Trunk muscle activation patterns, lumbar compressive forces, and spine stability when using the Bodyblade

Spine stability is known to be dependant on the coordinated activity of many trunk muscles. Muscles that are anterior, posterior, or lateral to the spine must co-contract with varying amounts [...]
Background and Purpose The objective of this study was to analyze the trunk muscle activation patterns, spine kinematics, and lumbar compressive forces that occur when using the Bodyblade, a popular tool in physical medicine clinics. Subjects The participants were 14 male subjects who were healthy and who were recruited from a university population. Methods With data collected from surface electromyography of selected trunk and shoulder muscles, video analysis, and a 3-dimensional lumbar spine position sensor, modeling methods were used to quantify L4-5 compressive forces and spine stability. Results Large-amplitude oscillation of a vertically oriented Bodyblade resulted in the greatest activation levels of the internal oblique and external oblique muscles (average amplitude = 48% and 26% of maximal voluntary isometric contraction, respectively), which were associated with L4-5 compressive forces as high as 4,328 N. Instantaneous stability increased with well-coordinated effort, muscle activation, and compression, but decreased when subjects had poor technique. Discussion and Conclusion The way the Bodyblade is used may either enhance or compromise spine stability. Associated lumbar compressive forces may be inappropriate for some people with compression-intolerant lumbar spine pathology.