不同阻力对自行车坐位与立位骑行的影响

Effects of the Different Resistance on Seated and Standing Cycling

在自行车骑行过程中采用坐位或立位均会受到不同阻力的影响，本研究旨在探讨坐位与立位骑行在不同阻力情况下踏板受力与下肢肌电图参数的变化。本研究中，16名受试者分别采用坐位和立位两种姿势进行固定式脚踏车骑行，并比较在低、中、高3种不同阻力情况下的差异。通过力量感测器和表面肌电图获取受试者右脚的数据，并分析踏板受力峰值和冲量，股直肌和股二头肌肌电图峰值及积分肌电图参数。阻力的界定使用固定式脚踏车上的刹车机制，全部测试的踩踏节奏统一为50r／min，统计方法采用多因素方差分析。研究显示，坐位的踏板受力峰值、冲量、肌电图参数受到阻力的影响后呈现上升趋势，而立位的趋势则较不一致。低阻力和中阻力时的踏板受力峰值及冲量是立位大于坐位，而高阻力时则会相接近。再对照肌电图参数，低阻力时是坐位小于立位，中阻力和高阻力时是坐位大于立位。整体而言，阻力较低时是坐位较省力，因为立位的肌肉负担较大；阻力较高时是立位较有效率，因为立位时体重重力可以帮助踩踏。

The use of seated or standing position during cycling is affected by different resistances, the purpose of this study was to investigate the pedal force and electromyography （EMG） with two riding postures （seated and standing） in three levels of resistances （low, middle and high）. In this study, 16 subjects used seated and standing postures for fixed-type bicycle riding, and the differences in low, medium and high three different resistance situations were compared. The data from right leg was acquired by using a force sensor mounted on the right pedal and surface EMG. The parameters, including peak pedal force, impulse, peak EMG and integrated EMG were analyzed. Resistance was defined by the mechanism of brake from stationary bike and pedaling cadence was restricted to 50 r/min in all trials. Multi-way ANOVA was used to detect the significant differences. Our results showed that as resistance increased, seated posture displayed an increased trend in pedal, force, impulse, EMG. However, the trend of standing posture was different compared to seated posture. Standing posture showed higher pedal force and impulse than seated posture at low and middle resistances, but pedal force and impulse of both postures were close to each other at high resistance. Further contrasting with EMG data, standing posture was higher than seated posture at low resistance, but standing posture displayed a smaller activation compared to seated posture at middle and high resistance. In general, seated posture could save strength at light resistance because of less muscle loading than standing posture. However, at heavy resistance, standing posture had better efficiency than seated posture, because cyclist could ride more unhindered by body weight from standing posture.