Introduction: The primary purpose of this research was to determine whether women with stress urinary incontinence (SUI) demonstrate pelvic floor muscle (PFM) strength or endurance deficits and/or changes in the motor control patterns used during maximum voluntary PFM contractions (PFM MVCs) and coughing. A secondary purpose was to determine the effect of age on these parameters. Methods: After first validating the use of vaginal pressure to study the functional output of the PFMs, three studies were carried out to address these objectives. In two studies vaginal pressure and PFM and abdominal muscle electromyography (EMG) data were recorded simultaneously during PFM MVCs and maximum effort coughs in continent women, women with mild SUI and women with moderate to severe SUI in both supine and standing. In the final study, the effect of continence status and age on PFM strength and endurance was measured with vaginal pressure. Results: Changes in vaginal pressure induced by PFM MVCs and coughing were found to reflect changes in urethral pressure. The women with SUI and the continent women were found to be equally able to produce peak PFM EMG and vaginal pressure amplitudes during PFM MVCs and coughs. Compared to the continent women, the women with SUI delayed activating their abdominal muscles during the PFM MVCs. During coughing, vaginal pressure and PFM EMG peaked simultaneously in the continent women, while in the women with SUI vaginal pressure peaked after PFM EMG. During both the PFM MVCs and the coughs, the EMG activity in all of the muscles tested was higher at the onset of vaginal pressure generation in the women with SUI compared to the continent women. No difference was found in PFM endurance between the women with and without SUI. The ability to generate peak vaginal pressure during coughing decreased with age. Conclusions: PFM weakness does not appear to play a significant role in SUI. Rather, the results of this research suggest that a combination of motor control deficits and delays in pressure transmission are associated with SUI in women. / Thesis (Ph.D, Rehabilitation Science) -- Queen's University, 2009-09-21 09:37:12.923

The pelvic floor muscles (PFM) form the base of the abdominal canister, and like the other muscle groups around the canister, the abdominal muscles and the diaphragm, they contribute to and are affected by pressures within the canister. But they also have a role in organ support and continence. In urinary incontinence, clinical rehabilitation has targeted the PFM in isolation. It aims to build up strength and endurance of these muscles, but without consideration of the influence of intra-abdominal pressure, and therefore the co-ordination of muscles that generate that pressure, on PFM activity. Strengthening of the PFM has not resolved incontinence for all women, and the benefits are not sustained in the long term. Thus consideration of factors beyond the pelvic floor (PF) may lead to better outcomes for rehabilitation in both the short and long term. Thus these studies aimed to investigate the influences of abdominal muscle activity and spinal posture on the recruitment of the PFM. The studies firstly investigated the association between the abdominal and PFM during voluntary tasks. Further studies examined the effect of automatic recruitment of the PFM and the abdominal muscles with postural disturbances and changes in spinal posture, and whether there was a difference in recruitment between layers of the PFM complex during function. Electromyographic (EMG) studies, using fine wire and/or surface electrodes, were performed to record patterns of muscle activity, while, in selected studies, this was accompanied by pressures recorded within the stomach, urethra, bladder, vagina, anus and rectum, to monitor the effects of the striated muscle activity on intra-abdominal pressure and urethral function. When the PFM were voluntarily contracted in healthy women, there was a co-ordinated response in all the abdominal muscles, which varied with the position of the lumbar spine. Conversely, when the lower abdominal muscles were drawn in towards the spine there was an increase in IAP, urethral pressure and PFM EMG activity. Relaxation of the abdominal muscles and bulging of the relaxed abdominal wall decreased PFM activity and urethral pressure below their resting baselines. Thus, voluntary activation of the abdominal or PFM influences activity in the other muscle group. Other studies investigated the automatic responses of abdominal and PFM during breathing, postural perturbation, sitting and coughing. Quiet breathing was associated with modulation of PFM EMG with greater activity during expiration than inspiration, in association with variations in abdominal muscle activity. Hypercapnoea accentuated these results. Postural perturbations generated co-activation of the PF and abdominal muscles before the onset of deltoid activity with sustained activity through out repeated arm movements. Changes in spinal posture also affected PFM activity. Like the abdominal muscles, PFM were less active when sitting in a slumped position. Similar changes occurred in women with stress urinary incontinence but with lower pelvic floor muscle activity levels. Women with stress urinary incontinence also had less lordosis of the lumbar spine in upright sitting and a trend for greater superficial abdominal muscle activity than continent women. Activity of the superficial, but not deep, PFM during coughing, was affected by different sitting postures, with greater activity during coughing in slumped than in upright postures. Different breathing patterns and changes in posture also affected IAP and abdominal muscle recruitment patterns during coughing. Investigation of PFM activity during functional tasks indicates that factors beyond the PF influence its activity. The findings from these studies indicate that PFM activity is inter-related with spinal posture and abdominal muscle activity. While most of these studies were conducted in healthy women, there are a number of different types of PF problems in women, in which the mechanics of the dysfunction differ from stress urinary incontinence. PFM activity has not been investigated in all types of PF dysfunction. The findings of co-ordinated recruitment of the abdominal and PFM and the effect of spinal posture on PFM function provide some evidence that PFM rehabilitation should not be undertaken in isolation, and that there is a likely advantage from exercising with a neutral lumbar spine. There is a need for further investigation of this co-ordinated muscle recruitment in subjects with different types of dysfunction, not just stress urinary incontinence. Findings from such investigations could then point the way forward to improved rehabilitation methods for people with problems, and more suitable methods of maintaining pelvic floor health.