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.

Background: Clinical ergonomic advice for sitting posture has been inferred from anthropometry theory and physiology studies. Qualitative observation of posture has been used to argue that postures are too flexed, too extended, too static, too mobile, require insufficient muscle activity or require too much. In other fields of healthcare, evidence is progressed from basic science to clinical trials before an intervention is prescribed, but postural advice has been prescribed from basic science without quantitative studies of postural behaviour. Spinal neuromuscular control can predict development of low back pain, it is affected by spinal pain, and can be trained, but studies examining these variables rarely measure the spinal position of their test subjects. There is a need for more detail of how spinal positions affect regional muscle activity. Study Objectives: The overall aims of this thesis were to quantify sagittal spinal postures in sitting for comparison within and between subjects and tasks, and to detail paraspinal and abdominal muscle activity associated with sitting postures. The studies quantified regional spinal curves in - Study I: typical posture behaviour during a computer task in comparison with standing, - Study II: postures that are achievable in sitting, - Study III: the regional muscle activity associated with sitting postures that have been clinically advocated as ‘ideal’, - Study IV: cohorts with and without a history of low back pain for comparison of regional muscle activity. Results and Conclusions: For clinical trials quantifying postural behaviour, the postural variation within subjects and task conditions in Study I demonstrated the importance of measurement over a prolonged period and subjects performing relevant tasks (as opposed to brief measures such as radiography that have been the standard for posture assessment). The use of surface tracking to quantify regional spinal curves and sagittal balance establish a foundation to investigate the effect of interventions on posture behaviour (eg. chair geometry, posture training, task variables and subject cohorts). Study I also showed that typical sitting posture for a computer task was more flexed at the thoracolumbar spinal region than when subjects deliberately ‘corrected’ their sitting posture, and both sitting postures were flexed at the lumbar region relative to standing. Study II showed that most subjects were unable to sit with spinal curves like those adopted in standing unless facilitation and feedback were provided, although these curves have been clinically advocated as ‘ideal’ posture. If clinical theories about ‘ideal’ sitting posture are correct, then teaching individuals the awareness of spinal position or skill to adopt these postures could be as important for workplace health and safety as other variables such as design and adjustment of office furniture. Study III showed three upright sitting postures that have been clinically advocated as ‘ideal’ were distinguished by incremental changes in activity of the lumbar multifidus muscles. In Study IV, individuals with a history of low back pain showed more incremental activity at the longissimus thoracis muscle to achieve the same sitting postures. If particular postures are shown to be ‘ideal’ in clinical trials, then training for these postures may need to focus on muscular strategies as well as spinal position. The distinct differences in regional muscle activity observed with spinal curves and subject cohorts (Studies III and IV) imply that studies of spinal neuromuscular control should measure or control spinal curves during testing. If spinal posture were controlled, the flat posture (flat surface from ~T5 to sacrum) would have the advantages of being achievable, commonly used in sitting and easily assessed. The flat posture also demonstrated the lowest muscle activity of the upright sitting postures examined, which may improve accuracy of determining muscle activity onset/offset used as an outcome measure for interventions, distinguishing cohorts or as a predictor for low back pain occurrence.

Understanding the predisposing factors for older people falling is imperative as falls can lead to considerable medical and societal costs, loss of independence and reduced quality of life. In particular, it is important to understand more about the many possible intrinsic and extrinsic reasons why older people sometimes fail to maintain their postural stability and fall. Older people are increasingly being encouraged to maintain or increase their daily physical activity levels. Healthy older adults have been shown to have altered postural stability following high intensity physical activity; however it is not known whether postural stability is compromised during everyday levels of physical activity. If it were, it could expose them to greater risk of falling. The overall aim of this series of investigations was to determine whether postural stability was detrimentally affected immediately after moderate intensity physical activity. Five studies were undertaken. Study 1 was carried out to determine the typical duration of activity periods that occur during the daily lives of community-living older people. In this study, the activity period durations of older people living either at home or in an aged care facility were recorded over a continuous 72 hour period using an activity monitoring device. Study 2 determined the effect of an activity protocol, designed to be representative of routine daily activity of community-living older people, on clinical indicators of fatigue. These indicators included maximal voluntary torque from the knee extensor and hip abductor muscles, subjective feelings of fatigue and temporal and spatial gait variables. The physical activity protocol involved a series of tasks carried out continuously for 14 minutes, self-paced at moderate intensity. Tasks included walking, step-ups, mini-lunges and avoiding obstacles. The final three studies compared postural stability before and immediately after the moderate intensity physical activity protocol. Study 3 recorded centre of pressure (COP) displacement during quiet standing with feet together. Study 4 recorded forces and postural electromyographic (EMG) activity during a rapid forward step-up task. Study 5 recorded postural responses to a lateral waist-pull perturbation large enough to elicit a step response. Studies 2, 3 and 4 compared healthy young adults with healthy older and balance-impaired older adults, whilst the final study compared healthy young and old adults. Community-living older people were found to have a wide range of activity period durations and those living in aged care had significantly shorter activity periods compared to those living independently at home. As a result of the findings, an activity period duration of 14 minutes was considered representative of community-living older people’s physical activity exposure. In Study 2, immediately following the physical activity protocol, young, healthy old and balance-impaired older adults all showed no changes in leg strength. All groups felt generally tired and had sensations of local leg muscle fatigue but only the balance-impaired adults were still reporting feelings of fatigue 20 minutes after the activity ceased. This group were also the only group to show altered gait after the activity. Their cadence was reduced compared with before activity and remained reduced 20 minutes later. In quiet standing, all groups demonstrated larger COP displacement in the mediolateral direction following the physical activity. For the step-up task, all groups showed small improvements immediately following the physical activity. These included reductions in the duration of the weight-shift phase, lateral COP displacement during weight-shift and the stance leg hip abductor muscle onset times. Participants also showed a shift in COP position towards the stance side prior to the step following the physical activity. In the final study, the older participants used a cross-over step in response to the lateral perturbation more frequently after the activity than before. This response is a less optimal response compared with a faster and more stable single outward step. When older and younger participants did perform outward steps following the physical activity, they performed them as well as they did before activity. Small changes to some of the measures of postural stability were found during quiet standing, voluntary stepping and to the responses after a lateral perturbation following moderate intensity physical activity. These changes may have been due to the impact of subjective feelings of tiredness experienced by participants. The increased use of a cross-over step strategy to regain balance after a lateral perturbation among healthy older people may mean that older people are at greater risk of falling after physical activity. However, the findings from this series of studies do not convincingly support a clinically significant detrimental effect on older people’s postural stability immediately following routine daily physical activity. This thesis has begun to investigate the effect of physical activity at daily levels on older people’s postural stability, however further investigations are recommended.

