## 1 Introduction  
Every day, the human body is exposed to vibrations, whether during work, transport or sports. Two modes of exposition can be distinguished: whole body vibration and local vibration. Whole body vibrations may have some beneficial effects including ossification [1, 2] and treatment of child muscular disabilities [3]. However, their negative effects have also been proven. Vibration could lead to an accelerated degeneration of joints [4] and vascular diseases [5]. Likewise, local vibrations produce beneficial effects, in sports training for example [6], as well as significant drawbacks, especially in the hand-arm system. Related symptoms can be split into four groups: vascular effects, muscular effects, skeletal effects and joints effects [7], including [PERSON]'s disease [8]. All of them are generally referred to as Hand Arm Vibration Syndrome (HAVS) [9].  
Investigating the effects of vibrations leads us to consider the human body as an extremely complex system, if only because of its responses to vibrations. It is a non-uniform, nonlinear and anisotropic structure. Nevertheless, simplified numerical models, like Finite Elements (FE) models, have been used to study the human body on various aspects: evaluate the injury risk of the lumbar vertebra of a seated human body submitted to vibrations [10] or predict the strains and strength of human femora [11]. A recent study featuring a two-dimensional FE model of the human hand-arm system was also used to estimate significant modal frequencies [12]. These frequencies were then compared to experimental results in order to update the mechanical properties of the model. The study concluded that FE models could be used to obtain reliable resonance frequencies of the human hand-arm system.  
In order to update and validate numerical models, it is necessary to carry out experimental measurements. In this study, Operational Modal Analysis (OMA) is used. The OMA represents the set of modal identification methods based on the sole measurement of the system's response. It has been successfully used in various studies on the human body, mostly for whole body vibrations. Indeed, one of the main fields of interest of modal analysis in this scope is related to transport, including the effects of cabin vibrations [13] or the resonance behavior of the seated human body [14]. OMA and finite elements have already been used jointly to determine modal frequencies, damping and mode shapes, but only on a given part of the human body, e.g., the tibia [15]. Moreover, most of the studies about vibrations and the human body only focus on the hand-arm system: the upper limbs are indeed frequently exposed, for example during biking [16]. However, lower limbs should be given proper attention, as well, since many everyday activities expose legs to vibrations. Solicitations could be similar to white noise in public transport [17] or similar to shock in walking and running activities [18; 19]. Therefore, we have chosen to focus our study on the lower limbs, combining OMA and finite elements on a different scale, i.e., the half-body.  
The aim of this study is to identify the experimental modal parameters of the human lower limbs and to propose an updated two-dimensional finite element model. Experimental modal parameters were extracted by operational modal analysis using poly-reference implementation of a Least Squares Complex Frequency domain (p-LSCF) method.