Estimates of persistent inward current in human motor neurons during postural sway

Persistent inward current (PIC) is a membrane property critical for increasing gain of motor neuron output. In humans, most estimates of PIC are made from plantarflexor or dorsiflexor motor units with the participant in a seated position with the knee flexed. This seated and static posture neglects the task-dependent nature of the monoaminergic drive that modulates PIC activation. Seated estimates may drastically underestimate the amount of PIC that occurs in human motor neurons during functional movement. The current study estimated PIC using the conventional paired motor unit technique which uses the difference between reference unit firing frequency at test unit recruitment and reference unit firing frequency at test unit de-recruitment (∆F) during triangular-shaped, isometric ramps in plantarflexion force as an estimate of PIC. Estimates of PIC were also made during standing anterior postural sway, a postural task that elicits a ramped increase and decrease in soleus motor unit activation similar to the conventional seated ramp contractions. For each motor unit pair, ∆F estimates of PIC made during conventional isometric ramps in the seated posture were compared to those made during standing postural sway. Baseline reciprocal inhibition (RI) was also measured in each posture using the post-stimulus time histogram (PSTH) technique. Hyperpolarizing input has been shown to have a reciprocal relationship with PIC in seated posture and RI was measured to examine if the same reciprocal relationship holds true during functional PIC estimation. It was hypothesized that an increase in ∆F would be seen during standing compared to sitting due to greater neuromodulatory input. We found that ∆F estimates during standing postural sway were equal (2.44 ± 1.17, p=0.44) to those in seated PIC estimates (2.73± 1.20) using the same motor unit pair. Reciprocal inhibition was significantly lower when measured in a standing posture (0.0031 ± 0.0251,

Cervical flexion relaxation phenomenon and the modulating effect of trunk flexion angle

The purpose of this study was to assess the presence of the flexion relaxation phenomenon (FRP) in cervical paraspinal musculature in an upright standing posture, and to examine the modulating effect of non-neutral trunk postures on cervical FRP (cFRP). Cervical spinal angles and muscle activation patterns were monitored in 17 participants while performing a neck flexion task in six postures. EMG and angle traces from the flexion trials were used to determine the presence and magnitude of the cFRP (Extension Relaxation Ratio: ERR) and the cervical angles associated with cFRP (onset and cessation angles). The cFRP was observed in the cervical paraspinal muscles (CPS) muscles unilaterally in 11 participants (64.7 %), and bilaterally in 8 participants (47.1 %), across all postures and conditions. Onset angle was lower and ERR was higher in the 45░ trunk inclination condition compared to the upright and slumped conditions. ERRs and onset angles were not significantly different in the slumped condition compared to the upright condition. The data from this study contributed to the knowledge base for the under-researched area of cFRP

Effects of posture regulation on mood states, heart rate and test performance in children

This experiment aimed to investigate the effects of seated posture regulation on children’s psychological and physiological state and test performance. Thirty-eight boys (mean age: 12.3 ± 0.53 years) participated in both upright and normal posture conditions in a within-participants design. Participants completed a two-dimensional mood scale to measure psychological mood states and performed three tests (calculation, listening comprehension and word memory). Heart rate, as an index of physiological arousal state, was measured. Upright posture resulted in greater vitality and pleasure, as well as increased heart rate, compared with normal posture. Upright posture also led to significantly higher scores for calculation and listening comprehension tests. Moreover, increases in vitality level positively influenced increases in calculation and listening comprehension test scores. This study suggests that adopting an upright posture results in maintaining a positive psychological state and improving test performance of children

Learning Redundant Motor Tasks With and Without Overlapping Dimensions: Facilitation and Interference Effects

