Marcela Munera

Transmission of whole body vibration to the lower body in static and dynamic half-squat exercises

Abstract Whole body vibration (WBV) is used as a training method but its physical risk is not yet clear. Hence, the aim of this study is to assess the exposure to WBV by a measure of acceleration at the lower limb under dynamic and static postural conditions. The hypothesis of this paper is that this assessment is influenced by the frequency, position, and movement of the body. Fifteen healthy males are exposed to vertical sinusoidal vibration at different frequencies (20–60 Hz), while adopting three different static postures (knee extension angle: 180°, 120° and 90°) or performing a dynamic half-squat exercise. Accelerations at input source and at three joints of the lower limb (ankle, knee, and hip) are measured using skin-mounted accelerometers. Acceleration values (g) in static conditions show a decrease in the vibrational dose when it is measured at a more proximal location in the lower extremity. The results of the performed statistical test show statistically significant differences (p < 0.05) in the transmissibility values caused by the frequency, the position, and to the presence of the movement and its direction at the different conditions. The results confirm the initial hypothesis and justify the importance of a vibration assessment in dynamic conditions.

Model of the risk assessment of hand-arm system vibrations in cycling: Case of cobblestone road

Vibrations experienced by the human body are a well-known and widely studied risk factor in the industrial world. These are transmitted to the whole body or parts of it (like the hand-arm system) and are measured and limited according to international standards and European directives. However, despite the ubiquity of vibrations, their effects are little studied in sport. Vibrations can induce discomfort, thus degrading performance, or even cause musculoskeletal disorders. This article presents a numerical methodology to estimate the vibration total value transmitted to the hand-arm system during the practice of cycling over cobblestone roads. This assessment is achieved using a modeling of the excitation source representing the displacement over the cobblestone, as well as the vibratory behavior of the cycle. The influence of the model parameters will be discussed. Finally, the estimated vibration total value will be compared to values obtained from field test conditions.

Analysis of muscular activity and dynamic response of the lower limb adding vibration to cycling

ABSTRACT Vibration in cycling has been proved to have undesirable effects over health, comfort and performance of the rider. In this study, 15 participants performed eight 6-min sub-maximal pedalling exercises at a constant power output (150W) and pedalling cadence (80 RPM) being exposed to vibration at different frequencies (20, 30, 40, 50, 60, 70 Hz) or without vibration. Oxygen uptake (VO2), heart rate (HR), surface EMG activity of seven lower limb muscles (GMax, RF, BF, VM, GAS, SOL and TA) and 3-dimentional accelerations at ankle, knee and hip were measured during the exercises. To analyse the dynamic response, the influence of the pedalling movement was taken into account. The results show that there was not significant influence of vibrations on HR and VO2 during this pedalling exercise. However, muscular activity presents a significant increase with the presence of vibration that is influenced by the frequency, but this increase was very low (< 1%). Also, the dynamic response shows an influence of the frequency as well as an influence of the different parts of the pedalling cycle. Those results help to explain the effects of vibration on the human body and the influence of the rider/bike interaction in those effects.

Effect of vibration frequency and angle knee flexion on muscular activity and transmissibility function during static whole body vibration exercise.

Whole bodyvibrations (WBV) created by the useof vibrating platform exercise were largely studied for their impact on muscular activity, neuromuscular and postural control (Fratini et al. 2009). Lower limb muscle response to vibration depends on static body position, muscle stiffness, amplitude and frequency of the mechanical vibration (Pollock et al. 2010). Nevertheless, the effect of body position and frequency of vibration on electromyography (EMG) signal are still discussed as several previous studies reported muscular activity increase (Fratini et al. 2009; Pollock et al. 2010; Giminiani et al. 2013), whereas recent studies indicate no significant variation in EMG activity (Avelar et al. 2013). These differences could be due to the vibrations parameters, i.e. amplitude (1–5mm) and frequency (5–55Hz), the degree of knee flexion (5–908) used and the muscle studied. Moreover, most of the time, these studies used closed chain configuration since subjects hold bodypositiononvibratingplatformswithhandsgraspingona front support. The aim of this study was to study the response of lower limb tissues to varied vibration frequencies and angle knee flexion during static body position by measuring thigh and leg muscles activity and the transmissibility function of input vibration across lower body joints.

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

Footwear influences soft-tissue vibrations in rearfoot strike runners

Figure 1 shows the peak magnitude of the high frequency component of the vertical GRF, per foot zone (fore-foot, mid-foot, lateral and medial rear-foot and merged rearfoot zones) for the different foot strike patterns. The highest peak values were found under the rearand mid-foot zone for the Typical RFS, under the mid-foot zone for the Atypical RF and under the midand fore-foot zone for the MFS.

Transmission of whole-body vibration to lower limb during dynamic squat exercise

Whole-body vibration (WBV) exercise has been used for several years to improve neuromuscular performance in athletes or patients. One parameter measured to study the response of the human body to vibration is the transmissibility function. Transmissibility can be determined from the ratio of forces, displacements, velocities or accelerations. Several studies have measured the transmissibility of input vibration delivered by a platform in a standing or flexed position (Avelar et al. 2013) and using different frequencies (Kiiski et al. 2008) and/or amplitudes (Pollock et al. 2010). The majority of these studies have been conducted in a static position. To the best of our knowledge there are no studies that evaluate this physical risk with movement. If movement and vibration exposure are present at the same time, it could be assumed that the movement affects the transmitted dose of vibration throughout the human joints. This could be because movement is a continuous change of position in the human body and it also changes the absorption of energy in the involved segments. So, the aim of this work was to measure the vibration transmissibility (T) according to (1) the movement represented as the relative angle between the segments (u) and its direction, and (2) to measure the excitation frequency of the vibration (v).

Mechanical equivalent model of vibration transmission in cycling

The vibration is an omnipresent movement, both for mechanical systems and for men (Griffin 1990). These are found in the daily activities, during work and sports. Along with the resonance phenomena, excitatory vibrations may be beneficial or harmful. The effects depend on the vibration characteristics: magnitude, frequency, duration and direction (Griffin 1990). Several studies focused on pathologies and the effects of the vibrations such as Raynaud’s syndrome or carpal tunnel syndrome. In this study, we were interested in the physical risk associated with vibration when cycling. Some studies have evaluated the transmission of the vibrations to the different parts of the human body (Rützel et al. 2006; Peretti et al. 2009; Chiementin et al. 2011). In other studies, the modelling has shown the response behaviour of vibrations in cycling (Rützel et al. 2006; Dong et al. 2007). One of the models used is the mechanical equivalent model, which represents the system with mechanical masses, springs and dampers. In this study, we present the protocol to measure the transmission of vibrations in the front of the bicycle. This transmission was represented with an equivalent mechanical model that shows the transmission of vibrations coming from the road to hand-bike interface. The acceleration obtained with this model was compared to the experimental acceleration in the work of Chiementin et al. (2012).