Date of Award
Doctor of Philosophy (PhD)
Clinical and Translational Rehabilitation Health Sciences
Hunter, Sandra K.
Neumann, Donald A.
Efficient abdominal muscle function is important for functional mobility in men and women, and dysfunction of these muscles has been associated with impaired function such as low back pain. This dissertation explored abdominal muscle function in healthy young men and young women who have never been pregnant (nulligravid). As pregnancy and child birth also impact the tissues of the abdominal wall, this dissertation will also explore abdominal muscle function in postpartum women. This dissertation involved three primary aims. Aim1 compared abdominal muscle function and experimental pain perception in males and nulligravid females. Maximal strength over a range of trunk angles, force steadiness and fatigability of the trunk flexor muscles were assessed. Although the trunk flexor muscles of males were stronger than females, there were minimal differences in fatigability during an intermittent submaximal contraction. Aim 2 determined the impact of pregnancy and childbirth on trunk flexor strength and fatigability at 8-10 weeks and 24-26 weeks postpartum. To determine the impact of delivery method, trunk flexor function was also compared in women who underwent Cesarean or vaginal delivery. Postpartum women were significantly weaker and more fatigable than control women up to 26 weeks postpartum. At 8-10 weeks postpartum, women who experienced Cesarean delivery were more fatigable than women who delivered vaginally, with no difference between delivery types at 26 weeks postpartum. Finally, Aim 3 assessed a novel test of abdominal function that may be used in the clinic, and compared fatigability of the lumbopelvic stabilizing muscles and experimental pain in postpartum and nulligravid women, and across delivery types. The lumbopelvic stabilizing muscles of postpartum women were more fatigable than control women up to 26 weeks postpartum in the clinically adapted test. Postpartum women were also more sensitive to pain at the abdomen than control women at 8 weeks and 26 weeks after childbirth. Thus, women had impaired abdominal function and increased pain at least 6 months after childbirth, with greater initial decrements in function after Cesarean delivery compared with vaginal delivery. These findings highlight the importance of assessment and rehabilitation of the abdominal muscles after pregnancy.