Sex-related differential item functioning of the Jenkins Sleep Scale: a cross-sectional study among 77 967 employees in the Finnish public sector.

OBJECTIVES: To investigate if the Jenkins Sleep Scale (JSS) demonstrates sex-related differential item functioning (DIF). DESIGN: Cross-sectional study. SETTING: Survey data from the Finnish Public Sector study (2015-2017). PARTICIPANTS: 77 967 employees in the Finnish public sector, with a mean age of 51.9 (SD 13.1) years and 82% women. OUTCOME MEASURES: Item response theory estimates: difficulty and discrimination parameters of the JSS and differences in these parameters between men and women. RESULTS: The mean JSS total score was 6.4 (4.8) points. For all four items of the JSS, the difficulty parameter demonstrated a slight shift towards underestimation of the severity of sleep difficulties. The discrimination ability of all four items was moderate to high. For the JSS composite score, overall discrimination ability was moderate (0.98, 95% CI 0.97 to 0.99). Mild uniform DIF (p<0.001) was seen: two items showed better discrimination ability among men and two others among women. CONCLUSIONS: The JSS showed overall good psychometric properties among this healthy population of employees in the Finnish public sector. The JSS was able to discriminate people with different severities of sleep disturbances. However, when using the JSS, the respondents might slightly underestimate the severity of these disturbances. While the JSS may produce slightly different results when answered by men and women, these sex-related differences are probably negligible when applied to clinical situations.

Toward Tailored Rehabilitation by Implementation of a Novel Musculoskeletal Finite Element Analysis Pipeline.

Tissue-level mechanics (e.g., stress and strain) are important factors governing tissue remodeling and development of knee osteoarthritis (KOA), and hence, the success of physical rehabilitation. To date, no clinically feasible analysis toolbox has been introduced and used to inform clinical decision making with subject-specific in-depth joint mechanics of different activities. Herein, we utilized a rapid state-of-the-art electromyography-assisted musculoskeletal finite element analysis toolbox with fibril-reinforced poro(visco)elastic cartilages and menisci to investigate knee mechanics in different activities. Tissue mechanical responses, believed to govern collagen damage, cell death, and fixed charge density loss of proteoglycans, were characterized within 15 patients with KOA while various daily activities and rehabilitation exercises were performed. Results showed more inter-participant variation in joint mechanics during rehabilitation exercises compared to daily activities. Accordingly, the devised workflow may be used for designing subject-specific rehabilitation protocols. Further, results showed the potential to tailor rehabilitation exercises, or assess capacity for daily activity modifications, to optimally load knee tissue, especially when mechanically-induced cartilage degeneration and adaptation are of interest.

Associations of Metabolic Syndrome and Its Components with the Risk of Incident Knee Osteoarthritis Leading to Hospitalization: A 32-Year Follow-up Study.

OBJECTIVES: To examine whether metabolic syndrome or its individual components predict the risk of incident knee osteoarthritis (OA) in a prospective cohort study during a 32-year follow-up period. DESIGN: The cohort consisted of 6274 participants of the Mini-Finland Health Survey, who were free from knee OA and insulin-treated diabetes at baseline. Information on the baseline characteristics, including metabolic syndrome components, hypertension, elevated fasting glucose, elevated triglycerides, reduced high-density lipoprotein, and central obesity were collected during a health examination. We drew information on the incidence of clinical knee OA from the national Care Register for Health Care. Of the participants, 459 developed incident knee OA. In our full model, age, gender, body mass index, history of physical workload, smoking history, knee complaint, and previous injury of the knee were entered as potential confounding factors. RESULTS: Having metabolic syndrome at baseline was not associated with an increased risk of incident knee OA. In the full model, the hazard ratio for incident knee OA for those with metabolic syndrome was 0.76 (95% confidence interval [0.56, 1.01]). The number of metabolic syndrome components or any individual component did not predict an increased risk of knee OA. Of the components, elevated plasma fasting glucose was associated with a reduced risk of incident knee OA (hazard ratio 0.71, 95% confidence interval [0.55, 0.91]). CONCLUSIONS: Our findings do not support the hypothesis that metabolic syndrome or its components increase the risk of incident knee OA. In fact, elevated fasting glucose levels seemed to predict a reduced risk.

