Rectus abdominis (RA) and rectus femoris (RF) differently activate in hip and trunk flexion movements. Previous studies using surface electromyography (sEMG) showed heterogenous results in mean and maximum activity of Upper (URA), Middle (MRA), and Lower (LRA) RA. Statistical Parametric Mapping (SPM) and Time-Varying Multi-muscle Co-activation function (TMCf) are emerging methods for whole-time-course continuous comparisons of muscle activity and co-activation. The aim was to analyse RA and RF activity in three core training exercises with continuous approach. Eight subjects performed Curl-up, Sit-up 45° and Sit-up 90° (where 45° is half and 90° is complete trunk flexion). sEMG from URA, MRA, LRA and RF were normalized to the maximum voluntary contraction root-mean-square (RMSMVC), and compared among muscles/exercises with SPM and TMCf. Angular displacement was assessed using stereophotogrammetry. Curl-up, Sit-up 45° and Sit-up 90° did not differently activate URA, MRA or LRA, and in their common range of motion (ROM) RA activity was similar among the three exercises. Conversely, Sit-up exercises elicited higher RF activity than Curl-up (on average 45% vs. 25% RMSMVC) mainly due to the wider ROM. RA-RF co-activation pattern was different in concentric and eccentric phases between Sit-up exercises and Curl-up, leading to significantly higher co-activation in Sit-up exercises.

中文翻译：

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在不同的核心训练中，腹直肌的活动（而不是股骨的活动）相似：统计参数映射分析。

腹直肌（RA）和股直肌（RF）在髋部和躯干屈曲运动中的激活方式不同。先前使用表面肌电图（sEMG）进行的研究显示，上（URA），中（MRA）和下（LRA）RA的平均和最大活性存在异质结果。统计参数映射（SPM）和时变多肌肉共同激活函数（TMCf）是新兴的方法，用于肌肉活动和共同激活的全过程连续比较。目的是通过连续方法分析三项核心训练中的RA和RF活动。八名受试者进行了翘起，仰卧45°和仰卧90°（其中45°是一半，而90°是躯干完全屈曲）。将来自URA，MRA，LRA和RF的sEMG归一化为最大自愿收缩均方根（RMSMVC），并在具有SPM和TMCf的肌肉/运动中进行比较。使用立体摄影测量法评估角位移。翘起，仰卧45°和仰卧90°并没有不同地激活URA，MRA或LRA，并且在它们的共同运动范围（ROM）中，三种锻炼中的RA活动相似。相反，仰卧起坐练习产生的RF活动要比Curl-up高（平均45％vs. 25％RMSMVC），这主要是由于ROM更宽。仰卧起坐运动和卷曲运动之间的同心和偏心阶段，RA-RF共激活模式不同，从而导致仰卧起坐运动的共激活明显更高。仰卧起坐练习产生的射频活动比卷曲仰卧起坐活动高（平均RMSMVC为45％，而RMSMVC为25％），这主要是由于ROM更大。仰卧起坐运动和卷曲运动之间的同心和偏心阶段，RA-RF共激活模式不同，从而导致仰卧起坐运动的共激活明显更高。仰卧起坐练习产生的射频活动比卷曲法（平均45％vs. 25％RMSMVC）高，这主要是由于ROM更大。仰卧起坐运动和卷曲运动之间的同心和偏心阶段，RA-RF共激活模式不同，从而导致仰卧起坐运动的共激活明显更高。