The influence of patellofemoral pain on muscle coordination, segment coordination, and segment coordination variability in runners

Management of patellofemoral pain syndrome (PFPS) remains a significant challenge in clinical practice and there is a need to understand the mechanisms for altered gait and muscular function which may lead to poor patient outcomes. The overall aim of the three studies in this dissertation was to determine if runners with current PFPS adapt their gait and muscle activation as a result of long-term, daily pain and/or in response to an acute pain flare and exertion during a moderate intensity 21-minute treadmill run compared to healthy controls. In addition, a resolved, asymptomatic PFPS group was included to investigate potential mechanisms for the frequent reoccurrence of pain experienced by those with a history of PFPS. The lack of differences in baseline kinematic, segment coordination, and segment coordination variability measures suggest that there are no long-term gait adaptations to pain in either injury group that manifest as resultant gait patterns. Several differences were identified in baseline kinetics among all three groups for peak hip abduction and external rotation as well as ankle inversion moments. These findings indicate that: 1) runners with a history of PFPS have different loading patterns at the hip and ankle compared to healthy runners and 2) these altered loading patterns are not substantial enough to alter resultant kinematic patterns of movement. In addition to these joint moments, altered muscle coordination discriminated between all three groups. These findings have significant implications for identifying individuals at risk of re-injury and helping to improve treatment efficacy in runners with PFPS. Movement evoked pain is a primary characteristic of PFPS, and the treadmill run used in these studies was sufficient to cause a pain response in the injured group. Changes seen in the outcome measures of the three studies at the end of the run are indicative of a response to a combination of increased pain and exertion. Greater anti-phase motion of the sagittal thigh-transverse shank in the injured group compared to controls suggests that altered movement control about the knee may be related to increased pain in those with PFPS. In addition to the decreased coordination variability observed in those with PFPS, there were also differences in coordination variability between the resolved and control groups, with the resolved group often showing increases in variability compared to controls. This suggests that abnormal movement flexibility may persist even once painful symptoms are resolved and that individuals with a history of PFPS do not return to healthy gait patterns following resolution of symptoms

Biomechanical, muscle activation and clinical characteristics of chronic exertional compartment syndrome

Chronic exertional compartment syndrome (CECS) is a common problem within both military and athletic populations that can be difficult to diagnose. Furthermore, it is unclear what causes the development of CECS, particularly in the military population, as personnel undertake a variety of activities that can cause pain with CECS such as fast walking, marching and running. Chronic exertional compartment syndrome has been hypothesised to develop due to excessive muscle activity, foot pronation and abnormal biomechanics predominantly at the ankle. Treatment of CECS through running re-education to correct these abnormalities has been reported to improve symptoms. However no primary research has been carried out to investigate the biomechanical, muscle activation and clinical characteristics of military patients with CECS. The purpose of this thesis was to provide an original contribution to the knowledge through the exploration of these characteristics; and the development of insights into the development of CECS, with implications for prevention and treatment. Study one investigated the clinical characteristics of 93 service personnel with CECS. Plantar pressure variables, related to foot type and anterior compartment muscle activity, and ankle joint mobility were compared during walking between 70 cases and 70 controls in study two. Study three compared three-dimensional whole body kinematics, kinetics and lower limb muscle activity during walking and marching between 20 cases and 20 controls. Study four compared kinematics and lower limb muscle activity during running in a separate case-control cohort (n=40). Differences in electromyography (EMG) intensity during the gait cycle were compared in the frequency and time domain using wavelet analysis. All studies investigated subject anthropometry. Cases typically presented with bilateral, ‘tight’ or ‘burning’ pain in the anterior and lateral compartments of the lower leg that occurred within 10 minutes of exercise. This pain stopped all cases from exercising during marching and/or running. As such subsequent studies investigated the biomechanics of both ambulatory and running gaits. Cases in all case-control studies were 2-10 cm shorter; and were typically overweight resulting in a higher body mass index (BMI) than controls. There was strong evidence from study 3 that cases had greater relative stride lengths than controls during marching gait. This was achieved through an increase in ankle plantarflexion during late stance and a concomitant increase in the gastrocnemius medialis contraction intensity within the medium-high frequency wavelets. Given the differences in height observed, this may reflect ingrained alterations in gait resulting from military training; whereby all personnel are required to move at an even cadence and speed. These differences in stride length were also observed in walking and running gaits although to a lesser extent. There was no evidence from the EMG data that cases had greater tibialis anterior activation than controls during any activity tested, at any point in the gait cycle or in any frequency band. In agreement, there was also no evidence of differences between groups in plantar pressure derived measures of foot type, which modulate TA activity. Toe extensor - related plantar pressure variables also did not differ between groups. In summary, contrary to earlier theories, increased muscle activity of the anterior compartment musculature does not appear to be associated with CECS. The kinematic differences observed during running only partially matched the clinical observations previously described in the literature. Cases displayed less anterior trunk lean and less anterior pelvic tilt throughout the whole gait cycle and a more upright shank inclination angle during late swing (peak mean difference 3.5°, 4.1° and 7.3° respectively). However, no consistent differences were found at the ankle joint suggesting that running is unlikely to be the cause of CECS in the military; and that the reported success of biomechanical interventions may be due to reasons other than modifying pathological aspects of gait. In summary, the data presented in the thesis suggest that CECS is more likely to develop in subjects of shorter stature and that this is associated with marching at a constant speed and cadence. Biomechanical interventions for CECS, such as a change in foot strike or the use of foot orthotics, are unlikely to be efficacious for the military as personnel will continue to be required to march at prescribed speeds to satisfy occupational requirements. Preventative strategies that allow marching with a natural gait and/or at slower speeds may help reduce the incidence of CECS. The lack of association with foot type or muscle activity suggests that foot orthoses would not be a useful prevention strategy or treatment option for this condition.Headley Court Trustees - funding of student fee

