Korff Thomas, Jensen Jody L
Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, Middlesex UB8 3PH, UK.
Exp Brain Res. 2007 Mar;177(3):291-303. doi: 10.1007/s00221-006-0684-3.
Acquisition of skillfulness is not only characterized by a task-appropriate application of muscular forces but also by the ability to adapt performance to changing task demands. Previous research suggests that there is a different developmental schedule for adaptation at the kinematic compared to the neuro-muscular level. The purpose of this study was to determine how age-related differences in neuro-muscular organization affect the mechanical construction of pedaling at different levels of the task. By quantifying the flow of segmental energy caused by muscles, we determined the muscular synergies that construct the movement outcome across movement speeds. Younger children (5-7 years; n = 11), older children (8-10 years; n = 8), and adults (22-31 years; n = 8) rode a stationary ergometer at five discrete cadences (60, 75, 90, 105, and 120 rpm) at 10% of their individually predicted peak power output. Using a forward dynamics simulation, we determined the muscular contributions to crank power, as well as muscular power delivered to the crank directly and indirectly (through energy absorption and transfer) during the downstroke and the upstroke of the crank cycle. We found significant age x cadence interactions for (1) peak muscular power at the hip joint [Wilks' Lambda = 0.441, F(8,42) = 2.65, p = 0.019] indicating that at high movement speeds children produced less peak power at the hip than adults, (2) muscular power delivered to the crank during the downstroke and the upstroke of the crank cycle [Wilks' Lambda = 0.399, F(8,42) = 3.07, p = 0.009] indicating that children delivered a greater proportion of the power to the crank during the upstroke when compared to adults, (3) hip power contribution to limb power [Wilks' Lambda = 0.454, F(8,42) = 2.54, p = 0.023] indicating a cadence-dependence of age-related differences in the muscular synergy between hip extensors and plantarflexors. The results demonstrate that in spite of a successful performance, children construct the task of pedaling differently when compared to adults, especially when they are pushed to their performance limits. The weaker synergy between hip extensors and plantarflexors suggests that a lack of inter-muscular coordination, rather than muscular power production per se, is a factor that limits children's performance ranges.
熟练技能的获得不仅表现为对肌肉力量进行与任务相适应的运用，还表现为根据任务需求的变化调整动作表现的能力。先前的研究表明，与神经肌肉水平相比，运动学层面的适应具有不同的发展进程。本研究的目的是确定神经肌肉组织中与年龄相关的差异如何在不同任务水平上影响蹬踏动作的力学结构。通过量化肌肉引起的节段能量流动，我们确定了在不同运动速度下构建运动结果的肌肉协同作用。年幼儿童（5 - 7岁；n = 11）、年长儿童（8 - 10岁；n = 8）和成年人（22 - 31岁；n = 8）以各自预测峰值功率输出的10%，在五个离散的踏频（60、75、90、105和120转/分钟）下骑固定测力计。使用正向动力学模拟，我们确定了肌肉对曲柄功率的贡献，以及在曲柄周期的下行和上行过程中直接和间接（通过能量吸收和传递）传递到曲柄的肌肉功率。我们发现存在显著的年龄×踏频交互作用，表现为：（1）髋关节处的峰值肌肉功率[威尔克斯λ = 0.441，F(8,42) = 2.65，p = 0.019]，表明在高运动速度下，儿童在髋关节处产生的峰值功率低于成年人；（2）在曲柄周期的下行和上行过程中传递到曲柄的肌肉功率[威尔克斯λ = 0.399，F(8,42) = 3.07，p = 0.009]，表明与成年人相比，儿童在上行过程中传递到曲柄的功率比例更大；（3）髋关节功率对肢体功率的贡献[威尔克斯λ = 0.454，F(8,42) = 2.54，p = 0.023]，表明髋关节伸肌和跖屈肌之间肌肉协同作用中与年龄相关的差异存在踏频依赖性。结果表明，尽管儿童能够成功完成任务，但与成年人相比，他们在蹬踏任务的构建方式上有所不同，尤其是当他们被推向表现极限时。髋关节伸肌和跖屈肌之间较弱的协同作用表明，肌肉间协调不足而非肌肉力量本身的产生，是限制儿童表现范围的一个因素。