Eight-year trajectories of changes in health-related quality of life in knee osteoarthritis: Data from the Osteoarthritis Initiative (OAI).

BACKGROUND: Knee osteoarthritis (OA) worsens health-related quality of life (HRQoL) but the symptom pathway varies from person to person. We aimed to identify groups of people with knee OA or at its increased risk whose HRQoL changed similarly. Our secondary aim was to evaluate if patient-related characteristics, incidence of knee replacement (KR) and prevalence of pain medication use differed between the identified HRQoL trajectory groups. METHODS: Eight-year follow-up data of 3053 persons with mild knee OA or at increased risk were obtained from the public Osteoarthritis Initiative (OAI) database. Group-based trajectory modeling was used to identify patterns of experiencing a decrease of ≥10 points (Minimal Important Change, MIC) in the Quality of Life subscale of the Knee injury and Osteoarthritis Outcome Score compared to baseline. Multinomial logistic regression, Cox regression and generalized estimating equation models were used to study secondary aims. RESULTS: Four HRQoL trajectory groups were identified. Persons in the 'no change' group (62.9%) experienced no worsening in HRQoL. 'Rapidly' (9.5%) and 'slowly' worsening (17.1%) groups displayed an increasing probability of experiencing the MIC in HRQoL. The fourth group (10.4%) had 'improving' HRQoL. Female gender, higher body mass index, smoking, knee pain, and lower income at baseline were associated with belonging to the 'rapidly worsening' group. People in 'rapidly' (hazard ratio (HR) 6.2, 95% confidence interval (CI) 3.6-10.7) and 'slowly' worsening (HR 3.4, 95% CI 2.0-5.9) groups had an increased risk of requiring knee replacement. Pain medication was more rarely used in the 'no change' than in the other groups. CONCLUSIONS: HRQoL worsening was associated with several risk factors; surgical and pharmacological interventions were more common in the poorer HRQoL trajectory groups indicating that HRQoL does reflect the need for OA treatment. These findings may have implications for targeting interventions to specific knee OA patient groups.

Health-related quality of life in relation to symptomatic and radiographic definitions of knee osteoarthritis: data from Osteoarthritis Initiative (OAI) 4-year follow-up study.

BACKGROUND: The purpose was to quantify the decrement in health utility (referred as disutility) associated with knee osteoarthritis (OA) and different symptomatic and radiographic uni- and bilateral definitions of knee OA in a repeated measures design of persons with knee OA or at increased risk of developing knee OA. METHODS: Data were obtained from the Osteoarthritis Initiative database. SF-12 health-related quality of life was converted into SF-6D utilities, and were then handled as the health utility loss by subtracting 1.000 from the utility score, yielding a negative value (disutility). Symptomatic OA was defined by radiographic findings (Kellgren-Lawrence, K-L, grade ≥ 2) and frequent knee pain in the same knee. Radiographic OA was defined by five different definitions (K-L ≥ 2 unilaterally / bilaterally, or the highest / mean / combination of K-L grades of both knees). Repeated measures generalized estimating equation (GEE) models were used to investigate disutility in relation to these different definitions. RESULTS: Utility decreased with worsening of symptomatic or radiographic status of knee OA. The participants with bilateral and unilateral symptomatic knee OA had 0.03 (p < 0.001) and 0.02 (p < 0.001) points lower utility scores, respectively, compared with the reference group. The radiographic K-L grade 4 defined as the mean or the highest grade of both knees was related to a decrease of 0.04 (p < 0.001) and 0.03 (p < 0.001) points in utility scores, respectively, compared to the reference group. CONCLUSIONS: Knee OA is associated with diminished health-related quality of life. Health utility can be quantified in relation to both symptomatic and radiographic uni- and bilateral definitions of knee OA, and these definitions are associated with differing disutilities. The performance of symptomatic definition was better, indicating that pain experience is an important factor in knee OA related quality of life.

Effectiveness of a cognitive-behavioural group intervention for knee osteoarthritis pain: a randomized controlled trial.

