The Effect Of Saddle Height On Lower Extremity Biomechanics During Cycling

Objective: Adjusting the saddle height should be done for every experienced rider during cycling,because scientific and reasonable saddle height can reduce the risk of overuse injure,improve sports performance,reduce energy consumption and so on.Therefore,the adjustment of saddle height is considered to be the most important cycling assembly adjustment by the rider.At present,there are different methods of how to set saddle height.It is still not known which saddle height can not only prevent injury but also improve sports performance.In the meantime,whether the method in foreign literature is in accordance with the body shape of Chinese is not known as well.Thus the purpose of this study is to analyze the effects of different saddle heights on exercise,dynamics and muscle EMG activity of lower extremities,and hopefully could provide theoretical reference for exploring the best saddle height and provide suggestions for scientific fitness during cycling.Methods: Twenty young ordinary people with cycling habits(23.4 ± 0.5 years)performed 3minutes of cycling at four different saddle heights(Medium [25° knee flexion angle],Preferred [a height chosen by cyclists],Low [Preferred + 15°],High [Preferred-15°] measured at the bottom-dead-center).Cycling workload and cadence were set at 60 w and 60 rpm respectively,since our project was focused on rehabilitation.A motion analysis system,a custom instrumented pedal and an EMG acquisition systems were used to collect three-dimensional kinematics(200Hz),pedal reaction force(1000Hz)and EMG(2000Hz).Results: It showed that,compared with other saddle heights,low saddle height produced greater adduction knee moments(11.9 ± 1.9 Nm,P < 0.05),larger knee flexion(58.5 ± 2.6°,P < 0.05)and larger abduction angles(-4.5 ± 0.8°,P < 0.05),vatsus medialis RMS(p = 0.03),quadriceps femoris force(P = 0.001),patellofemoral joint force(P < 0.001)and the angle of knee joint at the time of peak patellofemoral joint force(P < 0.001).With the increase of saddle height,the mechanical work of knee joint decreased(p < 0.001),the ankle joint increased,but no significant effect on hip joint during the power phase.The mechanical work contribution of the knee increased,the hip decreased,but no significant effect on ankle joint during recover phase.Compared with other saddle heights,high saddle height produced smaller average duration of maximum torque(DATD,P < 0.004),The changing of saddle height affected the RMS of gluteusmaximus(GMax),vatsus medialis(VM),biceps femoris(BF)etc.(p > 0.05);compared with saddle height Low,the duration of activity increased(p < 0.05)for the EMG signal of GMax,ST and BF cycling with saddle height High;RF/GMax had the smallest coactivation cycling with saddle height High,the coactivation of BF/VM,GM/VM medialis increased with the rised of saddle height,and the coactivation of GM/TA was not affected by seaddle height;pedal force decreased when seddle height increased,and effective force was not affected by saddle height.Conclusion:(1)It is showed that Low saddle height resulted in increased knee adduction moments with longer duration.In contrast,High saddle height reduced both knee moments and time duration.The result suggests that increased saddle heights may provide a safe and efficient cycling strategy for ordinary people with cycling habits.(2)Comparing to higher saddle height during cycling,a low saddle height produced greater peak quadriceps force,patellofemoral joint force,patellofemoral joint stress,and greater knee angle shown at the peak of the patellofemoral joint force.These results suggest that cycling with a low saddle height may have a negative impact on patellofemoral joints.(3)The intensity and duration of some lower limbs muscle activity increased cycling with the high saddle heights at constant power,which lead to the decrease of VM activity and the coactivation of RF/Gmax,and may be the reason of the decreased pedal force.Thus,it is not recommended to cycling with over high saddle height.