http://hdl.handle.net/10397/41 Search the Channel search http://repository.lib.polyu.edu.hk/jspui/simple-search http://hdl.handle.net/10397/5720 Title: An interactive physio-psychological model on understanding stress among individuals performing sedentary computer tasks<br/><br/>Authors: Wang, Yuling<br/><br/>Abstract: Modern day people commonly suffer from musculoskeletal disorders associated with intensive computer use, which has many important physical and mental risk factors. The overall purpose of this thesis was to investigate the acute physiological and psychosocial responses exposed to stress-induced workloads among computer users with and without neck pain. A pilot study and a main study were conducted to explore the effects of different combinations of physical and mental workloads using different forms of computer tasks in order to produce stress-induced responses in different body systems. The pilot study examined the effects of physical and mental workload in three computer tasks on muscle activity and cardiovascular measures. Fourteen healthy, pain-free adults (7 males and 7 females, mean age = 23.72 ± 3.0 yrs) were asked to complete three tasks of 15 minutes each. The tasks were (1) copy-typing ("typing"), (2) typing at progressively faster speeds ("pacing"), and (3) mental arithmetic plus fast typing ("subtraction"). Median muscle activity (50th percentile amplitude probability distribution function) was examined in 5-minute intervals during each task and each rest period, and statistically significant differences in the time factor (within task) and time × task factors were found in the bilateral cervical erector spinae (CES) and upper trapezius (UT) muscles. In contrast, distal forearm muscle activities (extensor carpi radialis and flexor carpi ulnaris) did not show any significant differences among the three tasks. Heart rate (HR) and blood pressure (BP) showed significant differences during tasks compared to baseline, and diastolic blood pressure (DBP) was significantly higher in the subtraction task than in the pacing task. The results suggest that cervical postural muscles had higher reactivity than forearm muscles to high mental workload tasks. Cervical muscles were also more reactive to tasks with high physical demand than high mental demand. HR and BP seemed to respond similarly to high physical and mental workloads.; The aims of the main study were to investigate the responses of the objective measures in the muscular system, neurophysiological system, and cardiovascular system. The physiological markers included surface electromyography (EMG), electroencephalography (EEG), heart rate variability (HRV), HR, and BP. In addition to these physiological measurements, subjective responses were recorded in terms of rate of perceived exertion (RPE), anxiety, and discomfort. The behavioral performance measures included the number of total trials and the accuracy of completed Stroop trials. In the main study, 46 adult university students, with 22 males and 24 females (mean age = 23.7 ± 3.7 years). All participants were categorized into the Pain-Free Group (n = 23) or the Neck Pain Group (n = 23). Each participant was required to perform five tasks: Task 1, a self-paced copy-typing task; Task 2, a fast copy-typing task; Task 3, a fast copy-typing CWT; Task 4, a verbal CWT; and Task 5, a prolonged CWT using a standardized computer workstation. The overall results indicated that the combined high-physical and high-mental workloads elicited consistent trends of greater increases in activity of various physiological measures compared to high-physical or high-mental workloads alone. Brain activity seemed to be more sensitive in response to all three types of workload variation, whereas muscular activity seemed to be more responsive to physical workload or physical-plus-mental workload. HRV showed more variable response patterns, especially in the Neck Pain Group compared to Pain-Free Group. The effects of sustained high-physical and high-mental demands (Task 5) produced similar but more exaggerated responses in various systems. While these physiological changes within the body systems occurred largely in similar directions of change in both groups of participants, the Neck Pain Group experienced significant increases in feelings of discomfort and anxiety, whereas the Pain-Free Group did not. The increased symptom scores in the symptomatic group were also accompanied by poorer behavioral performance, with fewer total completed trials, fewer correct trials, and longer response time in the Stroop task. In conclusion, the study confirms the important association between physiological and psychosocial responses in people with and without neck pain. The results also support the phenomenon that individuals with chronic pain have pain-related cognitive impairment and maladaptive physiological responses. However, this study cannot confirm any cause-and-effect relationship between these mechanisms due to its cross-sectional study design. Extensive research needs to be continued to further understand the inter-relationship between physical and mental stress factors in the human body.<br/><br/>Description: xxiii, 227, 33, 19 leaves : ill. ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577P RS 2012 Wang http://hdl.handle.net/10397/5719 Title: Differential effects of memory encoding : differentiation between perceptual and semantic processing<br/><br/>Authors: Kuo, Chih Chien Michael<br/><br/>Abstract: In this thesis, the neural mechanisms of perceptual and semantic encoding of younger, older adults and people with mild cognitive impairment (MCI) were investigated using subsequent memory effect (SME). The SMEs were taken from ERPs of subsequently correctly identified trials and missed trials in study-test intentional recognition experiments. Study 1: This study investigated the differentiation between subsequent memory effects associated with successful encoding in perceptual and semantic encoding tasks. Single Chinese characters were used in both encoding tasks. Seventeen healthy young participants (6 male) participated in the study. Their mean age was 21.5±2.3 (range 19 to 28) years and they received an average 14.7±1.1 (range 13 to 16) years of education. Participants first learnt names of objects represented by single Chinese characters in two encoding tasks: inspecting their orthographic components (perceptual) and deciding the objects can or cannot make sounds (semantic). After each encoding task, participants performed a recognition task. The recognition task involved the participants to indicate whether the single characters shown were studied or unstudied. Results showed that the participants were significantly more accurate (in terms of d-prime measure) in identifying the studied characters in the semantic than perceptual condition (1.97±0.58 vs. 2.30±0.71, p<0.05) while there was no difference in reaction times. In both conditions, the SMEs were more positive-going waveforms for the correctly identified trials than missed trials and significant in windows between 120 and 240 ms (P2), 240 and 360 ms (N3), 360 and 700 ms (P550), and 700 and 1000 ms (late positive component; LPC). SME of P2 has been suggested to be related to working memory or attentional operations, SME of N3 to conceptual processings, and SME of P550 and LPC to elaborative processings. Their LPCs, rather than earlier components, were found to moderately correlate with the performances (accuracy) on the task. Semantically-learnt characters elicited LPC with significantly greater amplitudes over the frontal pole regions; Perceptually-learnt elicited larger SME in the central sites. The significant SME in the frontal regions in both conditions suggests that the coordination and incorporation of the orthographic information into mental representation was essential to both task conditions. While larger central effect in the perceptual condition may indicate perceptual processing that enhance memorabiltiy of an item, underlying processes expressed by frontal pole SME as shown in the semantic condition might be important for strategic operations that can further enhance encoding. Differences in SMEs of P2 and N3 between conditions were also found to be significant. Probable explanations for these SMEs were discussed. Study 2: Elderly adults may show significant SMEs with both perceptual and semantic type of encoding tasks but previous findings were mainly drawn from investigations in which the two tasks were not evaluated together. Simultaneous assessment of both tasks in the elderly have only been conducted by Friedman and colleagues (1996) using atypical stem completion and cue recall tests at retrieval. Stem completion is considered an indirect memory test and their behavioural results from cued recall test suggested older participants might have used an implicit retrieval strategy, which may also explain why they failed to find reliable SMEs in older adults when learning perceptually and semantically. Therefore, this study adopted the similar paradigm established in Study 1 and investigated age-related SME difference in performing perceptual and semantic tasks with a more appropriate recognition test. Seventeen healthy young adults from Study 1 and 17 healthy elderly adults (HEA; 10 male) were included in the study. HEA's mean age were 65.3±4.9 (range 58 to 76) years and they received an average 8.9±4.0 (range 3 to 21) years of education. Results of the HEA were largely consistent with previous findings that used a recognition test. In this study, it was found that younger adults performed better than the elderly in both conditions. Semantic orientation helped older adults to perform better than a perceptual task as indicated by d’ measure (0.75±0.42 vs. 1.34±0.71, p=0.004). Significant SME were found in P2 and N3 windows in both conditions and P550 window in the semantic condition in the HEA. SME in LPC was not significant but correlation analysis still indicated positive correlation between SME amplitude and d’ measure in each condition. When semantic processing was required, ERP differences in earlier windows (P2, N3, and P550) were less evident between the younger adult and HEA groups. It is not till the LPC window that more definite age-related differences were found. In the perceptual condition, however, differences were already shown at P550 window, suggesting older people might have more difficulty performing perceptual processing to result in successful encoding. Standardized low-resolution brain electromagnetic tomography (sLORETA) images and topography analysis suggested that, in the perceptual condition, both groups seemed to rely on similar frontal-parietal networks. However, the older group's difficulty in perceptual encoding may be due to a failure to recruit further PFC in the LPC window. In the semantic condition, it appeared that older adults might have inefficient frontal-temporal network for encoding information. This may also be because a compensatory mechanism was not sufficient to equalise memory performance.