Immediate Effect of Four Exercises on Linea Alba Thickness, Distortion and Inter-Recti Distance in Parous Women.

BACKGROUND AND PURPOSE: This cross-sectional study assessed the impact of four abdominal exercises (crunch, abdominal drawing-in maneuver [ADIM], pelvic floor muscle contraction, and de Gasquet basic exercise) on inter-recti distance (IRD) and linea alba (LA) distortion and thickness in parous women.

METHODS

Parous women underwent ultrasound assessment during four abdominal exercises. The primary outcome was IRD at supra- and infraumbilical levels. Secondary outcomes were LA distortion and thickness. Transversus abdominis (TrA) activation was assessed simultaneously. Exercises were compared using linear mixed-effects models and Tukey-adjusted pairwise tests.

RESULTS

Fifty-four parous women participated. Supraumbilically, the crunch showed the greatest IRD decrease (EMM + 2.48 mm), but this was not significantly different from ADIM, pelvic floor muscle contraction, or de Gasquet exercise (Tukey p ≥ 0.07). The crunch was associated with increased LA distortion during the exercise compared with other exercises (supra: + 0.26 ± 0.05; infra: + 0.35 ± 0.07 distortion units; both p < 0.001), while the other three exercises reduced or maintained distortion during the exercise. Supraumbilical LA thickness increased during crunch compared with the other exercises (Tukey p ≤ 0.05). TrA effects were exercise-specific: greater TrA thickening was associated with greater IRD decrease during ADIM, whereas lower TrA thickening was associated with greater IRD decrease during crunch.

DISCUSSION: The crunch showed the largest supraumbilical immediate reduction in IRD but was accompanied by increased LA distortion. In contrast, the other three exercises were associated with smaller IRD changes and lower distortion. Lower TrA activation during crunch was associated with increased LA deformation, and apparent medial convergence of the rectus abdominis during the exercise.

TRIAL REGISTRATION: This research was registered on ClinicalTrials (NCT04501302).