A range of signal processing techniques have been adopted and developed as a methodology which can be used in developing an intelligent surface electromyography (SEMG) signal classifier. An intelligent SEMG signal classifier would be used for recognising and treatment of musculoskeletal pain and some neurological disorders by physiotherapists and occupational therapists. SEMG signals displays the electrical activity from a skeletal muscle which is detected by placing surface electrodes placed on the skin over the muscle. The key factors of this research were the investigation into digital signal processing using various analysis schemes and the use of the Artificial Neural Network (ANN) for signal classification of normal muscle activity. The analysis schemes explored for the feature extraction of the signals were the Fast Fourier Transform (FFT), Short Time Fourier Transform (STFT), Continuous Wavelet Transform (CWT), Discrete Wavelet Transform (DWT) and Discrete Wavelet Packet Transform (DWPT).Traditional analysis methods such as FFT could not be used alone, because muscle diagnosis requires time-based information. CWT, which was selected as the most suitable for this research, includes time-based information as well as scales, and can be converted into frequencies, making muscle diagnosis easier. CWT produces a scalogram plot along with its corresponding frequency-time based spectrum plot. Using both of these plots, overviewed extracted features of the dominant frequencies and the related scales can be selected for inputs to train and validate an ANN. The purpose of this research is to classify (SEMG) signals for normal muscle activity using different extracted features in an ANN. The extracted features of the SEMG signals used in this research using CWT were the mean and median frequencies of the average power spectrum and the RMS values at scales 8, 16, 32, 64 and 128. SEMG signals were obtained for a 10 second period, sampled at 2048 Hz and digitally filtered using a Butterworth band pass filter (5 to 500 Hz, 4th order). They were collected from normal vastus lateralis and vastus medialis muscles of both legs from 45 male subjects at 25%, 50%, and 75% of their Maximum Voluntary Isometric Contraction (MVIC) force of the quadriceps. The ANN is a computer program which acts like brain neurons, recognises, learns data and produces a model of that data. The model of that data becomes the target output of an ANN. Using the first 35 male subjects' data sets of extracted features, the ANN was trained and then validated with the last 10 male subjects' data sets of the untrained extracted features. The results showed how accurate the untrained data were classified as normal muscle activity. This methodology of using CWT for extracting features for analysing and classifying by an ANN for SEMG signals has shown to be sound and successful for the basis implementation in developing an intelligent SEMG signal classifier.

Doctor of Philosophy / In this thesis, three experiments were conducted to monitor: (i) muscle oxygenation and electromyographic activity of the biceps brachii after exercise-induced muscle damage (ii) muscle oxygenation after downhill walking-induced muscle damage, and, (iii) muscle oxygenation following a bout of vigorous concentric exercise. Maximal eccentric exercise (EE) of biceps brachii resulted in significantly increased mean resting oxygen saturation and decreased deoxyhaemoglobin. During isometric contractions at 50% and 80% of subjects’ maximum voluntary torque (MVT), oxygen desaturation and resaturation kinetics and volume were significantly decreased after EE, and these declines were significantly prevalent over the following 6 days. Additionally, a significant shift in median frequency intercept (measured by electromyography; EMG) towards lower frequencies was observed during isometric contractions at both 50% and 80% MVT after EE in the exercised arm. After an exhaustive session of downhill walking, another form of EE, resting total haemoglobin and oxyhaemoglobin decreased. Furthermore, during isometric contractions at 30%, 50% and 80% of MVT, prolonged and significant increases were observed in oxygen desaturation and resaturation kinetics and volumes after ambulatory EE. In contrast to the two EE experiments, concentric contractions did not evoke any prolonged changes in muscle oxygenation. Collectively, the findings of this thesis revealed significant and prolonged changes in muscle oxygenation at rest and during exercise, following sessions of strenuous eccentric exercise. Although not clear, the possible mechanism responsible for the changes in muscle oxygenation after EE could be increased resting muscle oxygen utilization due to probable muscle damage and a subsequent requirement of energy demanding repair processes. Concentric exercise resulted in fatigue, but it did not affect muscle oxygenation. Although a prolonged reduction in EMG median frequency intercept was observed after EE, this was not closely time-associated with the biochemical, anthropometric or functional markers of muscle damage.

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser. - På omsl. felaktigt: Karolinska University Press.

Diss. (sammanfattning) Linköping : Univ., 2005. / Härtill 5 uppsatser.

Thesis--Copenhagen. / Summary in Danish. Includes bibliographical references (p. 127-130).