Human Movement Biomechanics Research Group, Department of Kinesiology, KU Leuven, Leuven , Belgium.
Movement Laboratory, Department of Sport Science, Stellenbosch University, Stellenbosch, Western Cape, South Africa.
J Appl Physiol (1985). 2018 Feb 1;124(2):462-472. doi: 10.1152/japplphysiol.00429.2017. Epub 2017 Jul 27.
Maintaining stability under dynamic conditions is an inherent challenge to bipedal running. This challenge may impose an energetic cost (Ec) thus hampering endurance running performance, yet the underlying mechanisms are not clear. Wireless triaxial trunk accelerometry is a simple tool that could be used to unobtrusively evaluate these mechanisms. Here, we test a cost of instability hypothesis by examining the contribution of trunk accelerometry-based measures (triaxial root mean square, step and stride regularity, and sample entropy) to interindividual variance in Ec (J/m) during treadmill running. Accelerometry and indirect calorimetry data were collected concurrently from 30 recreational runners (16 men; 14 women) running at their highest steady-state running speed (80.65 ± 5.99% V̇o). After reducing dimensionality with factor analysis, the effect of dynamic stability features on Ec was evaluated using hierarchical multiple regression analysis. Three accelerometry-based measures could explain an additional 10.4% of interindividual variance in Ec after controlling for body mass, attributed to anteroposterior stride regularity (5.2%), anteroposterior root mean square ratio (3.2%), and mediolateral sample entropy (2.0%). Our results lend support to a cost of instability hypothesis, with trunk acceleration waveform signals that are 1) more consistent between strides anteroposterioly, 2) larger in amplitude variability anteroposterioly, and 3) more complex mediolaterally and are energetically advantageous to endurance running performance. This study shows that wearable trunk accelerometry is a useful tool for understanding the Ec of running and that running stability is important for economy in recreational runners. NEW & NOTEWORTHY This study evaluates and more directly lends support to a cost of instability hypothesis between runners. Moreover, this hypothesis was tested using a minimalist setup including a single triaxial trunk mounted accelerometer, with potential transferability to biomechanical and performance analyses in typical outdoor settings.
在动态条件下保持稳定是双足奔跑固有的挑战。这种挑战可能会带来能量成本（Ec），从而阻碍耐力奔跑表现，但潜在机制尚不清楚。无线三轴躯干加速度计是一种简单的工具，可以用来非侵入性地评估这些机制。在这里，我们通过检查基于躯干加速度计的测量值（三轴均方根、步和步幅的规律性以及样本熵）对 Ec（J/m）个体间变异性的贡献来检验不稳定性成本假设，在跑步机跑步过程中。加速度计和间接测热法数据同时从 30 名休闲跑步者（16 名男性；14 名女性）在最高稳态跑步速度（80.65±5.99%Vo）下收集。在通过因子分析降低维度后，使用分层多元回归分析评估动态稳定性特征对 Ec 的影响。在控制体重后，基于加速度计的三个测量值可以解释 Ec 个体间变异性的另外 10.4%，这归因于前后步的规律性（5.2%）、前后均方根比（3.2%）和左右样本熵（2.0%）。我们的结果支持不稳定性成本假设，即躯干加速度波信号在 1）前后步之间更一致，2）前后振幅变化更大，3）左右更复杂，在能量上有利于耐力奔跑表现。这项研究表明，可穿戴式躯干加速度计是理解 Ec 奔跑的有用工具，并且奔跑稳定性对于休闲跑步者的经济性很重要。 本研究评估并更直接地支持了跑步者之间的不稳定性成本假设。此外，该假设是使用包括单个三轴躯干安装加速度计的最小化设置进行测试的，具有在典型户外环境中向生物力学和性能分析转移的潜力。