OBJECTIVE: To assess the effectiveness of a six week cognitive-behavioural group intervention in patients with knee osteoarthritis pain. DESIGN: Single-blinded randomized controlled trial. STUDY SETTING: Primary care providers in a medium-sized city in Finland. PATIENTS: A total of 111 participants aged from 35 to 75 with clinical symptoms and radiographic grading (Kellgren-Lawrence 2-4) of knee osteoarthritis were included. INTERVENTIONS: In the intervention group, 55 participants attended a cognitive-behavioural training programme for pain management with six weekly group sessions supervised by a psychologist and a physiotherapist. Concurrently, they and the 56 participants of the control group continued in ordinary GP care that was not altered by the study. MAIN MEASURES: The primary outcome on three-month and 12-month follow-up was the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis index pain subscale. Secondary outcome measures included self-reports of pain and physical function, health-related quality of life, and a comprehensive set of psychological questionnaires. RESULTS: Mixed model results showed no significant differences between the intervention and control group for any measures of pain or function. A significant difference between the groups was found in the Pain Self-Efficacy Questionnaire (Pr = 0.022) in favour of the control group, and in the RAND-36 emotional well-being subscale in favour of the intervention group (Pr = 0.038). Conventional group comparisons of mean follow-up values showed no significant differences in any of the outcome variables. CONCLUSION: This trial could not confirm the hypothesized advantage of a cognitive-behavioural training programme over ordinary GP care in knee osteoarthritis pain patients. TRIAL REGISTRATION: Current Controlled Trials ISRCTN64794760.

Short-term exercise-induced improvements in bone properties are for the most part not maintained during aging in hamsters.

Physical exercise during growth affects composition, structure and mechanical properties of bone. In this study we investigated whether the beneficial effects of exercise during the early growth phase have long-lasting effects or not. Female Syrian golden hamsters (total n=152) were used in this study. Half of the hamsters had access to running wheels during their rapid growth phase (from 1 to 3months of age). The hamsters were sacrificed at the ages of 1, 3, 12, and 15months. The diaphysis of the mineralized humerus was analyzed with microCT and subjected to three-point-bending mechanical testing. The trabecular bone in the tibial metaphysis was also analyzed with microCT. The collagen matrix of the humerus bone was studied by tensile testing after decalcification. The weight of the hamsters as well as the length of the bone and the volumetric bone mineral density (BMDvol) of the humerus was higher in the running group at the early age (3months). Moreover, the mineralized bone showed improved mechanical properties in humerus and had greater trabecular thickness in the subchondral bone of tibia in the runners. However, by the age of 12 and 15months, these differences were equalized with the sedentary group. The tensile strength and Young's modulus of decalcified humerus were higher in the runners at early stage, indicating a stronger collagen network. In tibial metaphysis, trabecular thickness was significantly higher for the runners in the old age groups (12 and 15months). Our study demonstrates that physical exercise during growth improves either directly or indirectly through weight gain bone properties of the hamsters. However, the beneficial effects were for the most part not maintained during aging.

Determinants of pain and functioning in hip osteoarthritis - a two-year prospective study.

OBJECTIVE: To identify predictors of pain and disability in hip osteoarthritis. DESIGN: A prospective analysis of determinants of pain and functioning in hip osteoarthritis. STUDY SETTING: Rehabilitation clinic in a central hospital. PATIENTS: A total of 118 men and women aged 55-80 years who had radiologically diagnosed hip osteoarthritis and associated clinical symptoms and participated in a randomized controlled trial. MAIN MEASURES: The self-reported disease-specific pain and physical function were assessed using the pain and functioning subscales of the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis index. The self-reported generic physical and mental functioning were assessed by using the Finnish-validated SF-36-item Health Survey RAND-36 subscales for function and physical and mental component summary scores. Outcome measures were recorded at 0, 3, 6, 12, 18 and 24 months. RESULTS: Multivariate linear mixed model analyses revealed that lower disease-specific pain score and better functioning (WOMAC) were predicted by higher educational level (9.61 (3.15 to 16.07); 9.07 (2.05 to 16.09)), supervised exercise training (-10.13 (-17.87 to -2.39); -11.58 (-19.40 to -3.77)), habitual conditioning physical activity (-0.48 (-0.96 to -0.01); -0.39 (-0.84 to 0.05)), absence of comorbidities (-6.30 (-12.35 to -0.24); -7.87 (-14.45 to -1.30)) and absence of additional knee osteoarthritis (-7.62 (-13.87 to -1.36); -8.02 (-14.81 to -1.23)), respectively. The same factors, except for the comorbidities, also predicted general physical functioning score (RAND-36). CONCLUSIONS: Higher education, absence of knee osteoarthritis and comorbidities, supervised exercise training and habitual conditioning physical activity predicted a lower presence of pain and better functional status in patients with hip osteoarthritis.