Prior learning of a motor skill creates motor memories that can facilitate or interfere with learning of new, but related, motor skills. One hypothesis of motor learning posits that for a sensorimotor task with redundant degrees of freedom, the nervous system learns the geometric structure of the task and improves performance by selectively operating within that task space. We tested this hypothesis by examining if transfer of learning between two tasks depends on shared dimensionality between their respective task spaces. Human participants wore a data glove and learned to manipulate a computer cursor by moving their fingers. Separate groups of participants learned two tasks: a prior task that was unique to each group and a criterion task that was common to all groups. We manipulated the mapping between finger motions and cursor positions in the prior task to define task spaces that either shared or did not share the task space dimensions (x-y axes) of the criterion task. We found that if the prior task shared task dimensions with the criterion task, there was an initial facilitation in criterion task performance. However, if the prior task did not share task dimensions with the criterion task, there was prolonged interference in learning the criterion task due to participants finding inefficient task solutions. These results show that the nervous system learns the task space through practice, and that the degree of shared task space dimensionality influences the extent to which prior experience transfers to subsequent learning of related motor skills

Investigating Occupational Factors Linked to Back Pain: Repetitive Lifting Strategies and a Method for Examining Effects of Vibration

Low back pain results in a significant burden to industrial nations worldwide from the medical costs and the loss of work productivity. The objective of the current work was to investigate repetitive lifting with high torso flexions and vibration, all factors linked to low back pain. In the first study, lumbar-pelvic coordination was examined in novice and experienced lifters. It was hypothesized that novice lifters would select a lumbar-pelvic coordination that reached the kyphotic limits of their lumbar range of motion (ROM) while experienced lifters would select a more neutral strategy. Twenty-seven subjects participated in a repetitive lifting experiment to examine the kinematics and energetics of different lifting strategies. Three lifting strategies were examined using individual lumbar ROM for normalization. The first was a self-selected strategy followed by two strategies trained with a biofeedback. The trained strategies included a strategy approaching the kyphotic limits of ROM and a neutral strategy maintaining near the middle of ROM. The results demonstrate novice lifters select a lumbar-pelvic coordination approaching the kyphotic limits of their range of motion while experienced lifters remain near the middle. The energetics of the lifting task were also examined, but found no significant differences between the trained lifting strategies. In another study, seven subjects participated in a study attempting to design a proprioceptive measurement acceptable for the occupational setting. The design criteria the task need to meet included: 1) portable, 2) minimal set up, 3) easy for subjects to understand, 4) minimal data collection time, and 5) able to identify effects of vibration exposure. A seated sway target pursuit task was designed to examine four tasks of increasing complexity to identify the most appropriate task for the occupational setting. The target pursuit tasks included stable sway, linear tracking in ML and AP directions, and tracking a circle. Limited detected effects of vibration in these tasks suggest that further development is required. In both efforts, dynamic control of lumbar motion was examined using repetitive trunk motion tasks. In the lifting study, experienced lifters chose a more neutral lumbar-pelvic coordination strategy, suggesting training such a strategy could reduce injury incidence

Grasp modelling with a biomechanical model of the hand

The use of a biomechanical model for human grasp modelling is presented. A previously validated biomechanical model of the hand has been used. The equilibrium of the grasped object was added to the model through the consideration of a soft contact model. A grasping posture generation algorithm was also incorporated into the model. All the geometry was represented using a spherical extension of polytopes (s-topes) for efficient collision detection. The model was used to simulate an experiment in which a subject was asked to grasp two cylinders of different diameters and weights. Different objective functions were checked to solve the indeterminate problem. The normal finger forces estimated by the model were compared to those experimentally measured. The popular objective function sum of the squared muscle stresses was shown not suitable for the grasping simulation, requiring at least being complemented by task-dependent grasp quality measures

