Hu Xiao, Pickle Nathaniel T, Grabowski Alena M, Silverman Anne K, Blemker Silvia S
Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, United States.
Department of Mechanical Engineering, Colorado School of Mines, Golden, CO, United States.
Front Bioeng Biotechnol. 2020 Oct 14;8:573666. doi: 10.3389/fbioe.2020.573666. eCollection 2020.
In Duchenne muscular dystrophy (DMD), one of the most severe and frequent genetic diseases in humans, dystrophic muscles are prone to damage caused by mechanical stresses during eccentric contractions. Eccentric contraction during walking on level ground likely contributes to the progression of degeneration in lower limb muscles. However, little is known about how the amount of muscle eccentric contractions is affected by uphill/downhill sloped walking, which is often encountered in patients' daily lives and poses different biomechanical demands than level walking. By recreating the dynamic musculoskeletal simulations of downhill (-9°, -6°, and -3°), uphill (+3°, +6°, and +9°) and level walking (0°) from a published study of healthy participants, negative muscle mechanical work, as a measure of eccentric contraction, of 35 lower limb muscles was quantified and compared. Our results indicated that downhill walking overall induced more (32% at -9°, 19% at -6°, and 13% at -3°) eccentric contractions in lower limb muscles compared to level walking. In contrast, uphill walking led to eccentric contractions similar to level walking at low grades (+3° and +6°), but 17% more eccentric contraction at high grades (+9°). The changes of muscle eccentric contraction were largely predicted by the changes in both joint negative work and muscle coactivation in sloped walking. As muscle eccentric contractions play a critical role in the disease progression in DMD, this study provides an important baseline for future studies to safely improve rehabilitation strategies and exercise management for patients with DMD and other similar conditions.
在杜兴氏肌肉营养不良症（DMD）中，这是人类最严重且最常见的遗传疾病之一，营养不良的肌肉在离心收缩过程中容易受到机械应力造成的损伤。在平地上行走时的离心收缩可能会促使下肢肌肉退化的进展。然而，对于上坡/下坡行走如何影响肌肉离心收缩的量，人们知之甚少，而上坡/下坡行走在患者日常生活中经常遇到，并且与平路行走相比会带来不同的生物力学需求。通过重现一项针对健康参与者的已发表研究中的下坡（-9°、-6°和-3°）、上坡（+3°、+6°和+9°）和平路行走（0°）的动态肌肉骨骼模拟，对35条下肢肌肉的负肌肉机械功（作为离心收缩的一种度量）进行了量化和比较。我们的结果表明，与平路行走相比，下坡行走总体上会使下肢肌肉产生更多的离心收缩（-9°时增加32%，-6°时增加19%，-3°时增加13%）。相比之下，上坡行走在低坡度（+3°和+6°）时导致的离心收缩与平路行走相似，但在高坡度（+9°）时离心收缩增加17%。肌肉离心收缩的变化在很大程度上由斜坡行走时关节负功和肌肉共同激活的变化所预测。由于肌肉离心收缩在DMD的疾病进展中起关键作用，本研究为未来研究安全改进DMD患者及其他类似病症患者的康复策略和运动管理提供了重要的基线。