<br/><br/>Description: xxiii, 168 leaves : ill. ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577P RS 2012 Kuo http://hdl.handle.net/10397/5718 Title: An innovative assessment of the biomechanical properties of plantar tissues and diabetic foot ulcers<br/><br/>Authors: Chao, Yuet Lan Clare<br/><br/>Abstract: Foot ulcers are a common complication of diabetes mellitus and the predisposing factors are multifactorial. Diabetic peripheral neuropathy and repetitive stress are the most well known causative factors for diabetic related foot injuries while microvascular dysfunction is throught to be an essential factor contributing to the pathogenesis of tissue breakdown in the diabetic foot. It may also play a role in the development of neuropathy and interact with the complex interchange of advanced glycosylation end products as induced by hyperglycaemia, causing potential pathological consequences of morphological change in skin and soft tissue properties. Yet the precise mechanism of this process remains unclear. Apart from the pathological changes that take place in plantar skin morphology, foot swelling and changes in the properties of plantar soft tissues may further increase the risk of foot ulceration in people with diabetes. In order to develop strategies to prevent or manage diabetic ulcers, it is vital to obtain a better understanding of the underlying pathophysiology of diabetic ulcers. Also, a precise and quantitative method for evaluating the healing of ulcers is essential for making appropriate treatment decisions and monitoring the efficacy of the treatments. Thus far, a precise quantitative method of assessing wound healing or the properties of ulcer tissues is lacking. The restoration of the mechanical properties of wound tissue is an important indicator of the quality of wound healing. Nonetheless, changes in the biomechanical properties of skin wound tissues across different phases of the wound healing process have not been explored. In laboratory work, the evaluation of wound tissue properties can be achieved by testing an excised wound specimen using Material Testing Systems in vitro. An optical coherence tomography (OCT)-based air-jet indentation system is a novel non-contact method that has been recently developed for characterizing the biomechanical properties of soft tissues in a non-contact way. It can potentially be used for assessing the properties of wound tissues in vivo. This project consists of four inter-related studies, with each study having specific objectives. They are: (I) The epidermal thickness and biomechanical properties of plantar tissues in the diabetic foot; (II) The association between skin blood flow and oedema on epidermal thickness in the diabetic foot; (III) A novel non-contact method to assess the biomechanical properties of wound tissue in humans; (IV) In vivo and in vitro approaches to studying the biomechanical properties of healing wounds in rat skin.; Study I: The objective of Study I was to examine the morphological changes in plantar epidermal thickness and in the properties of the soft tissues of the diabetic foot in humans. Method and result of Study I: Seventy-two people with diabetes, namely 22 people with neuropathies, 16 with foot ulcerations, 34 with diabetics but without complications; and 40 healthy controls participated in the study. The thickness of the epidermal layer of the plantar skin was examined using high-frequency ultrasonography. Using the Tissue Ultrasound Palpation System, the thickness and stiffness of the total plantar soft tissue were measured at the big toe, the first, third, and fifth metatarsal heads, and the heel pad. As compared with the control group, the average epidermal thickness of plantar skin decreased by 15% in people with diabetic foot ulcerations and 9% in people with neuropathy, but increased by 6% in those with diabetes without complications. An 8% increase in the total thickness of the plantar soft tissues was observed in all diabetic subjects at all testing sites (all p<0.05), with the exception of the first metatarsal head. The stiffness of the plantar soft tissues increased in all diabetic groups at all testing sites as compared with the control group (all p<0.05). Study II: The aim of this study was to explore the association of skin blood flow and oedema on epidermal thickness in the feet of people with and without diabetes. Eighty-seven subjects, namely 19 people with diabetic neuropathy and foot ulcerations, 35 people with diabetes but without neuropathy, and 33 non-diabetic healthy controls participated in the study. High-frequency ultrasonography was used to measure the epidermal thickness and oedema in the papillary skin of the big toe as reflected by the thickness of the subepidermal low echogenic band (SLEB). The capillary nutritive blood flow was measured by the use of video capillaroscopy and skin