Minor influence of lifelong voluntary exercise on composition, structure, and incidence of osteoarthritis in tibial articular cartilage of mice compared with major effects caused by growth, maturation, and aging.

We investigated the effects of lifelong voluntary exercise on articular cartilage of mice. At the age of 4 weeks C57BL mice (n = 152) were divided into two groups, with one group serving as a sedentary control whereas the other was allowed free access to a running wheel from the age of 1 month onward. Mice were euthanized at four different time points (1, 2, 6, and 18 months of age). Articular cartilage samples were gathered from the load-bearing area of the tibial medial plateaus, and osteoarthritis was graded. Additionally, the proteoglycan content distribution was assessed using digital densitometry, collagen fibril orientation, and parallelism with polarized light microscopy, and collagen content using Fourier transform infrared imaging spectroscopy. The incidence of osteoarthritis increased with aging, but exercise had no effect on this trend. Furthermore, the structure and composition revealed significant growth, maturation, and age-dependent properties. Exercise exerted a minor effect on collagen fibril orientation in the superficial zone. Fibril orientation at 2 months of age was more perpendicular to surface (p < 0.05) in controls compared with runners, whereas the situation was reversed at the age of 18 months (p < 0.05). The collagen content of the superficial zone was higher (p < 0.01) at the age of 18 months in controls compared with runners but the proteoglycan content did not display any exercise-dependent changes. In conclusion, growth, maturation, and aging exerted a clear effect on integrity, structure, and composition of medial tibial plateau articular cartilage in mice, whereas lifelong voluntary exercise had only a minor effect on collagen architecture and content.

Economic evaluation of multidisciplinary rehabilitation after primary total knee arthroplasty based on a randomized controlled trial.

OBJECTIVE: To conduct an economic evaluation of a multidisciplinary, biopsychosocial outpatient rehabilitation program implemented 2-4 months after total knee arthroplasty (TKA), compared with conventional orthopedic care. METHODS: After surgery, 86 patients were randomized to a multidisciplinary rehabilitation group (n = 44) or a conventional orthopedic care group (n = 42). Alongside the randomized controlled trial, we estimated the costs of rehabilitation, health care resource use, and community support. Information about resource use was collected by means of a questionnaire together with data from hospital records. The primary outcome (effectiveness) measure was change in self-reported functional capacity and the secondary measure was quality-adjusted life years (QALYs) gained during the 12-month followup. Cost-effectiveness was assessed from between-group differences in costs, change in functional capacity, and QALYs gained. RESULTS: Both protocols of providing rehabilitation services turned out to be equally effective, but the conventional orthopedic care protocol was unequivocally cost saving: the saving was €1,830 per patient (95% confidence interval -548, 3,623) using the available direct cost data. CONCLUSION: Multidisciplinary rehabilitation for unselected osteoarthritis patients in the subacute period of recovery after TKA is not a cost-effective use of health care resources. Similar rehabilitation protocols cannot be recommended for clinical pathways of TKA in the future.

A pragmatic randomized controlled study of the effectiveness and cost consequences of exercise therapy in hip osteoarthritis.

