Co-contractive activation of the superficial multifidus during volitional preemptive abdominal contraction.

Objective: To investigate whether the superficial multifidus (MF) muscle at the lower lumbar spine displayed co-contraction during volitional preemptive abdominal contraction (VPAC) through the abdominal drawing-in maneuver (ADIM) or the abdominal bracing maneuver (ABM) in 3 different postural positions.

Design: A within-subject cohort design.

Setting: A clinical laboratory.

Participants: A healthy convenience sample of 21 women and 13 men; mean age (SD), 25.5 ± 6.5 years.

Methods: We collected surface electromyographic measurements for the superficial MF at the L5 vertebral level and abdominal wall muscles. Ultrasound imaging was used during screening and testing sessions for confirming transverse abdominis muscle activation while subjects maintained a relaxed state without volitional abdominal contraction (no-VPAC) and performed ADIM and ABM in 3 postural positions: supine, 4-point kneeling, and upright standing.

Main Outcome Measurement: The frequency of superficial MF co-contraction occurrences (percentage of the total number of conditions) was measured during ADIM and ABM in 3 different postural positions.

Data Analyses: A Cochran Q test for k-related samples (α = 0.05) was used for data analysis.

Results: Activation of the abdominal wall by using either VPAC strategy resulted in a significantly greater MF co-contraction occurrence when compared with no-VPAC in each position. The ABM produced a significantly higher MF co-contractive occurrence versus the ADIM in the supine position.

Conclusion: Both VPAC strategies produced a co-contractive MF response, which appears to be important for lumbar segmental stabilization and control. Analysis of the results suggests that VPAC strategies are appropriate for coactivating the MF, which can enhance spinal protection and rehabilitation responses.