Forced expiration: a simple technique that acutely increases core muscle contraction in mild chronic non-specific low back pain

The abdominal drawing-in maneuver (ADIM) is widely used to activate the transverse abdominis muscle (TrA). However, the ADIM technique might be challenging to understand and perform correctly, causing the compensation of the internal and external oblique muscles (IO and EO, respectively). The forced expiration (FE) technique has been proposed to activate TrA with minimal contraction of IO and EO. This study aimed to compare the muscle contraction of TrA, IO, and EO in individuals with chronic non-specific low back pain (CNLBP) between ADIM and FE techniques. This study used a crossover design. 15 individuals with mild CNLBP were recruited. Participants were asked to perform ADIM and FE in a random order. Ultrasound imaging was used to collect TrA, IO, and EO thickness at rest and during those techniques. These data were further used to calculate the percent change in muscle thickness from resting (%Change). A 2-way repeated measure ANOVA with post-hoc least significant difference (LSD) was performed to determine the effects of different techniques on lateral abdominal muscles. Results showed a significant technique*muscle interaction (P = 0.001), while post-hoc LSD demonstrated significant differences (P < 0.001) in %Change between TrA and IO, as well as TrA and EO for both techniques. However, the results showed that FE elicited a significantly greater TrA contraction than ADIM (P = 0.002). Findings indicate that both techniques can isolate the TrA from IO and EO, but the FE technique showed a greater %Change in TrA compared to the ADIM. These findings suggest that FE is a more potent maneuver for maximizing TrA contraction and may serve as a valuable alternative approach in core stabilization programs for individuals with mild CNLBP.