The Effect of Distractive Function on Volitional Preemptive Abdominal Contraction During a Loaded Forward Reach in Normal Subjects

Abstract Background Volitional preemptive abdominal contraction (VPAC) is used to protect the spine and prevent injury. No published studies to data have examined the effect of distraction on VPAC use during function. Objective To examine the effect of an auditory distraction (“Stroop task”) on healthy subjects' ability to sustain VPAC by use of the abdominal drawing-in maneuver during loaded forward reach. Design Within-subjects, repeated-measure cohort design. Setting Clinical laboratory setting. Participants Convenience sample of 42 healthy individuals (ages 20-57 years). Methods Transversus abdominis (TrA) thickness was measured with M-mode ultrasound imaging. Each subject performed Stroop versus no Stroop during 4 conditions: (1) without VPAC, quiet standing; (2) with VPAC, quiet standing; (3) without VPAC, forward reach; and (4) with VPAC, forward reach. An investigator blinded to the conditions measured the first 10 subjects to establish intratester reliability of probe/transducer placement and TrA measurement. Data Reduction TrA thickness (mm) change represented VPAC performance. A single investigator measured onscreen TrA thickness twice at each second from second-6 through -10 on a recorded ultrasound imaging sequence. Results A 2 (Stroop) × 4 (Activity) repeated-measures analysis of variance found no significant Stroop × Activity interaction [F(3, 93) = 0.345, P = .793] and no main effect for Stroop [F (1,31) = 1.324, P = .259] but found a significant main effect for activity [F (3,93) = 17.729, P < .001]. Tukey post-hoc pairwise comparisons demonstrated significant differences between VPAC versus no-VPAC conditions, except between quiet standing/yes-VPAC and loaded forward reach/no-VPAC conditions ( P = .051). The interclass correlation coefficient (3,2) for probe/transducer placement reliability was 0.87, 0.91, 0.92, and 0.93 for conditions 1-4, respectively. The interclass correlation coefficient (3,2) for TrA measurement reliability was 0.96, 0.99, 0.99, and 0.99 for conditions 1-4, respectively. Conclusion A distracting executive function (Stroop task) did not produce a significant negative impact on normal individuals' ability to sustain a VPAC during quiet standing or loaded forward reach activities.