OBJECTIVE: To evaluate the short- and long-term effectiveness of exercise training in relation to pain, function and direct costs to health care systems attributable to hip osteoarthritis. DESIGN: Prospective, two-year randomized controlled trial. SETTING: An outpatient primary health care setting. SUBJECTS: One hundred and twenty men and women aged from 55 to 80, with radiologically diagnosed hip osteoarthritis with associated clinical symptoms. INTERVENTIONS: The combined exercise and general practitioner (GP) care group received 12 supervised (once per week) exercise sessions at the baseline and four additional booster sessions one year later. Both groups received standard GP care. MAIN MEASURES: The WOMAC Osteoarthritis Index, physical functioning score of RAND-36 (SF-36), the use and health care system costs of doctor visits and physiotherapy associated with hip osteoarthritis, number of total hip replacements, the use of analgesic and non-steroidal anti-inflammatory drugs (NSAIDs), performance-based outcome scores and body mass index (BMI). RESULTS: There were no differences between the groups with respect to WOMAC hip pain, physical functioning score of RAND-36, performance-based outcome scores or BMI. The effect of the exercise intervention on WOMAC function was statistically significant at 6 months (mean = -7.5; 95% confidence interval (CI) -13.9 to -1.0; P = 0.02) and 18 months (mean = -7.9; 95% CI -15.3 to -0.4; P = 0.04). There were no statistically significant differences in the total health care system costs between the groups. CONCLUSION: The mostly home-based exercise training programme provided in this study did not result in reduced hip pain over the two-year follow-up period.

Sample size for prospective studies of hip joint space width narrowing in osteoarthritis by the use of radiographs.

OBJECTIVE: To determine the number of participants required in controlled clinical trials investigating the progression of osteoarthritis (OA) of the hip as evaluated by the joint space width (JSW) on radiographs and to evaluate the reproducibility of the JSW measurement methods. MATERIALS AND METHODS: Anteroposterior radiographs of hip were taken from 13 healthy volunteers and from 18 subjects with radiographic hip OA. The reproducibility of the JSW was determined from four segments using digital caliper measurements performed on film radiographs and using semiautomatic computerized image analysis of digitized images. Pearson correlation coefficient, coefficient of variability [CV (%)], and sample size values were calculated. RESULTS: It was found that 20 was a typical number of patients for a sufficiently powered study. The highest sample size was found in subjects with OA in the lateral segment. The reproducibility of the semiautomatic computerized method was not significantly better than the digital caliper method. CONCLUSION: The number of study subjects required to detect a significant joint space narrowing in follow-up studies is influenced by the baseline hip joint OA severity. The JSW measurements with computerized image analysis did not improve the reproducibility and thus performing JSW measurements with a digital caliper is acceptable.

[Myofascial pain syndrome--fascial muscle pain]. / Myofaskiaalinen kipuoireyhtymä--lihasjuostekipu.

Symptoms of myofascial pain syndrome, i.e. fascial muscle pain may occur in several areas of the body, particularly in the neck-shoulder region. The muscle pain symptom in the neck-shoulder region is commonly termed tension neck pain or nonspecific neck pain, but myofascial pain syndrome can also be distinguished into its own diagnosis. This review deals with the clinical picture of myofascial pain syndrome along with pathophysiological hypotheses and treatment options.

Postural control and thigh muscle activity in men with knee osteoarthritis.

The aim of this study was to examine the standing balance and the function of vastus medialis (VM) and biceps femoris (BF) muscles with surface electromyography (EMG). Fifty-four subjects with uni- or bilateral knee osteoarthritis (OA) (aged 50-69 years) and 53 age-matched randomly selected clinically and radiologically healthy men participated in this study. Postural control was assessed on a force platform with a bipedal stance with eyes open (EO) and closed (EC) and a monopedal stance with EO. The balance parameters, mean sway velocity, velocity along AP and ML axes, elliptical area, standard deviation of center of pressure, average radial displacement, mean frequency and frequency domain balance parameters and different power spectral density frequency bands were determined. Root mean square (RMS) for EMG amplitude, mean EMG frequency (f(EMG,mean)) and median EMG frequency (f(EMG,med)) of motor unit activity were calculated from the normalized EMG data. During bipedal stance with EC and EO, there were no significant differences in balance parameters between groups, but during bipedal stance with EO, the RMS in VM was about 56% higher (p<0.05) in subjects with knee OA than in the control subjects and the values of f(EMG,mean) and f(EMG,med) were about 48% higher (p<0.05) in control subjects than subjects with knee OA. It is concluded that subjects with knee OA do not have any standing balance deficit, but they do exhibit increased muscle activity in VM muscle compared to control subjects.

Collagen and mineral deposition in rabbit cortical bone during maturation and growth: effects on tissue properties.