Characteristics of muscle activation patterns at the ankle in stroke patients during walking.

Stroke causes impairment of the sensory and motor systems; this can lead to difficulties in walking and participation in society. For effective rehabilitation it is important to measure the essential characteristics of impairment and associate these with the nature of disability. Efficient gait requires a complex interplay of muscles. Surface electromyography(sEMG) can be used to measure muscle activity and to observe disruption to this interplay after stroke. Yet, classification of this disruption in stroke patients has not been achieved. It is hypothesised that features identified from the sEMG signal can be used to classify underlying impairments. A clinically viable gait analysis system has been developed, integrating an in-house wireless sEMG system synchronised with bilateral video and inertial orientation sensors. Signal processing techniques have been extended and implemented, appropriate for use with sEMG. These techniques have focussed on frequency domain features using wavelet analysis and muscle activation patterns using principal component analysis. The system has been used to measure gait from stroke patients and un-impaired subjects. Characteristic patterns of activity from the ankle musculature were defined using principal component analysis of the linear envelope. Patients with common patterns of tibialis anterior activity did not necessarily share common patterns of gastrocnemius or soleus activity. Patients with similar linear envelope patterns did not always present with the same kinematic profiles. The relationship between observable impairments, kinematics and sEMG is seen to be complex and there is therefore a need for a multidimensional view of gait data in relation to stroke impairment. The analysis of instantaneous mean frequency and time-frequency has revealed additional periods of activity not obvious in the linear or raw signal representation. Furthermore, characteristic calf activity was identified that may relate to abnormal reflex activity. This has provided additional information with which to group characteristic muscle activity. An evaluation of the co-activation of gastrocnemius and tibialis anterior muscles using a sub-band filtering technique revealed three groups; those with distinct co-activation, those with little co-activation and those with continuous activity in the antagonistic pair across the stride. Signal features have been identified in sEMG recordings from stroke patients whilst walking extending current signal processing techniques. Common features of the sEMG and movement have been grouped creating a decision matrix. These results have contributed to the field of clinical measurement and diagnosis because interpretation of this decision matrix is related to underlying impairment. This has provided a framework from which subsequent studies can classify characteristic patterns of impairment within the stroke population; and thus assist in the provision of rehabilitative interventions

