Comparison of two different feedback techniques for activating the transversus abdominis: An observational study

BACKGROUND: The transversus abdominis (TrA) is an important muscle for spinal stabilization. The abdominal draw-in maneuver (ADIM) is a method that selectively activates the TrA without overactivation of the external oblique (EO) and internal oblique (IO). Individuals with low back pain may have trouble in understanding proper contraction of the TrA. OBJECTIVE: The aim of this study was to investigate the differences between two feedback techniques to re-educate the TrA. METHODS: One hundred eighty healthy volunteers (123 female, 57 male) were randomized into two groups. The ADIM was performed with different feedback methods: conventional (verbal and tactile) feedback and visual feedback from real-time ultrasound images. RESULTS: A within-group comparison revealed a significant increase in the thickness of the TrA, IO, and EO during the ADIM (p< 0.001) in both groups. The mean change (SD) in the thickness of the TrA and IO between rest and the ADIM was an increase of 2.541.25 and 1.882.14 in group 1 and 1.821.27 and 1.241.87 in group 2, respectively (p< 0.001). No significant differences were observed in EO thickness between the two groups. CONCLUSIONS: Although visual biofeedback shows a greater effect on ADIM training, both approaches are applicable, and clinicians may decide on which to use based on their clinical environment and experience.

Pick’s theorems for dissipative operators

Let H be a complex Hilbert space and let A be a bounded linear transformation on H. For a complex-valued function f, which is analytic in a domain D of the complex plane containing the spectrum of A, let f (A) denote the operator on H defined by means of the Riesz-Dunford integral. In the present paper, several (presumably new) versions of Pick?s theorems are proved for f (A), where A is a dissipative operator (or a proper contraction) and f is a suitable analytic function in the domain D.

Proper contractions and invariant subspaces

LetTbe a contraction andAthe strong limit of{T∗nTn}n≥1. We prove the following theorem: if a hyponormal contractionTdoes not have a nontrivial invariant subspace, thenTis either a proper contraction of class𝒞00or a nonstrict proper contraction of class𝒞10for whichAis a completely nonprojective nonstrict proper contraction. Moreover, its self-commutator[T*,T]is a strict contraction.