Transversus Abdominis and Obliquus Internus Activity During Pilates Exercises: Measurement With Ultrasound Scanning

Objective: To assess activity of transversus abdominis (TrA) and obliquus internus abdommis (OI) muscles during classical Pilates exercises performed correctly and incorrectly, and with or without equipment. Design: Repeated-measures descriptive study. Setting: Pilates studio. Participants: A volunteer sample of women (n=18) and men (n=8), mean age +/- SD (43 +/- 14y), with more than 6 months classical Pilates training and no back pain or other condition likely to influence abdominal muscle activity. Interventions: Participants performed Pilates imprint, hundreds A and B, roll-up, and leg-circle exercises on a mat. The hundreds exercise was also performed on a reformer (sliding platform). Mat imprint and hundreds exercises were instructed to be performed correctly (with abdominal drawing-in) or incorrectly (without drawing-in). Main Outcome Measure: Thickness of TrA and OI middle fibers measured with ultrasound imaging. Results: TrA thickness increased during the mat imprint, hundreds A, hundreds B, leg-circle, and roll-up exercises (all P=.001) compared with resting. OI thickness increased during the mat imprint, hundreds A, hundreds B, leg-circle (all P=.001), and roll-up exercises (P=.002) compared with resting. TrA thickness during reformer hundreds B was greater than during mat hundreds B (P=.011); OI thicknesses were not different for this comparison. During incorrect imprint, neither TrA or OI thicknesses were different to resting. TrA and OI muscle thicknesses were moderately correlated (R=.410; P=.001). Conclusions: This study provides the first evidence that a selection of classic Pilates exercises activates TrA and OI. Use of the reformer exercise machine can result in greater TrA activation in some exercises. TrA and OI did not function independently during these exercises. Research into the training effects of Pilates or in patient populations can be undertaken using ultrasonography in submaximal exercises.