## 1 Introduction  
Road cycling is one of the world's most popular sporting events [1]. Cycling with a steady cadence and appropriate endurance also can be a suitable rehabilitation exercise for patients with an anterior cruciate ligament injury [2]. Cycling is assumed to have a low impact on the body, but cyclists still suffer from a considerable number of overuse injuries. The repetitive nature of the lower extremity during pedaling, and much time spent on training and matches, is one of the main reasons for cyclist overuse injuries [3]. The most common injuries in cyclists occur in the neck (48%) and knee (41.7%) [4].  
Researchers report that many factors such as changes in cadence, body position and direction, saddle height, and fatigue can affect the mechanics of pedaling [5, 6]. Moreover, cycling competition and exercises are performed in different workloads that may alter the kinematics of the joints and segments. Two studies, for instance, focused on the relationship between workload intensity and 3D kinematics in cycling that demonstrated a small-to-moderate difference in lateral spine inclination and spine rotation between recreational and competitive cyclists [6], and an increased joint ranges of motion (ROM) with increasing intensity [7]. Thus, it is beneficial for clinicians and bike fitters to understand how the full-body kinematics and lower limb muscles are affected by differing intensities encountered in cycling training and racing.  
Several studies focus on joint and segment kinematics during cycling, and the majority of these studies have used linear analysis methods by considering the kinematics of individual joints rather than addressing the interactions between joints [6; 7; 8; 9; 10; 11; 12; 13]. However, the motion of segments subsequently influence each other in a kinematic chain [14], as nonlinear dynamic analysis methods, such as the coordination pattern of joints or segments, recently have suggested to provide a better understanding of the biomechanics of human movement and effectively capture the complexity of the coordinated motion of components of the body [15; 16; 17].  
Human body segments are mechanically linked by joints; therefore, the motion of one segment can be affected by the motion of other segments in the same kinetic chain. Therefore, research has suggested using a dynamical system approach in human movement analyses, rather than looking at the kinematics of a single joint [17; 18; 19]. Quantifying kinematic coordination is a tool to determine coupled movements between two segments, and coordination variability (CV) quantifies the variety of movement patterns that an individual uses during a task and can provide a measure of the flexibility/adaptability of an individual's motor system [20; 21]. Thus, a comprehensive approach for investigating segment movement coordination and CV during different pedaling rates is necessary to understand the relation between the pedaling rate and lower extremity biomechanics. The aim of this study is to compare lower limb segment coordination and their variability in cyclists during pedaling at different intensities. We hypothesize that (1) Segment ranges of motion increase with an increase in pedaling intensity, (2) lower extremity intra-segment coordination changes with an increase in pedaling intensity and (3) lower extremity intra-segment coordination variabilities decrease with an increase in pedaling intensity.