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How saddle height changes the hip kinematics pattern in different degree of freedom

2023; Elsevier BV; Volume: 106; Linguagem: Inglês

10.1016/j.gaitpost.2023.07.029

1879-2219

Alireza Zohari, Taraneh Salehsari, Hamidreza Barnamehei,

Sports injuries and prevention

The cycling is common sport that people do that for entertainment and matches. The hip joint play key role to transfer energy from core of body to cranks [1]. In addition, kinematics changes in hip joint effect on knee and ankle joints. One of the fundamental factors of bicycle variables is saddle heights that was manipulated based on anthropometric characteristics [2]. The question remains how athletes choose the best saddle height [3]. Therefore, the aim of the current attempt was to compare three degrees of freedom (DOF) of hip for two different saddles during cycling. How different DOF of hip play their roles in two different saddles during cycling? Twenty professional athletes participated in this study (Mass: 75.3±6.5 kg, Heights: 180±6.3 cm, Age: 28.5±6.5 years). Ten Vicon motion captures (Vicon MX, Oxford, UK, 100 Hz) were utilized to record the markers positions [4]–[6]. The smart trainer (Tacx Flux, Netherland) was used to measure output power of bicycle. The inseam quantity (the distance from the uppermost of part of thigh to ankle) of each subject measured and then multiply to 0.883 to find standard saddle height that was choose as lower saddle. Then, we added the 4% to lower saddle height that was choose as upper saddle. The cadence remains at 60 rpm for times of cycling. The full body model used as base model in OpenSim [7]. The personalized model created for each subject by scaling tool. The joint angles were calculated by inverse kinematics tool in OpenSim [8]–[9]. The Fig. 1 represents the mean and standard deviation of three DOF of hip joint for two different saddle heights during the cycling. The significant differences of hip angles between lower and upper saddle were found in hip rotation (p<0.05). Furthermore, maximum variability was observed in hip rotation for upper saddle. Download : Download high-res image (166KB)Download : Download full-size image Fig. 1. Mean and standard deviation of three DOF of hip joint for two different saddle heights during the cycling with respect to angle of crank angle. This study is basic attempt that compared two different saddle height. According to the results, the main effect of saddle heights is on the hip rotation, therefore the role of rotator muscles of hip will be highlighted. Furthermore, the maximum variability of the hip rotation in lower saddle height indicates athletes in lower saddle condition didn't use stable motor control strategy. The main limitation of this study was we only used two saddle heights. All coaches, athletes, and scientist in various levels can used these results to find best height of saddle based on hip kinematics.