Department of Sport Science and Kinesiology, University of Salzburg, Austria.
Med Sci Sports Exerc. 2010 Aug;42(8):1545-56. doi: 10.1249/MSS.0b013e3181d299cf.
Since the introduction of carving skis, muscle activity has been investigated primarily on expert-level skiers with respect to EMG intensities. The three-part aim of this recreational skiing study was to analyze functional differences within the quadriceps muscle, to analyze the topographical influence, and to apply a time-frequency analysis of the EMG intensities using wavelets.
Seven female subjects performed two runs through a standardized corridor on a slope with different inclinations (13 degrees , 29 degrees , and 21 degrees ). Knee angle and EMG of vastus lateralis (VL) and rectus femoris (RF) of the right leg were measured during the runs. The recorded EMG signal was resolved with a set of 10 wavelets (11-432 Hz) into a time-frequency space. Subsequently, the EMG intensity and mean frequency (MF) were calculated for different time windows (inside leg; outside leg).
For RF, a significantly higher MF (+15.5%, P = 0.009) but similar EMG intensities were detected in the inside leg compared with the outside leg. For VL, the MF (-9.6%, P = 0.053) and EMG intensities (-54.3%, P = 0.010) were lower in the inside leg compared with the outside leg. Both muscles responded with higher EMG intensities on increasing slope inclination (VL = 90.8%, P = 0.022; RF = 115%, P = 0.01). MF is not directly related to inclination.
Contrary to previously suggested coloading of the inside leg while carving, our results do not support this hypothesis for VL. However, the functional demand for RF in the inside leg is very high when skiing recreationally. The ability of a situation-dependent loading (RF as knee extensor) and unloading (RF as hip flexor) of the inside leg seems to be a crucial point with respect to specific fatigue during a skiing day.
自从引入刻滑技术以来，人们主要针对专家级滑雪者的肌电强度对滑雪时的肌肉活动进行了研究。本项休闲滑雪研究的三个目的是：分析股四头肌的功能差异，分析地形影响，并应用小波对肌电强度进行时频分析。
7 名女性受试者在不同坡度（13°、29°和 21°）的斜坡上的标准通道上进行了两次滑行。在滑行过程中，测量了右膝角度和股外侧肌（VL）和股直肌（RF）的肌电图。记录的肌电图信号通过一组 10 个小波（11-432 Hz）分解到时频空间。随后，在不同的时间窗口（内侧腿；外侧腿）计算肌电强度和平均频率（MF）。
对于 RF，内侧腿的 MF（+15.5%，P=0.009）明显高于外侧腿，但肌电强度相似。对于 VL，内侧腿的 MF（-9.6%，P=0.053）和肌电强度（-54.3%，P=0.010）均低于外侧腿。随着坡度倾斜度的增加，两条肌肉的肌电强度均升高（VL=90.8%，P=0.022；RF=115%，P=0.01）。MF 与坡度倾斜度没有直接关系。
与之前提出的内侧腿在刻滑时会承受更大的负荷的假设相反，我们的结果并不支持这一假设。然而，RF 在休闲滑雪时对内侧腿的功能性需求非常高。内侧腿在特定情况下的受力（RF 作为膝关节伸展肌）和卸力（RF 作为髋关节屈肌）的能力似乎是滑雪日中特定疲劳的关键因素。