Accuracy of pelvis repositioning in individuals with and without low back pain

Proprioception allows the body to maintain proper orientation during static and dynamic activities. In the upper and lower extremities, research has demonstrated a loss of some aspects of proprioception and improvement in proprioception with retraining. It was hypothesized that persons with low back pain lose some elements of proprioception, although research in this area is relatively new. One aspect of proprioception, repositioning accuracy, was examined in this study. The primary purpose of this study was to compare repositioning accuracy of individuals with CLBP and healthy controls. Specifically, the ability to reposition the pelvis into a neutral position was examined in standing and seated positions. A secondary purpose of the study was to examine the inter-relationships between low back pain, repositioning accuracy and physical measurements. The ability to repositioning the pelvis into neutral in both standing and seated positions was tested in 19 volunteers aged 35-55 years old from the University of Tennessee at Knoxville and surrounding community. The participants were divided into two groups based on their Oswestry Low Back Pain Disability Questionnaire score (ODQ). Individuals with an ODQ score of zero were placed in the control group (n = 10). The chronic low back pain group (CLBP; n = 9) included individuals with an ODQ score greater than zero. The groups were similar with regards to age, height, weight, and body mass index. An electronic goniometer (elgon) was used to measure total lumbar range of motion (TROM), baseline neutral position, and neutral repositioning in both standing and seated positions. Each participant underwent a neutral spine training session following anthropometric, flexibility and strength measurements. Standing TROM was calculated as the sum of extreme anterior tilt and extreme posterior tilt. Following TROM testing, baseline standing neutral spine position was recorded for each individual. The participants then attempted to replicate their standing neutral position. Repositioning error was calculated as the absolute difference between the baseline neutral position and the repositioned neutral position. The same protocol was repeated in an unsupported seated position. The results of the repeated measures ANOVA demonstrated no significant differences in repositioning accuracy between the CLBP group and the healthy control group in either standing or seated positions. However, there was a significant difference between the standing and seated positions for the sample (p \u3c 0.05). Overall, for all subjects, the mean absolute repositioning error was greater in a seated position than in standing. In addition, the groups were no statistically different in TROM or baseline neutral positions in either standing or seated positions. To examine the difference in lumbar lordosis before and after neutral spine training, a single factor (time) repeated measures ANOVA was performed on the measurements obtained with the flexible ruler. There was a significant time effect for both the CLBP and control groups; the lumbar lordosis measures were significantly reduced with neutral spine posture. The between group effect was not significant. MANOVA indicated significant differences between the groups for trunk extension strength and abdominal strength. In both cases the CLBP group had statistically weaker trunk extension and trunk flexion strength

Exploring Low to Moderate Velocity Motor Vehicle Rear Impacts as a Viable Injury Mechanism in the Lumbar Spine

