Abstract
BackgroundBack extension (BE) is a strength exercise for training the dorsal trunk and hip muscles. To optimise training recommendations that avoid overloading and possible injury, the aim of this study was to determine the loading conditions and the influence of different execution forms of BE on spine, hip and knee ranges of motion (RoMs), joint moments and muscle activity.MethodsThe kinematics, kinetics and muscle activity (EMG) of two execution types (BEh: dynamic hip, BEs: dynamic spine) and two versions (one-legged and two-legged) of BE were measured in 16 subjects. RoMs and external joint moments were calculated using an inverse dynamics approach and analysed with a linear mixed model.ResultsAlthough lumbar spine flexion was observed in both execution types, thoracic spine flexion predominantly occurred during BEs, whereas thoracic spine extension was observed during BEh. Larger maximal back and hip moments were observed for BEh than for BEs. The activity of the dorsal back and hip muscles, as observed using EMG, was increased for one-legged executions.ConclusionTo strengthen the hips and lower back, BEh seem to be more efficient due to the higher moments, with higher or similar RoMs in the hip and lower back. One-legged BEs seem to provide an effective training for the hamstrings and hip regions without subjecting the spine to excessive loading, possibly promoting this as an effective exercise during training and rehabilitation.
Highlights
Back extension (BE) is a strength exercise for training the dorsal trunk and hip muscles
Different loading conditions act on the spine with different execution forms and lead to different risks of injury because disk deformation and ligament and spinal loading can be reduced if BE exercises are performed with neutral lordosis [11]
The FFT analysis did not show any fatigue between the different trials, which indicated that the breaks were sufficiently long to fully recover between the different execution types
Summary
Back extension (BE) is a strength exercise for training the dorsal trunk and hip muscles. The execution of BEs has been based on the Sorensen test, which was developed to assess the isometric endurance of the dorsal trunk muscles [3, 4]. During this test, subjects lie on a table with their held legs horizontal to the ground and attempt to hold their unsupported upper body stable for as long as possible. In a more recent development of the exercise, instead of a horizontal table, a variable-angle Roman chair is used, which allows the legs to be placed at an angle to the horizontal of, e.g., 45° [1, 5,6,7,8], and thereby allows the highest loading conditions
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