blood flux was monitored by laser-Doppler flowmetry. We demonstrated that the thickness of the SLEB had increased in all diabetics, to a greater extent in people with neuropathy and ulceration than those without (64.7% vs 11.8%, p<0.001). Skin blood flux was shown to be higher in the groups with diabetes than in the controls (all p<0.05), but no significant difference was found in the resting nutritive capillary blood flow (p>0.05). A significant fair negative correlation (p=0.002, r=-0.366) was demonstrated between the SLEB and epidermal thickness at the pulp of the big toe, while no significant correlations were found among capillary blood flow, skin blood flux, and epidermal thickness (all p>0.05). Study III: This study evaluated the stiffness of diabetic foot ulcer tissues and examined the test-retest reliability of the newly developed OCT-based air-jet indentation system for characterizing the biomechanical properties of wound tissues in humans. Eight subjects with diabetes (7 males, 1 female) participated in the study, and a total of 10 foot ulcers were assessed. Twenty measuring sites located either at the central wound bed (n=10) or in periulcer areas (n=10) were identified and their biomechanical properties were assessed by the use of the air-jet indentation system. The test-retest reliability was examined at all measuring points. We found that the average stiffness of the peri-ulcer area (0.47 ± 0.15 N/mm) was significantly higher than that of the central wound bed area (0.35 ± 0.23 N/mm; p=0.042). Excellent test/retest reliability was demonstrated (ICC: 0.986; Pearson’s correlation: r=0.972, p<0.001). Study IV: This study examined the biomechanical properties of healing skin wounds in vivo using an air-jet indentation system and in vitro using a conventional material testing system in a rat model. Thirty male Sprague-Dawley rats, each with a 6 mm full-thickness circular punch biopsied wound at each posterior hind limb, were used. The stiffness at both the wound central and the margins was measured repeatedly in five rats at the same wound sites to monitor the longitudinal changes over various wound healing phases (i.e., before wounding, and on Days 0, 3, 7, 10, 14, and 21 after wounding) in vivo using an OCT-based air-jet indentation system. In addition, five rats were euthanized at each time point, and the biomechanical properties of the wound tissues were assessed in vitro using a material testing system. The size of the wound shrank significantly in the initial few days, closing almost completely by Day 10. At the central wound bed region, the stiffness at the baseline pre-wounding stage was 16.9 ± 2.2 N/m, which increased significantly from Day 0 (19.8 ± 5.3 N/m, 17.16%) and reached its peak on Day 7 (52.1 ± 20.6 N/m, 208.28%), but then progressively decreased until Day 21 (23.7 ± 3.2 N/m, 40.24%). In contrast, the biomechanical parameters of skin wound tissue measured by the material testing system showed a marked reduction upon wounding, and then gradually increased with time (all p<0.05). On Day 21, the ultimate tensile strength and stress of the skin wound tissue was about 50% of that of the unwounded skin; whereas the stiffness of the tissue recovered at a faster rate, reaching 97% of the pre-wounding status by Day 21. Overall, the present thesis demonstrated that for people with diabetes, particularly for those with neuropathy or ulceration, the epidermal plantar skin became thinner and the plantar soft tissues stiffened. In addition, an increase in subepidermal oedema was demonstrated in people with diabetic neuropathy and ulceration, which may partly contribute to a reduction in epidermal thickness at the pulp of the big toe. All of these changes may subsequently lead to the breaking down of skin in the diabetic foot. This implies that diabetes-associated changes in the biomechanical properties of plantar skin, plantar soft tissues, and foot swelling are potential risk factors of foot ulceration in people with diabetes. Therefore, regular examinations of the sole of the foot of people with diabetes and the wearing of proper shoes should be reinforced in order to prevent foot complications. As for the stiffness of diabetic foot ulcer tissues, we demonstrated that the peri-ulcer area was stiffer than the ulcerated tissues in a diabetic foot with ulcers. This greater magnitude of hardness and inelasticity in the peri-ulcer region may scatter some of the contractile forces for wound contraction during the healing process. The newly developed OCT-based air-jet indentation system is a reliable tool for characterizing the stiffness of soft tissues around the wound in a non-contact way in vivo. As for the changes in the biomechanical properties of skin wound tissues across different phases of the wound healing process, we found that stiffness recovered at a faster rate than tensile strength in rat skin wounds that were healing. Measurements made by the air-jet-indentation system and by the material testing systems involve different principles, but both systems can reflect the biomechanical properties of wound tissue.<br/><br/>Description: xxi, 609 p. : ill. (some col.) ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577P RS 2012 Chao http://hdl.handle.net/10397/5556 Title: Regulation in vascularity after extracorporeal shock wave therapy in individuals with proximal plantar fasciitis<br/><br/>Authors: Chen, Hongying<br/><br/>Abstract: Plantar fasciitis is one of the most common causes of heel pain, but its etiology and pathogenesis are unclear. Vascular disturbance with consequent metabolic impairment is thought to play an important role. Vascular changes have been observed in patients with plantar fasciitis and modulation in vascularity is detected in individuals with tendinopathy after extracorporeal shock wave therapy (ESWT). ESWT has been approved by the Food and Drug Administration (FDA) of the Unites States in 2000 for treating patients with plantar fasciitis and gives evident pain reduction when the treatment was delivered at low to medium intensity at weekly basis for multi-sessions. If treatment should be prescribed based on the stage of the disease, vascularization could be one of the determining factors in delineating a treatment protocol. In order to have a better understanding of the treatment’s efficacy, biological effects studies need to be assessed in the short and long term after treatment. Such information would enhance our understanding of the ESWT-induced biological changes in vascularization and form a scientific basis for ESWT’s clinical application. This project consisted of 5 inter-related studies. The first study (Chapter 2) aimed to establish a reliable measure to quantify the vascularity of the plantar fascia as well as delineate the minimum detectable changes and cut-off point for identifying individuals with and without unusual vascularization. Study 2 (Chapter 3) explored vascularization and fascia thickness in patients diagnosed with plantar fasciitis and able-bodied controls. The study also explored relationships between the duration of the disorder with vascularity and fascia thickness. In study 3 (Chapter 4), regulation in vascularity was assessed in patients with plantar fasciitis after 3 or 6 sessions of ESWT and compared with patients with no intervention. The influence of pre-intervention vascularization on treatment planning was explored in study 4 (Chapter 5). Patients with duration of symptoms less than 12 months were followed up 3 and 6 months after the application of ESWT. Factors affecting treatment success were investigated and reported in study 5(Chapter 6). Aside from vascularization and fascia thickness, the outcome measures included self-perceived pain and foot function.; Based on Power Doppler Ultrasonography, a quantitative vascularity index (VI) was defined which correlated well with Newman's grading scale. It provided a minimum detectable difference of 0.68% in vascularity. In addition, vascular index of 2.60% was shown to differentiate patients with and without morderate to severe vascularization. Vascularization and thickened plantar fascia were evident in the patient group. In patients with symptoms lasting less than 12 months, vascularity index was shown to be positively correlated with pain and foot function. Minimal vascularity was observed in subjects with symptoms lasting beyond 12 months. The plantar fascia in these patients had similar thickness as those with symptoms less than 12 months. Immediate after ESWT, regulation in vascularity was observed in 60% of the patients studied. The direction of change was shown to depend on the treatment dosage and baseline vascularization. Down-regulation in vascularity was observed in vascularized patients (with VI >2.6%) after 6 sessions of ESWT. Vascularity was up-regulated in non-vascularized patients after receiving either 3 or 6 sessions of ESWT. A VI score >1.55% at baseline was a strong predictor of unsuccessful recovery with only 3 sessions of ESWT, but 62.50% of patients with a baseline VI score <3.25% recovered successfully after 6 sessions of ESWT. No patients could be treated successfully if their pre-intervention VIs were beyond 3.25%. Regression of vascularity was continued to 6 months post intervention, and 91.67% patients with excellent treatment results had normal vascularity. Fascia thinning was evident after 3 months, and about 50% of the patients had regained normal fascia thickness by 6 months post intervention. Our findings thus indicate that 6 sessions of treatment were more effective for patients with greater vascularization. The above findings lead to 3 main conclusions. 1) Patients with plantar fasciitis for more than 3 months (9.21+ 6.44 months) show increased vascularity in the affected fascia. ESWT can modify the vascularity in 60% of patients, but the direction of regulation depends on the baseline vascularization and the number of treatment sessions. 2) Individuals with increased vascularization could not reach a satisfactory result after only 3 sessions of ESWT; 6 sessions of ESWT could improve about 60% of vascularized patients at 1 month follow-up. 3) The regression of vascularity after ESWT continues to 6 months post-intervention. This could be related to natural history as well as treatment effects from the shock wave. Regression analysis indicated that patients' baseline vascularization together with treatment protocol are two factors that affect treatment effectiveness in terms of pain reduction.<br/><br/>Description: xxiv, 226 leaves : ill. (some col.) ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577P RS 2012 Chen