CeRiSM (Research Center Sport Mountain & Health), Via Matteo del Ben 5/b, 38068, Rovereto, Italy.
Neuroscience, Biomedicine and Movement Science Department, University of Verona, Verona, Italy.
Eur J Appl Physiol. 2017 Nov;117(11):2149-2157. doi: 10.1007/s00421-017-3703-0. Epub 2017 Aug 24.
To evaluate the level of activation and timing of upper- and lower-body muscles during double poling at different speeds on snow.
Nineteen well-trained cross-country skiers volunteered to double pole on a flat snowy track at different speeds (15, 18, 21 km h). The target speeds could be maintained by the skiers thanks to the use of an audio-pace system in combination with cones spaced equally alongside the track. Only 11 subjects were finally included in the analysis, since their actual speeds, calculated through a photocell system, were within ±0.5 km h from those requested. Cycle and poling durations were measured from the recordings of an accelerometer attached to a wrist, while the pattern and the level of muscle activation were evaluated from electromyographyc signals.
Double poling speed did not alter the sequence of muscle activation that started with hip flexors, continued with trunk flexors, shoulder, elbow and trunk extensors and ended with ankle plantar-flexors. However, higher speeds required an increasing involvement of thigh, trunk and shoulder muscles (P < 0.05) as well as an anticipation of their activation before pole plant (P < 0.05).
A progressively earlier activation of trunk and lower limb muscles is a coordinative strategy that allows rapid achievement of optimal body posture prior to the exertion of poling phase. Moreover, earlier activation of these muscles as the speed increases provides adequate muscle stiffness in the shoulder and core regions for the acceptance of the poling load.
评估在雪地上以不同速度双杖支撑时，上下肢肌肉的激活水平和时序。
19 名训练有素的越野滑雪运动员在平坦的雪道上以不同速度（15、18、21 公里/小时）进行双杖支撑。由于使用音频节拍系统与沿着轨道等距设置的锥形障碍物相结合，运动员可以维持目标速度。只有 11 名受试者最终被纳入分析，因为他们的实际速度通过光电系统计算，与要求的速度相差±0.5 公里/小时以内。通过附着在手腕上的加速度计的记录来测量周期和撑杆时间，同时通过肌电图信号来评估肌肉激活的模式和水平。
双杖支撑速度并没有改变肌肉激活的顺序，该顺序从髋关节屈肌开始，然后是躯干屈肌、肩部、肘部和躯干伸肌，最后是踝关节跖屈肌。然而，较高的速度需要大腿、躯干和肩部肌肉的参与度增加（P < 0.05），以及在撑杆前提前激活这些肌肉（P < 0.05）。
躯干和下肢肌肉的逐渐提前激活是一种协调策略，允许在进行撑杆阶段之前快速达到最佳身体姿势。此外，随着速度的增加，这些肌肉的提前激活为肩部和核心区域提供了足够的肌肉刚度，以承受撑杆的负荷。
