Trunk extensor endurance: determination and relation to low-back trouble

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Abstract
The strength and endurance of the trunk extensors were studied in relation to the extent of earlier low-back trouble (LBT) in a homogeneous, and occupationally active group consisting of 53 male postmen (occupational seniority > 2 years). The isometric endurance was measured (1) prone with the unsupported trunk in a horizontal position and the legs and hips fixated to a couch (couch method) and (2) standing, at 60% MVC (pulling test). The participants were divided into three groups according to the extent of previous LBT Group I, LBT to a degree that made work impossible; Group II, LBT experienced but not to the degree that work was hindered, and Group HI, LBT never experienced. The main findings were that isometric endurance time of the trunk extensors was shorter in Group I than in Groups II and III, while the strength of the trunk extensors was independent of the person's earlier low-back episodes The two methods for the determination of trunk extensor endurance were compared. It was shown that Method 2 is preferable to Method 1, not least in the field of ergonomics. Method 2 is easily practicable and does not demand expensive or complicated equipment. Furthermore this method gives reliable results suitable for statistical preparation and is not influenced by anthropometric factors.