling.

Contribution of Bamboo for Vibratory Comfort in Biomechanics of Cycling

RESEARCH ARTICLE Contribution of Bamboo for Vibratory Comfort in Biomechanics of Cycling Xavier Chiementin, Samuel Crequy, Robin Feron, Marcela Munera, Ellie Abdi, Thomas Provot and Redha Taiar GRESPI, Moulin de la Housse, Université de Reims Champagne Ardenne, Reims, France IN’BO, ZA Les Bouleaux, Les Voivres, France Escuela Colombiana de Ingeniería Julio Garavito, Bogotá D.C., Colombia Montclair State University, Upper Montclair, New Jersey, USA EPF, 3 bis rue Lakanal, Sceaux, France Arts et Métiers ParisTech, MSMP / EA7350, Châlons-en-Champagne, France

Experimental protocol for the risk assessment in cycling

In the world of cycling, vibrations generate back (Hill et al. 2009) and hand–arm system injuries (Schwellnus and Derman 2005) resulting from the trauma of bones, causing work disability. At the same time, pain perception is a source of diminution of performance (Nelson 2003). For these reasons, it is interesting for the bicycle industry to investigate the vibrational behaviour of bicycles and to make an effort to optimise it. This study proposes an experimental protocol to assess vibration transmissions and risks generated in cycling, based on the following standards: ISO-5349-1 2001, ISO-2631-1 1997 and European directive EC/2002 (Directive 2002/44/EC 2002). The protocol assesses bicycle response under periodic excitation effects, distinguishing the front and rear wheel excitation. This study consists of two points: (i) description of the protocol and calculated parameters and (ii) the sensibility and protocol relevance determined by a comparison of two bicycles.