We characterized the composition and mechanical properties of cortical bone during maturation and growth and in adult life in the rabbit. We hypothesized that the collagen network develops earlier than the mineralized matrix. Growth was monitored, and the rabbits were euthanized at birth (newborn), and at 1, 3, 6, 9, and 18 months of age. The collagen network was assessed biochemically (collagen content, enzymatic and non-enzymatic cross-links) in specimens from the mid-diaphysis of the tibia and femur and biomechanically (tensile testing) from decalcified whole tibia specimens. The mineralized matrix was analyzed using pQCT and 3-point bend tests from intact femur specimens. The collagen content and the Young's modulus of the collagen matrix increased significantly until the rabbits were 3 months old, and thereafter remained stable. The amount of HP and LP collagen cross-links increased continuously from newborn to 18 months of age, whereas PEN cross-links increased after 6 months of age. Bone mineral density and the Young's modulus of the mineralized bone increased until the rabbits were at least 6 months old. We concluded that substantial changes take place during the normal process of development in both the biochemical and biomechanical properties of rabbit cortical bone. In cortical bone, the collagen network reaches its mature composition and mechanical strength prior to the mineralized matrix.

Multidisciplinary rehabilitation after primary total knee arthroplasty: a randomized controlled study of its effects on functional capacity and quality of life.

OBJECTIVE: To examine whether a multidisciplinary rehabilitation programme can improve functional recovery and quality of life and reduce the use of rehabilitation services compared with conventional care one year after total knee arthroplasty. DESIGN: Prospective, randomized, non-blinded, controlled trial. SETTING: An outpatient centre-based setting. SUBJECTS: Eighty-six patients who were scheduled for primary total knee arthroplasty due to osteoarthritis of the knee. INTERVENTIONS: A ten-day multidisciplinary rehabilitation programme, which was focused on enhancing functional capacity, was organized 2-4 months after surgery. In both groups, a standard amount of physiotherapy was included in conventional care. MAIN MEASURES: The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the 15D, 15-m walk test, stair test, isometric strength measurement of the knee. Use of rehabilitation services was asked about with a questionnaire. Outcomes were assessed preoperatively and at 2-, 6- and 12-month follow-ups. RESULTS: In both groups, functional capacity and quality of life improved significantly. The mean absolute change in the WOMAC function score was -32.4 mm (SD 26.4) in the rehabilitation group and -32.8 mm (SD 20.1) in the control group (P-time*group = 0.40). No difference was found between groups in any outcome measure or in the use of rehabilitation services during the study period. CONCLUSIONS: This study indicates that for knee osteoarthritis patients treated with primary total knee arthroplasty, a 10-day multidisciplinary outpatient rehabilitation programme 2-4 months after surgery does not yield faster attainment of functional recovery or improvement in quality of life than can be achieved with conventional care.

Obesity, physically demanding work and traumatic knee injury are major risk factors for knee osteoarthritis--a population-based study with a follow-up of 22 years.

OBJECTIVE: Several studies have shown that knee OA is associated with obesity, physical stress at work, traumatic knee injuries, heredity and female gender. However, the body of such evidence comes from cross-sectional or case-control studies, and from only a few follow-up studies, mostly of short duration. Based on the nationwide Mini-Finland Health Survey, we analysed the potential risk factors for prediction of incident knee OA in the long term. METHODS: Focused on major health problems, the survey was carried out in 1978-80 in a sample of 8000 subjects, representative of the Finnish population aged > or =30 years. Altogether 823 subjects free from knee OA at the baseline were re-examined in 2000-01, and after the intervening 22 years 94 new cases of knee OA were found. Knee OA was diagnosed on both occasions by physicians using information on disease histories, symptoms and standardized clinical examinations. RESULTS: The risk of developing knee OA was strongly associated with BMI (kg/m(2)); adjusted for age and gender and other covariates, and compared with the reference category (BMI < 25.0); the relative odds ratios (ORs) with 95% CIs were 1.7 (95% CI 1.0, 2.8) and 7.0 (95% CI 3.5, 14.10) for subjects with BMIs 25.0-29.9 and > or =30.0, respectively. Similarly, the adjusted OR for the heaviest category of physical stress at work was 18.3 (95% CI 4.2, 79.4) compared with the lightest category, and 5.1 (95% CI 1.4, 19.0) for permanent complaints due to past knee injury. CONCLUSIONS: This prospective study confirms the roles of obesity, heavy work load and knee injury in the aetiology of knee OA.