Epidemiological research suggests that up to 50% of individuals involved in low speed rear impact collisions develop acute onset low back pain. Given that little information is known about the low back injury mechanisms as a result of these collisions the overarching goal of this thesis was to explore low to moderate velocity rear-end collisions as a potential low back injury mechanism. Using a combination of data mining, in vivo and in vitro mechanical testing of porcine functional spinal units, the global purposes of this thesis were to (i) explore the types of low to moderate velocity collisions that frequently result in claims of low back pain and injury (ii) explore the influence of low velocity rear impact collisions on peak in vivo joint loading, occupant pain reporting and passive tissue response of the lumbar spine, and (iii) characterize the effects of these mechanical exposures and explore facet joint capsule injury as a potential source of injury and pain generating pathways following low to moderate severity impacts. In-line with these global purposes, four independent studies were conducted, each with their own focused objectives. Study I - Exploring Low Velocity Collision Characteristics Associated with Claimed Low Back Pain Background: Up to fifty percent of individuals involved in low to moderate velocity collisions report low back pain. However, our understanding of the specific collision or occupant characteristics that result in such claims of low back pain remains limited. Objectives: The primary objective of this study was to define the circumstances of low velocity motor vehicle collisions that result in litigation in Ontario with claims of low back injury. Methods: Data for this investigation were obtained from a forensic engineering firm based in Toronto, Ontario, Canada. The database was searched and only cases with an evaluation of the injuries sustained in passenger vehicle to vehicle collisions, with a collision severity of 24 km/hour or less were included in this analysis. Each identified case was reviewed for collision characteristics, pre-existing medical conditions and injuries claimed. Descriptive statistics (mean, SD and ranges) across low back injury claims were computed for documented variables. Results: Out the 83 cases reviewed, 77% involved a claim of low back injury. Specific to those who claimed low back injury, examination of the medical history revealed that pre-existing low back pain (LBP) or evidence of lumbar disc degeneration were particularly common with 63% of claimants either having had a history of LBP or evidence of lumbar disc degeneration, or both. Of all low back injury claims, 97% were accompanied by a whiplash and/or whiplash associated disorder claim. For low back injury claims, a rear-end impact was the most common configuration (70% of all low back injury claims involved a rear-end collision). The majority of all low back injury claimants experienced a change in velocity of 13 km/hour or less (69%), with 42% of all low back injury claims falling between collision severities of 10 – 12 km/hour. Conclusions: Results indicate that rear-end collision severities of 10 – 12 km/hour appear to be particularly common with respect to low back injury reporting; more severe collisions were not associated with greater low back injury reporting. This result contrasts with previously published neck injury risk data, which demonstrated the risk of neck injury symptom reporting increases with collision severity. Evidence of lumbar disc degeneration was particularly common across claimants with low back injury claims. Study II - Characterizing Trunk Muscle Activations During Simulated Low Speed Rear Impact Collisions Background: The internal forces generated by the musculature of the lumbar region create most of the mechanical load placed on the spine. Thus, despite the anticipated low external forces generated between the occupant and the automobile seatback during a low speed rear impact collision, increased muscle tension may influence the resultant peak joint loads experienced in the lumbar spine. Consequently, the risk of low back injury may be altered by muscle activation. Objective: The purpose of this study was to evaluate the activation profiles of muscles surrounding the lumbar spine during unanticipated and braced simulated rear-end collisions. Methods: Twenty-two low speed sled tests were performed on eleven human volunteers (△v = 4 km/h). Each volunteer was exposed to one unanticipated impact and one braced impact. Accelerometers were mounted on the test sled and participants’ low back. Six bilateral channels of surface electromyography (EMG) were collected from the trunk during impact trials. Peak lumbar accelerations, peak muscle activation delay, muscle onset time and peak EMG magnitudes, normalized to maximum voluntary contractions (MVC), were examined across test conditions. Results: While not statistically significant, bracing for impact tended to reduce peak lumbar acceleration in the initial rearward impact phase of the occupant’s motion by approximately 15%. The only trunk muscles with peak activations exceeding 10% MVC during the unanticipated impact were the thoracic erector spinae. Time of peak muscle activation was slightly longer for the unanticipated condition (unanticipated = 296 ms; braced = 241 ms). Conclusions: Results from this investigation demonstrate that during an unanticipated low speed rear-end