Department of Training and Movement Sciences, Humboldt-Universität zu Berlin, Philippstr. 13, Haus 11, 10115, Berlin, Germany.
Sci Rep. 2023 May 29;13(1):8661. doi: 10.1038/s41598-023-35441-9.
Tendon strain during exercise is a critical regulatory factor in tendon adaptive responses and there are indications for an optimal range of strain that promotes tendon adaptation. Back squats are used to improve patellar tendon properties in sport and clinical settings. To date, the operating patellar tendon strain during back squats is unknown and current recommendations for individual exercise loading are based on the one repetition maximum (1RM). Here, we quantified patellar tendon strain during loaded back squats at 40, 60 and 80% of the 1RM and during maximum isometric knee extension contractions (MVC) using ultrasonography. Kinematics, ground reaction forces and muscle electromyographic activity were also recorded. Additionally, maximum tendon strain during the MVC and the percentage of 1RM were used as explanatory variables to estimate the individual patellar tendon strain during the squats. Strain increased with increasing 1RM loading (4.7 to 8.2%), indicating that already medium-loading back squats may provide a sufficient stimulus for tendon adaptation. The individual variability was, however, too high to generalize these findings. Yet, there was a high agreement between the individually estimated and measured patellar tendon strain (R = 0.858) during back squats. We argue that this approach may provide new opportunities for personalized tendon exercise.
运动过程中的肌腱应变是肌腱适应反应的一个关键调节因素，有迹象表明存在一个促进肌腱适应的最佳应变范围。后深蹲用于改善运动和临床环境中的髌腱特性。迄今为止，后深蹲过程中髌腱的实际应变情况尚不清楚，目前针对个体运动负荷的建议是基于最大重复次数（1RM）。在这里，我们使用超声测量了在 1RM 的 40%、60%和 80%负荷下以及在最大等长膝关节伸展收缩（MVC）期间的髌腱应变。运动学、地面反作用力和肌肉肌电图活动也被记录下来。此外，还将 MVC 期间的最大肌腱应变和 1RM 的百分比用作解释变量，以估计深蹲过程中的个体髌腱应变。应变随着 1RM 负荷的增加而增加（4.7%至 8.2%），表明中等负荷的后深蹲可能已经为肌腱适应提供了足够的刺激。然而，个体的变异性太高，无法推广这些发现。然而，在后深蹲过程中，个体估计和测量的髌腱应变之间具有高度的一致性（R=0.858）。我们认为，这种方法可能为个性化肌腱运动提供新的机会。
