School of Kinesiology, Auburn University, Auburn, AL, USA.
Department of Physical Education, Federal University of São Carlos, São Carlos, Brazil.
Exp Physiol. 2022 Nov;107(11):1216-1224. doi: 10.1113/EP090666. Epub 2022 Sep 30.
What is the central question of this study? Do changes in myofibre cross-sectional area, pennation angle and fascicle length predict vastus lateralis whole-muscle cross-sectional area changes following resistance training? What is the main finding and its importance? Changes in vastus lateralis mean myofibre cross-sectional area, fascicle length and pennation angle following a period of resistance training did not collectively predict changes in whole-muscle cross-sectional area. Despite the limited sample size in this study, these data reiterate that it remains difficult to generalize the morphological adaptations that predominantly drive tissue-level vastus lateralis muscle hypertrophy.
Myofibre hypertrophy during resistance training (RT) poorly associates with tissue-level surrogates of hypertrophy. However, it is underappreciated that, in pennate muscle, changes in myofibre cross-sectional area (fCSA), fascicle length (L ) and pennation angle (PA) likely coordinate changes in whole-muscle cross-sectional area (mCSA). Therefore, we determined if changes in fCSA, PA and L predicted vastus lateralis (VL) mCSA changes following RT. Thirteen untrained college-aged males (23 ± 4 years old, 25.4 ± 5.2 kg/m ) completed 7 weeks of full-body RT (twice weekly). Right leg VL ultrasound images and biopsies were obtained prior to (PRE) and 72 h following (POST) the last training bout. Regression was used to assess if training-induced changes in mean fCSA, PA and L predicted VL mCSA changes. Correlations were also performed between PRE-to-POST changes in obtained variables. Mean fCSA (+18%), PA (+8%) and mCSA (+22%) increased following RT (P < 0.05), but not L (0.1%, P = 0.772). Changes in fCSA, L and PA did not collectively predict changes in mCSA (R = 0.282, adjusted R = 0.013, F = 1.050, P = 0.422). Moderate negative correlations existed for percentage changes in PA and L (r = -0.548, P = 0.052) and changes in fCSA and L (r = -0.649, P = 0.022), and all other associations were weak (|r| < 0.500). Although increases in mean fCSA, PA and VL mCSA were observed, inter-individual responses for each variable and limitations for each technique make it difficult to generalize the morphological adaptations that predominantly drive tissue-level VL muscle hypertrophy. However, the small subject pool is a significant limitation, and more research in this area is needed.
本研究的核心问题是什么？肌纤维横截面积、肌小节角度和肌束长度的变化是否可以预测阻力训练后股外侧肌整体肌纤维横截面积的变化？主要发现及其重要性是什么？经过一段时间的抗阻训练，股外侧肌的平均肌纤维横截面积、肌束长度和肌小节角度的变化并不能共同预测整个肌肉横截面积的变化。尽管本研究的样本量有限，但这些数据再次表明，很难将主要驱动组织水平股外侧肌肥大的形态适应进行概括。
抗阻训练（RT）期间肌纤维肥大与组织水平肥大的替代物相关性较差。然而，在羽状肌中，肌纤维横截面积（fCSA）、肌束长度（L）和肌小节角度（PA）的变化可能与整个肌肉横截面积（mCSA）的变化协调一致，这一点尚未得到充分认识。因此，我们确定股外侧肌（VL）的 fCSA、PA 和 L 的变化是否可以预测 RT 后 VL mCSA 的变化。13 名未经训练的大学生（23±4 岁，25.4±5.2kg/m2）完成了 7 周的全身 RT（每周 2 次）。在最后一次训练结束后 72 小时（POST）之前，对右侧腿部 VL 进行超声图像和活检。回归用于评估训练诱导的平均 fCSA、PA 和 L 的变化是否可以预测 VL mCSA 的变化。还对获得的变量的 PRE 到 POST 变化之间进行了相关性分析。RT 后，平均 fCSA（增加 18%）、PA（增加 8%）和 mCSA（增加 22%）增加（P<0.05），但 L 没有变化（0.1%，P=0.772）。fCSA、L 和 PA 的变化并没有共同预测 mCSA 的变化（R=0.282，调整后的 R=0.013，F=1.050，P=0.422）。PA 和 L 的百分比变化之间存在中度负相关（r=-0.548，P=0.052），fCSA 和 L 之间的变化存在中度负相关（r=-0.649，P=0.022），而所有其他相关性均较弱（|r|<0.500）。尽管观察到平均 fCSA、PA 和 VL mCSA 的增加，但每个变量的个体反应以及每种技术的局限性使得很难将主要驱动组织水平 VL 肌肉肥大的形态适应进行概括。然而，小的研究对象池是一个显著的局限性，这个领域需要更多的研究。
