Dingwell Jonathan B, Joubert Jason E, Diefenthaeler Fernando, Trinity Joel D
Department of Kinesiology, University of Texas, Austin, TX 78712, USA.
IEEE Trans Biomed Eng. 2008 Nov;55(11):2666-74. doi: 10.1109/TBME.2008.2001130.
Muscle fatigue may alter kinematics and contribute to repetitive strain injuries. This study quantified how both localized muscle fatigue and movement kinematics change over time during exhaustive cycling. Seven highly trained cyclists rode a stationary bicycle ergometer at 100% of their maximum oxygen consumption (VO(2) max) until voluntary exhaustion. Cycling kinematics and electromyography (EMG) activity from select lower extremity muscles were recorded. Cross-correlations were computed to quantify how EMG median frequencies (MDFs) changed with changes in movement kinematics. All athletes maintained both cadence and power output for approximately 90% of the trial duration. Significant sustained muscle fatigue occurred in 18 of 28 muscles tested, most prominently in the biceps femoris (p = 0.020) and gastrocnemius (p = 0.018). Kinematics and MDF both fluctuated nonmonotonically as subjects fatigued. Changes in MDF significantly preceded changes in mean trunk lean (p = 0.009) and hip angles (p = 0.025), and trunk lean range of motion ( p = 0.029). Fluctuations in MDF were positively correlated with fluctuations in mean trunk lean (p = 0.009) and knee splay angles (p = 0.011), and with trunk lean (p = 0.002) and ankle (p = 0.001) range of motion. These results therefore establish a direct link between changes in muscle fatigue state and subsequent changes in movement kinematics during cycling.
肌肉疲劳可能会改变运动学，并导致重复性劳损。本研究量化了在力竭性骑行过程中，局部肌肉疲劳和运动学如何随时间变化。七名训练有素的自行车运动员以其最大耗氧量（VO₂ max）的100%在固定自行车测力计上骑行，直至自愿力竭。记录了骑行运动学和选定下肢肌肉的肌电图（EMG）活动。计算交叉相关性以量化EMG中位频率（MDF）如何随运动学变化而改变。所有运动员在大约90%的试验持续时间内保持了踏频和功率输出。在测试的28块肌肉中，有18块出现了显著的持续性肌肉疲劳，最明显的是股二头肌（p = 0.020）和腓肠肌（p = 0.018）。随着受试者疲劳，运动学和MDF均呈非单调波动。MDF的变化显著先于平均躯干倾斜度（p = 0.009）和髋关节角度（p = 0.025）以及躯干倾斜度运动范围（p = 0.029）的变化。MDF的波动与平均躯干倾斜度（p = 0.009）和膝关节外展角度（p = 0.011）以及躯干倾斜度（p = 0.002）和踝关节（p = 0.001）运动范围的波动呈正相关。因此，这些结果建立了骑行过程中肌肉疲劳状态变化与随后运动学变化之间的直接联系。