collision, the peak activation of muscles in the lumbar spine are low in magnitude. As such, muscle activation likely has minimal contribution to the internal joint loads that are experienced in the lumbar intervertebral joints during low speed rear impact collisions. Study III - Characterizing In Vivo Mechanical Exposures of the Lumbar Spine During Simulated Low Velocity Rear Impact Collisions Background: Historically, there has been a lack of focus on the lumbar spine during rear impacts because of the perception that the automotive seat back should protect the lumbar spine from injury. As a result, there have been no studies involving human volunteers to address the risk of low back injury in low velocity rear impact collisions. Objectives: The primary objectives of this study were to explore lumbar kinematics and joint reaction forces in human volunteers during simulated rear impact collisions and to examine the influence of lumbar support on the peak motion and forces experienced in the lumbar spine. A secondary objective was to evaluate lumped passive stiffness changes and low back pain reporting after a simulated rear impact collision Methods: Twenty-four participants (12 male, 12 female) were recruited. A custom-built crash sled was used to simulate unanticipated rear impact collisions, with a change in velocity of approximately 8 km/h. Randomized collisions were completed with and without lumbar support. Measures of passive stiffness and flexion-relaxation-ratio (FRR) were obtained prior to impact (Pre), immediately post impact (Post) and 24 hours post impact (Post-24). LBP reporting was monitored over the next 24 hours leading up to the final Post-24 measures. For collision simulations inverse dynamics analyses were conducted, and outputs were used to generate estimates of peak L4/L5 joint compression and shear. From the passive trials, lumbar flexion/extension moment-angle curves were generated to quantify time-varying changes in the passive stiffness of the lumbar spine, Post and Post-24 relative to Pre. FRRs were computed as the ratio of thoracic erector spinae and lumbar erector spinae muscle activation in an upright posture to muscle activation in a flexed position Results: Average [± standard deviation] peak L4/L5 compression and shear reaction forces were not significantly different without lumbar support (Compression = 498.22 N [±178.0]; Shear = 302.2 N [± 98.5]) compared to with lumbar support (Compression = 484.5 N [±151.1]; Shear = 291.3 N [±176.8]). Lumbar flexion angle at the point of peak shear was 36 degrees [±12] without and 33 degrees [±11] with lumbar support, respectively, with 0 degrees being the lumbar posture in upright standing. No participants developed clinically significant levels of LBP after impact. Time was a significant factor for the length of the low stiffness flexion and extension zone (p = 0.049; p = 0.035), the length of the low stiffness zone was longer in the Post and Post-24 trial for low stiffness flexion and longer in the Post-24 for low stiffness extension. Conclusions: Findings demonstrate that during a laboratory-simulation of an unanticipated 8 km/hour rear-impact collision, young healthy adults do not develop LBP. Lumbar support did not significantly influence the estimated L4/L5 joint reaction forces. Changes in the low stiffness portion of the passive flexion/extension curves were observed following impact and persisted for 24 hours. Changes in passive stiffness may lead to changes in the loads and load distributions within the passive structures such as the ligaments and intervertebral discs following impacts. Study IV - Exploring the Interaction Effects of Impact Severity and Posture on Vertebral Joint Mechanics Background: To date, no in vitro studies have been conducted to explore lumbar soft tissue injury potential and altered mechanical properties from exposure to impact forces. Typically, after a motor vehicle collision, the cause of a reported acute onset of low back pain is difficult to identify with potential soft tissue strain injury sites including the facet joint and highly innervated facet joint capsule ligament (FCL). Objectives: The purpose of this investigation was to quantify intervertebral translation and facet joint capsule strain under varying postures and impact severities. A secondary objective was to evaluate flexion-extension and shear neutral zone changes pre and post impact. Methods: A total of 72 porcine cervical FSUs were included in the study. Three levels of impact severity (4g, 8g, 11g), and three postures (Neutral Flexion and Extension) were examined using a full-factorial design. Impacts were applied using a custom-built impact track which simulated impact parameters similar to those experienced in low to moderate speed motor vehicle collisions. Passive flexion-extension and shear neutral zone testing were completed immediately prior to and immediately post impact. Intervertebral translation and the strain tensor of the facet capsule ligament were measured during impacts. Results: A significant main effect (p > 0.001) of collision severity was observed for peak intervertebral translation and peak FCL shear strain (p = 0.003). A significant two-way interaction was observed between pre-post and impact severity for flexion-extension neutral zone length (p = 0.031) and stiffness (p>0.001) and anterior-posterior shear neutral zone length (p = 0.047) and stiffness (p>0.001). This was a result of