Myofascial syndrome and pain: A neurophysiological approach.

It has been debated whether muscle spindles have a role in myofascial pain or not. We present a number of arguments for the former hypothesis. It was hypothesized that firing of intrafusal muscle fibres, i.e. fusimotor activity can be observed as "end plate spikes" (EPSs) in electromyography (EMG). The EPSs may be found in local active spots of muscle, often associated with miniature end plate potentials (MEPPs). Insertion of EMG needle electrodes into an active spot is painful, indicating nociception in the muscle spindle. Myofascial syndrome patients have taut bands with active trigger points (TrPs) in painful muscles. End plate activity (EPSs and MEPPs) is a significantly more common finding in TrPs of myofascial pain than in control points of the muscle, indicating the presence of muscle spindles. However, some control sites may show EPSs of normal muscle spindles. Increased amount of inflammatory metabolites have been observed in active TrPs. Muscle spindle is a capsulated gel-filled container, where inflammatory and contraction metabolites may be heavily concentrated during sustained fusimotor activation. Thus the intrafusal chemosensitive pain mediating III- and IV-afferents are sensitized and activated. Intrafusal inflammation causes further reflex activation of the fusimotor and skeletofusimotor systems via sensitized III- and IV-afferents. The taut band itself may be a contracture (rigor) of local skeletofusimotor (beta) units caused by sustained reflex drive by the given muscle spindles. In EMG this may be seen as complex repetitive discharges. We conclude that TrPs of myofascial pain are related to painful muscle spindles in taut bands.

Long-term voluntary exercise of male mice induces more beneficial effects on cancellous and cortical bone than on the collagenous matrix.

The effects of lifelong physical exercise on the composition, structure and mechanical properties of bone are not well understood. Earlier, we found that voluntary physical exercise improved various properties of bone in maturing male mice up to 6 months of age. In this study, we extended the previous study to 18 months. Half of the mice (total N=144) had access to running wheels while half were kept sedentary. The collagen network was assessed biochemically and by tensile testing of decalcified bone. The mineralized femur was analyzed with pQCT and three-point-bending of the diaphysis and neck-strength-test. The proximal tibia was analyzed with microCT. The bone collagen revealed inferior tensional properties with aging and the mineralized femur demonstrated decreased stiffness with age. In the running mice, tensile properties and the BMD were reduced at 18 months of age compared to the sedentary mice. In contrast, the stiffness of both the diaphysis and femoral neck was higher, and trabecular architecture and structure were improved in the running mice. In summary, the results suggest that lifelong exercise training of male mice results in more beneficial effects on intact mineralized bone in both the diaphysis and epiphysis than on bone collagenous matrix.

Physical exercise improves properties of bone and its collagen network in growing and maturing mice.

This study characterized bone structure, composition, and mechanical properties in growing male mice. The development of the collagen network during maturation was monitored, and the effect of voluntary physical exercise was investigated. We hypothesized that increased bone loading from exercise would increase the amount and improve the properties of the collagen network during growth and maturation. Half of the mice (total n = 168) had access to running wheels, while half were kept sedentary. Weight and running activity were recorded, and groups of mice were killed at 1, 2, 4, and 6 months of age. The collagen network was assessed by biochemical evaluation of collagen content and cross-links and by tensile testing of decalcified bone. Mineralized femur was analyzed with pQCT and three-point-bending and femoral neck-strength tests. After 6 months, the exercising mice had 10% lower body weight than the sedentary group. There was no difference in the amount of collagen or collagen cross-links, while tensile testing had higher breaking force and stiffness of the collagen network in runners after 4 months but not after 6 months. The bone mineral density and cross-sectional area were higher in the running group after 6 months. Runners also showed higher breaking force and stiffness of the diaphysis and the femoral neck at 2 and 6 months. The significant modulation of mechanical properties of the collagen network without any change in collagen content indicates that physical exercise improves properties of the collagen network in maturing bone. The improvement after exercise of the properties of mineralized bone appears to be more pronounced and long-lasting compared to the early improved properties of the collagen network.