Computational Intelligence in Electromyography Analysis

Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG may be used clinically for the diagnosis of neuromuscular problems and for assessing biomechanical and motor control deficits and other functional disorders. Furthermore, it can be used as a control signal for interfacing with orthotic and/or prosthetic devices or other rehabilitation assists. This book presents an updated overview of signal processing applications and recent developments in EMG from a number of diverse aspects and various applications in clinical and experimental research. It will provide readers with a detailed introduction to EMG signal processing techniques and applications, while presenting several new results and explanation of existing algorithms. This book is organized into 18 chapters, covering the current theoretical and practical approaches of EMG research

Intelligent Biosignal Processing in Wearable and Implantable Sensors

This reprint provides a collection of papers illustrating the state-of-the-art of smart processing of data coming from wearable, implantable or portable sensors. Each paper presents the design, databases used, methodological background, obtained results, and their interpretation for biomedical applications. Revealing examples are brain–machine interfaces for medical rehabilitation, the evaluation of sympathetic nerve activity, a novel automated diagnostic tool based on ECG data to diagnose COVID-19, machine learning-based hypertension risk assessment by means of photoplethysmography and electrocardiography signals, Parkinsonian gait assessment using machine learning tools, thorough analysis of compressive sensing of ECG signals, development of a nanotechnology application for decoding vagus-nerve activity, detection of liver dysfunction using a wearable electronic nose system, prosthetic hand control using surface electromyography, epileptic seizure detection using a CNN, and premature ventricular contraction detection using deep metric learning. Thus, this reprint presents significant clinical applications as well as valuable new research issues, providing current illustrations of this new field of research by addressing the promises, challenges, and hurdles associated with the synergy of biosignal processing and AI through 16 different pertinent studies. Covering a wide range of research and application areas, this book is an excellent resource for researchers, physicians, academics, and PhD or master students working on (bio)signal and image processing, AI, biomaterials, biomechanics, and biotechnology with applications in medicine

Foot Kinematics and Neuromuscular Preactivation in Habitual Forefoot and Rearfoot Runners

As the rate of running related injuries has failed to decline despite advances in footwear, many researchers have begun focusing on different foot strike patterns possible contribution to injury risk. While many studies have focused on the differences between RFS and FFS running, few have investigated kinematic differences within the distal foot in habitual RFS and FFS runners and have failed to consider mechanical and neuromuscular changes due to fatigue. The purpose of this study, therefore, was to investigate foot kinematics and neuromuscular differences between RFS and FFS runners at the beginning and end of an exhaustive run. Fifteen habitual RFS and 15 habitual FFS runners (27.6 ± 5.64 years) performed a maximal 5 km treadmill run. A seven segment foot model was used with 3D motion capture methods to calculate joint kinematics of six functional articulations: rearfoot, calcaneonavicular, calcaneocuboid, medial forefoot, lateral forefoot, and first metatarsophalangeal (MTP). Four dual Ag/AgCl EMG surface electrodes were attached to the medial gastrocnemius, peroneus longus, soleus, and tibialis anterior to identify neuromuscular activity. Motion capture and EMG data were analyzed for five consecutive steps at the beginning and end of the 5 km run. Motion capture data was processed to investigate foot kinematic and joint coordination variability differences between the foot strike patterns at the beginning and end of the 5 km run. EMG data was processed to investigate neuromuscular preactivation onset and magnitude (iEMG) differences between the foot strikes at the beginning and end of the run. Mixed between-within groups statistical tests were used to compare variables between the foot strike patterns at the beginning and end of the exhaustive run. Exploration of kinematic results indicated a more supinated foot in FFS runners at initial contact and through early stance. The increased foot supination may result in a more rigid foot, but a less stable ankle joint. When the foot is moving toward greater pronation, a greater demand on soft tissues for stability is expected which may imply increased risk of soft tissue injury within the foot for RFS runners. Both groups demonstrated an increased range of motion at the end of the run during the first (0-20% of stance), 3rd (51-75% of stance), and 4th (76-100% of stance) stance subphases which may be a result of muscular fatigue and may increase injury risk to dynamic stabilizers of the foot articulations. With respect to joint coordination, rearfoot-midfoot coupling variability increased in both groups during midstance (21-50% of stance) at the end of the run. The increased variability may have been indicative of neuromuscular compensation to alter step-to-step variability in order to avoid overstressing tissues which may lead to overuse injury. Neuromuscular preactivation magnitude was increased and occurred earlier in the tibialis anterior in RFS runners and preactivation onset was earlier in the gastrocnemius in FFS runners. While RFS runners require tibialis anterior activation to maintain a dorsiflexed position at initial contact, it is likely that the earlier gastrocnemius onset in FFS runners facilitates positioning of the foot for initial contact with the forefoot. The earlier gastrocnemius onset in FFS with no significant difference in magnitude may suggest different roles of the gastrocnemius between the foot strikes and may be clinically relevant when looking at overuse injury risks. There was no difference in neuromuscular preactivation as a result of the 5 km run, suggesting that neuromuscular fatigue did not affect how the muscles prepared for initial contact

