Paraspinal muscle fatigability during various trunk extension tests has been widely investigated by electromyography (EMG), and its task-dependency is established recently. Hip extensor muscle fatigability during the Sorensen test has been reported. The aim of the present experiments was to evaluate the task-dependency of back and hip extensor muscle fatigue during two variants of the Sorensen test. We hypothesized that the rate of muscular fatigue of the hip and back extensor muscles varies according to the test position. Twenty healthy young males with no history of low back pain volunteered to participate in this cross-sectional study. They were asked to perform two body weight-dependent isometric back extension tests (S1 = Sorensen test; S2 = modified Sorensen on a 45 degrees Roman chair). Surface EMG activity of the paraspinal muscles (T10 and L5 levels) and hip extensor muscles (gluteus maximus; biceps femoris) was recorded, and muscular fatigue was assessed through power spectral analysis of the EMG data by calculating the rate of median power frequency change. We observed hip extensor muscle fatigue simultaneously with paraspinal muscle fatigue during both Sorensen variants. However, only L5 level EMG fatigue indices showed a task-dependency effect between S1 and S2. Hip extensor muscles appear to contribute to load sharing of the upper body mass during both Sorensen variants, but to a different extent because L5 level fatigue differs between the Sorensen variants. Our findings suggest that task-dependency has to be considered when EMG variables are compared between two types of lumbar muscle-fatiguing tasks.

译文

肌电图 (EMG) 已广泛研究了各种躯干伸展测试过程中的脊柱旁肌肉疲劳能力,并且最近建立了其任务依赖性。已经报道了Sorensen测试期间的髋伸肌易疲劳性。本实验的目的是评估Sorensen测试的两个变体中背部和髋部伸肌乏力的任务依赖性。我们假设髋部和背部伸肌的肌肉乏力率根据测试位置而变化。20名没有腰痛病史的健康年轻男性自愿参加了这项横断面研究。他们被要求进行两次体重相关的等距背部伸展测试 (S1 = Sorensen测试; S2 = 在45度罗马椅上修改后的Sorensen)。记录椎旁肌 (T10和L5水平) 和髋伸肌 (臀大肌; 股二头肌) 的表面EMG活动,并通过计算中值功率频率变化率,通过EMG数据的功率谱分析评估肌肉乏力。在两个Sorensen变体中,我们同时观察到了髋关节伸肌乏力和椎旁肌乏力。但是,只有L5级EMG乏力指数在S1和s2之间显示出任务依赖性效应。在两个Sorensen变体中,髋关节伸肌似乎都有助于上半身质量的负荷分担,但程度不同,因为Sorensen变体之间的L5水平乏力有所不同。我们的发现表明,在比较两种类型的腰肌疲劳任务之间的EMG变量时,必须考虑任务依赖性。

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