Affiliations: School of Kinesiology and Health Science, Faculty of Health, York University, Toronto, ON, Canada
Correspondence:
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Corresponding author: Janessa D.M. Drake, 2030 Sherman Health Science Research Centre, School of Kinesiology and Health Science, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada. Tel.: +1 416 736 2100, x. 33568; Fax: +1 416 736 5772; E-mail:jdrake@yorku.ca
Abstract: BACKGROUND: The flexion-relaxation phenomenon (FRP) in standing is
a specific and sensitive diagnostic tool for low back pain. Seated flexion
as an alternative could be beneficial for certain populations, yet the
behavior of the trunk extensors during seated maximum flexion compared to
standing flexion remains unclear. OBJECTIVE: Compare FRP occurrences and spine angles between seated
and standing flexion postures in three levels of the erector spinae muscles. METHODS: Thirty-one participants free of back pain performed seated
and standing maximum trunk flexion. Electromyographical signals were
recorded from the bilateral lumbar (L3), lower-thoracic (T9), and
upper-thoracic (T4) erector spinae and assessed for the occurrence of
FRP. Spine angles corresponding to FRP onset and cessation were determined,
and FRP occurrences and angles were compared between posture and muscle. RESULTS: FRP occurrence was similar in standing and seated maximum
flexion across all muscles, with the lumbar muscles showing the greatest
consistency. Standing FRP onset and cessation angles were consistently
greater than the corresponding seated FRP angles. CONCLUSION: Considering the similar number of FRP occurrences,
seated maximum flexion may constitute an objective criterion for low back
pain diagnosis. Future work should seek to confirm the utility of this test
in individuals with low back pain.
