Voluntary and automatic recruitment of superficial and deep abdominal muscles in adults with and without cystic fibrosis

Recruitment patterns of the superficial and deep abdominal muscles have been well documented in the general population, but not in a group of individuals with a chronic cough, such as individuals with cystic fibrosis (CF), which may alter the recruitment patterns between the abdominal muscles. Therefore the two objectives of this study were (1) to identify whether recruitment of the superficial and deep abdominal muscles during abdominal hollowing (AH) and unilateral leg load (ULL) tasks differed between individuals with CF and a non-CF control group (C); and (2) to compare the muscle activity between the superficial and deep abdominal muscles across these tasks. Methods: Twenty-eight participants (14 with CF and 14 controls) performed (i) AH in supine at three target pressures of a pressure biofeedback unit (PBU) and (ii) a right-sided ULL. Surface electromyography (EMG) of the abdominal muscles was recorded and the amplitude of the signal was normalized to a maximum value (% max). Results: A 3-way repeated measures ANOVA showed a muscle × task interaction during the AH, but no between group differences. Bonferonni post hoc tests on pooled data showed the deep abdominal muscles to be significantly more active than the superficial muscles. A 2-way repeated measure ANOVA indicated no group differences during the ULL. Discussion: The results of this study demonstrate that adults with stable CF do not recruit their abdominal muscles differently from healthy control subjects during the AH and the ULL tasks. This suggests that coughing is not a risk factor for developing abdominal muscles imbalances in adults with cystic fibrosis.