On the quantification and objective classification of instability in the healthy, osteoarthritic and prosthetic knee

Knee instability is a common complaint in osteoarthritis (OA), and a common reason for revision following total knee arthroplasty (TKA). Despite this, assessment of instability is hampered by the lack of a validated method of objective classification or quantification, with most research relying upon patient reports of frequency of symptoms. The aim of this thesis is to define a theoretical framework for instability in the knee, and to develop a protocol for the classification and quantification of instability in the native and prosthetic knee. Instability of the knee in this thesis is understood as the failure of the joint to return to a zero-state following perturbation using all the available active and passive mechanisms available to it, resulting in system collapse. Symptomatic instability is the awareness of reaching the boundary between the stable and unstable state. The prevalence of subjective instability in the end stage OA knee was measured from a publicly available database of pre-operative knee scores from TKA patients, while the prevalence of instability as a cause of revision was assessed from case note review of TKA revision patients from a tertiary referral orthopaedic unit. A single channel, tibia mounted accelerometer was selected for assessment of frontal plane knee movement during normal walking and a protocol developed its use. This was assessed for its repeatability and compared with standard gait analysis in healthy volunteers, and subjectively stable and unstable post-operative TKA patients. Found to be repeatable with differentiation of output between subjectively stable and unstable TKA, the protocol was adapted and used to compare subjectively stable and unstable OA knees prior to TKA. Using patient subjective assessment as classifier, wavelet transforms, Principal Component Analysis and linear regression was used to produce a classification model from the accelerometer data. The single accelerometer was found to produce classification with an accuracy of 84.6%, sensitivity of 93.3% and specificity of 72.7%, with area under the curve (AUC) of 0.797. This classification model for instability produces the basis from which the protocol can be adapted and developed to improve performance and ultimate quantify instability in the knee for use in clinical and research settings.Knee instability is a common complaint in osteoarthritis (OA), and a common reason for revision following total knee arthroplasty (TKA). Despite this, assessment of instability is hampered by the lack of a validated method of objective classification or quantification, with most research relying upon patient reports of frequency of symptoms. The aim of this thesis is to define a theoretical framework for instability in the knee, and to develop a protocol for the classification and quantification of instability in the native and prosthetic knee. Instability of the knee in this thesis is understood as the failure of the joint to return to a zero-state following perturbation using all the available active and passive mechanisms available to it, resulting in system collapse. Symptomatic instability is the awareness of reaching the boundary between the stable and unstable state. The prevalence of subjective instability in the end stage OA knee was measured from a publicly available database of pre-operative knee scores from TKA patients, while the prevalence of instability as a cause of revision was assessed from case note review of TKA revision patients from a tertiary referral orthopaedic unit. A single channel, tibia mounted accelerometer was selected for assessment of frontal plane knee movement during normal walking and a protocol developed its use. This was assessed for its repeatability and compared with standard gait analysis in healthy volunteers, and subjectively stable and unstable post-operative TKA patients. Found to be repeatable with differentiation of output between subjectively stable and unstable TKA, the protocol was adapted and used to compare subjectively stable and unstable OA knees prior to TKA. Using patient subjective assessment as classifier, wavelet transforms, Principal Component Analysis and linear regression was used to produce a classification model from the accelerometer data. The single accelerometer was found to produce classification with an accuracy of 84.6%, sensitivity of 93.3% and specificity of 72.7%, with area under the curve (AUC) of 0.797. This classification model for instability produces the basis from which the protocol can be adapted and developed to improve performance and ultimate quantify instability in the knee for use in clinical and research settings