Abdominal wall muscle ultrasound assessment and level of experience in Pilates - an exploratory study

The core refers to a group of muscles that allow optimal force transfer along the body’s kinetic chain and is critical for movement. The goal of this quasi-experimental study was to investigate the relationship between the experience level of Pilates participants and abdominal wall thickness. For this, we compared the thickness of four abdominal muscles—transversus abdominis (TrA), internal oblique (IO), external oblique (EO), and rectus abdominis (RA)—as measured before and after 8 weeks of Pilates training in three conditions, namely, relaxation, abdominal hollowing, and plank exercise. Eighteen participants were distributed into three groups with different levels of Pilates practice—experienced (EG; n=6), inexperienced (IG; n=7), and control (CG; n=5) groups. The RA showed a tendency to increase post-intervention in the EG (all conditions: p=0,002, p=0,006, and p=0,002, respectively for relaxation condition, abdominal hollowing and standing plank). Additionally, significant differences were found in relaxation (p=0.003, d=−0.744) and plank (p=0.009, d=−0.630) conditions in the IG. Significant differences were also registered in the EO muscle in the IG (all conditions: p=0.046, p=0.013, and p=0.008, respectively; d=0.464, d=−0.596, and d=−0.637, respectively). IO muscle thickness tended to increase in the CG in all conditions (p=0.044, p=0.006, and p<0.001, respectively) and the EG in relaxation and plank conditions (p=0.009 and p=0.007, respectively). Within groups, the effects of Pilates practice were more significant post-intervention, with the exceptions being under the contraction condition in the deepest muscles (IO: p=0.109, d=0.083; TrA: p=0.194, d=0.062). Our hypothesis was partially confirmed because 8 weeks of Pilates practice have improved significantly the thickness of the RA and EO muscles in the IG.