Effect of the abdominal draw-in manoeuvre in combination with ankle dorsiflexion in strengthening the transverse abdominal muscle in healthy young adults: a preliminary, randomised, controlled study.

Objectives: To compare the effect of the abdominal draw-in manoeuvre with the abdominal draw-in manoeuvre in combination with ankle dorsiflexion on changes in muscle thickness and associated muscle activity in abdominal muscles.

Design: A preliminary, randomised, controlled study.

Setting: University laboratory.

Participants: Forty healthy adults (18 males, 22 females) were allocated at random to the experimental group [mean age (SD) 24 (1.6) years, n=20] or the control group [mean age (SD) 24 (1.9) years, n=20]. The experimental group performed the abdominal draw-in manoeuvre in combination with ankle dorsiflexion, and the control group performed the abdominal draw-in manoeuvre alone, five times a day.

Main Outcome Measures: Ultrasonography and electromyography were used to determine the intervention-related changes in muscle activity and the thickness of abdominal muscles during the abdominal draw-in manoeuvre or the abdominal draw-in manoeuvre in combination with ankle dorsiflexion.

Results: A significant difference was found in the thickness of the transverse abdominal muscle between the groups [mean difference 0.24 cm, 95% confidence interval (CI) 0.08 to 0.40, P=0.005. On electromyography, a significant difference was demonstrated in the amplitude of the transverse abdominal muscle contraction between the two techniques in the experimental group (mean difference 68.76 mV, 95% CI 53.16 to 84.36, P=0.000. The intra-class correlation coefficient (ICC(2,1)) showed excellent test-retest reliability of ultrasound measurement of the abdominal muscles: 0.96 (95% CI 0.85 to 0.99) for the transverse abdominal muscle, 0.87 (95% CI 0.62 to 0.98) for the internal oblique muscle and 0.77 (95% CI 0.44 to 0.96) for the external oblique muscle.

Conclusions: This is the first study to demonstrate the additive effect of ankle dorsiflexion on deep core muscle thickness and activity, thus contributing to existing knowledge about therapeutic exercise for the effective management of low back pain.