increased neutral zone range and decreased neutral zone stiffness pre-post for the 11g severity impact (regardless of posture). Conclusions: This investigation provides evidence that overall the peak vertebral translations observed across 4g to 11g impacts are below previously published ultimate shear failure displacements. FSU’s exposed to the highest severity impact (11g) had significant NZ changes, with increases in joint laxity in flexion-extension and shear testing and decreased stiffness, suggesting that soft tissue injury may have occurred. Despite observed main effects of impact severity, no influence of posture was observed. This lack of influence of posture and small FCL strain magnitudes suggest that the FCL does not appear to undergo injurious or permanent mechanical changes in response to low to moderate MVC impact scenarios. Study V - Characterizing the Mechanical Properties of the Facet Joint Capsule Ligament Background: The facet joint capsule ligament (FCL) is a structure in the lumbar spine that constrains motions of the vertebrae. Previous work has demonstrated that under physiological motion the FCL is subjected to significant deformation with FCL strains increasing in magnitude with increasing flexion and extension moments. Thus, it is important to characterize the mechanical response of the FCL for investigations into injury mechanisms. Sub failure loads can produce micro-damage resulting in increased laxity, decreased stiffness and altered viscoelastic responses. Thus, the objective of this investigation was to determine the mechanical and viscoelastic properties of the FCL under various magnitudes of strain from control samples and samples that had been exposed to an impact. Objectives: The purpose of this investigation was to quantify the mechanical properties and viscoelastic response of control and impacted FCL. Methods: 200 tissue samples were excised from the right and left FCL of 80 porcine cervical functional spinal units (FSU’s). Tissue samples were excised from FSU’s obtained from Study 4. Twenty FCL tissue samples served as the control group. The remaining 180 FCL tissue samples were randomly obtained from FSU’s that had been exposed to one of nine impact conditions (impacted tissue). Each specimen was loaded uniaxially, collinear with the primary fiber orientation. The loading protocol was identical for all specimens: preconditioning with 5 cycles of loading/unloading to 5% strain, followed by a 30 second rest period, 5 cycles of 10% strain and 1 cycle of 10% strain with a hold duration at 10% strain for 240 seconds. The same protocol followed for 30% (cyclic-30% & 30%-hold) and 50% strain (cyclic-50% & 50%-hold). All loading and unloading were performed at a rate of 2%/sec. All impacted FCL properties were compared back to controls. Measures of stiffness, hysteresis and force-relaxation were computed for the 30% and 50% strain conditions. Results: No significant differences in stiffness were observed for impacted specimens in comparison to control (30% Control = 2.64 N/mm; 4 g = 2.20 N/mm, 8 g = 2.07 N/mm, 16 g = 2.16 N/mm)(50% Control = 5.06 N/mm; 4g = 4.60 N/mm, 8 g = 4.07 N/mm, 16 g =4.64 N/mm). Impacted specimens from the 8g Flexed and 11 g Flexed and Neutral conditions exhibited greater hysteresis during the cyclic-30% and cyclic-50%, in comparison to controls. In addition, specimens from the 8g and 11g Flexed conditions resulted in greater force relaxation for the 50%-hold conditions. Conclusions: Results from this study demonstrate viscoelastic changes in FCL samples exposed to moderate and highspeed impacts in the flexed posture. However, it is interesting that these viscoelastic changes were not accompanied by changes in stiffness. Findings from this investigation provide novel insight and provide mechanical and viscoelastic properties of the FCL both in control and impacted scenarios. Global Summary: Findings from this thesis demonstrate that (i) rear-end collision severities of 10 – 12 km/hour appear to be particularly common with respect to low back injury reporting (ii) during a laboratory-simulation of an unanticipated 8 km/hour rear-impact collision, young healthy adults do not develop LBP, however, changes in the low stiffness portion of the passive flexion/extension curves were observed following impact and persisted for 24 hours and (iii) the observed peak displacements in porcine functional spinal units exposed to varying impact severities are below ultimate shear failure displacements and does not support a lumbar spine injury mechanism resulting in acute traumatic bone fractures and/or acute traumatic IVD herniations in previously “healthy” tissues. Overall, the small FCL strain magnitudes during impacts and unchanged FCL mechanical properties post-impact suggest that the FCL does not undergo injurious or permanent mechanical changes in response to low to moderate MVC impact scenarios. Collectively, the findings from this thesis indicate that there are no direct mechanical changes that would indicate the high incidence of low back pain reporting following low to moderate severity rear-end motor vehicle impacts. However, changes in passive tissue properties were observed, and if persistent over time, may predispose individuals to secondary pain pathways. It is also important to note that this thesis tested healthy conditions and the results do not directly apply to pre-existing LBP cases being exposed to the same impacts

Low back pain in schoolgirl rowers: Prevalence, bio-psycho-social factors and prevention

Rowing is one of the largest participant sports on the Independent Girls‟ Schools Sporting Association (IGSSA) in Western Australia with approximately 400 participants competing every year. Rowing is an extra-curricular sport offered to girls 14 years of age and above, with these girls competing and training in both sweep and scull boats. Whilst the benefits of regular physical activity and exercise are well known, musculoskeletal problems have been documented in rowing. In particular, clinical evidence and previous research suggests that low back pain (LBP) is common in rowers. Adolescents who suffer from LBP are at an increased risk of recurrent and chronic LBP during adulthood therefore, this is a critical period to investigate the development of LBP. Therefore, the aim of this doctoral research was to examine LBP amongst the IGSSA rowing population in Western Australia. As the aetiology of LBP is known to be multi-factorial, the problem was investigated from a bio-psycho-social perspective. This thesis contains three studies with data collected over a two year period. These studies are described below. In the first study, an investigation of the incidence of LBP and the levels of LBP and LBP-related disability for rowers and non-rowers was undertaken. Scoping data on self-reported factors that “bring on” or exacerbate LBP, training hours completed per week and boats most frequently rowed in was also collected in rowers. From this study, it was identified that there was a significantly higher prevalence of LBP in the group of 356 Schoolgirl rowers when compared with 496 non-rowing controls. Further, there was a significant difference evident for pain incidence between Year 9 and Year 10 rowers. Rowers also showed significantly greater pain and disability scores when compared with non-rowers. A number of self-reported rowing-related and habitual factors were associated with LBP in rowers. The second study of this thesis investigated a sub-sample of Schoolgirl rowers from the first study. Specifically, rowers with LBP (N=30) and without LBP (N=30) participated in a cross-sectional study to determine the physical and psycho-social variables associated with LBP. In addition to measuring the levels of pain and disability in the rowers, this study examined physical factors such as static lumbo-pelvic postures, spinal proprioception, isometric back and lower limb muscle endurance, joint hypermobility, and the psycho-social factors of beliefs about back pain, fear of movement with back pain, as well as the tendency for anxious and depressed behaviour. A secondary aim of the study was to classify the patterns of motor control impairment evident in those with LBP. The majority of the rowers were clinically classified with deficits in flexion or multi-directional segmental spinal control. Factors associated with LBP were reduced lower limb and back muscle endurance, and a general pattern for less accuracy and greater variability in lumbar spine repositioning sense. In the final study of this thesis a non-randomised controlled trial was conducted to decrease the prevalence of LBP and associated levels of pain and disability in a group of Schoolgirl rowers. In this novel study an intervention group consisting of 90 schoolgirl rowers from one school and a control group consisting of 131 participants from three other schools were recruited. The multi-dimensional intervention strategy consisted of physiotherapy screening, prescription of individualised “specific exercise”, follow up sessions, a back pain education talk and off-water strength and conditioning sessions. Primary outcome variables were collected for both the intervention and control groups at the commencement of rowing training, midway through the rowing season, at the completion of the rowing season and three months after the season had concluded. Primary outcome variables included the incidence of LBP and related levels of pain and disability whilst secondary outcome variables from the bio-psycho-social domain were measured at the start of the season and the end of the season in the intervention group only. From this study it was concluded that rowers have a high incidence of LBP but a multi-dimensional intervention program can be implemented to decrease the LBP incidence and the associated levels of pain and disability. Several secondary outcome variables considered to be of importance in LBP also significantly improved including physical fitness (aerobic conditioning, lower limb and back muscle endurance and sit and reach flexibility) and seated posture (usual and slump sitting). Further, improvements were seen in scores from the Child Behaviour Checklist. This doctoral thesis has investigated a real world problem and has subsequently been used to formulate policy amongst the IGSSA schools in Western Australia. Further research is needed to determine the respective long-term results with respect to LBP and further randomised controlled studies are required to further validate the findings