RESUMO
PURPOSE: To investigate whether quantitative T2-times depend on lumbar intervertebral disc (IVD) level. METHODS: The lumbar spine (Th12/L1-L5/S1) of 101 participants (53.5% female, 30.0[± 3.6]years, 173.5[± 9.6]cm and 69.9[± 13.4]kg), without history of back pain, was examined on a 3T scanner with sagittal T2-mapping. All IVDs were stratified according to Pfirrmann grade and lumbar level, with mean T2-time determined for the entire IVD volume and in five subregions of interests. RESULTS: Significant level-dependent T2-time differences were detected, both for the entire IVD volume and its subregions. For the entire IVD volume, Pfirrmann grade 2 IVDs displayed 9-18% higher T2-times in Th12/L1 IVDs compared to L2/L3-L5/S1 IVDs (0.001 > p < 0.004) and significantly different T2-times in L1/L2-L2/L3 IVDs compared to most of the IVDs in the lower lumbar spine. In Pfirrmann grades 1, 3 and 4 IVDs, no significant level-dependent T2-time differences were observed for the entire IVD. More pronounced results were observed when comparing IVD subregions, with significant level-dependent differences also within Pfirrmann grade 1 and grade 3 IVDs. For example, in posterior IVD subregions mean T2-time was 80-82% higher in Th12/L1 compared to L3/L4-L4/L5 Pfirrmann grade 1 IVDs (p < 0.05) and 10-14% higher in L5/S1 compared to L3/L4-L4/L5 Pfirrmann grade 3 IVDs (0.02 > p < 0.001). DISCUSSION: Significant level-dependent T2-time differences within several Pfirrmann grades, both for the entire IVD volume and for multiple IVD subregions, were shown in this large cohort study. The T2-time differences between levels existed in both non-degenerated and degenerated IVDs. These findings show the importance of stratifying for lumbar level when quantitative IVD studies are performed using T2-mapping. These slides can be retrieved under Electronic Supplementary Material.
Assuntos
Disco Intervertebral/diagnóstico por imagem , Vértebras Lombares/diagnóstico por imagem , Imageamento por Ressonância Magnética , Adulto , Feminino , Humanos , MasculinoRESUMO
OBJECTIVE: To investigate the effects of 4-months intensive aquatic resistance training on body composition and walking speed in post-menopausal women with mild knee osteoarthritis (OA), immediately after intervention and after 12-months follow-up. Additionally, influence of leisure time physical activity (LTPA) will be investigated. DESIGN: This randomised clinical trial assigned eighty-seven volunteer postmenopausal women into two study arms. The intervention group (n = 43) participated in 48 supervised intensive aquatic resistance training sessions over 4-months while the control group (n = 44) maintained normal physical activity. Eighty four participants continued into the 12-months' follow-up period. Body composition was measured with dual-energy X-ray absorptiometry (DXA). Walking speed over 2 km and the knee injury and osteoarthritis outcome score (KOOS) were measured. LTPA was recorded with self-reported diaries. RESULTS: After the 4-month intervention there was a significant decrease (P = 0.002) in fat mass (mean change: -1.17 kg; 95% CI: -2.00 to -0.43) and increase (P = 0.002) in walking speed (0.052 m/s; 95% CI: 0.018 to 0.086) in favour of the intervention group. Body composition returned to baseline after 12-months. In contrast, increased walking speed was maintained (0.046 m/s; 95% CI 0.006 to 0.086, P = 0.032). No change was seen in lean mass or KOOS. Daily LTPA over the 16-months had a significant effect (P = 0.007) on fat mass loss (f2 = 0.05) but no effect on walking speed. CONCLUSIONS: Our findings show that high intensity aquatic resistance training decreases fat mass and improves walking speed in post-menopausal women with mild knee OA. Only improvements in walking speed were maintained at 12-months follow-up. Higher levels of LTPA were associated with fat mass loss. TRIAL REGISTRATION NUMBER: ISRCTN65346593.
Assuntos
Hidroterapia/métodos , Osteoartrite do Joelho/terapia , Treinamento Resistido/métodos , Velocidade de Caminhada/fisiologia , Idoso , Composição Corporal/fisiologia , Feminino , Seguimentos , Humanos , Pessoa de Meia-Idade , Osteoartrite do Joelho/fisiopatologia , Cooperação do Paciente , Esforço Físico/fisiologia , Pós-Menopausa/fisiologiaRESUMO
It is uncertain whether subjects with mild knee osteoarthritis, and who may be at risk of osteoporosis, can exercise safely with the aim of improving hip bone strength. This RCT showed that participating in a high-impact exercise program improved femoral neck strength without any detrimental effects on knee cartilage composition. INTRODUCTION: No previous studies have examined whether high-impact exercise can improve bone strength and articular cartilage quality in subjects with mild knee osteoarthritis. In this 12-month RCT, we assessed the effects of progressive high-impact exercise on femoral neck structural strength and biochemical composition of knee cartilage in postmenopausal women. METHODS: Eighty postmenopausal women with mild knee radiographic osteoarthritis were randomly assigned into the exercise (n = 40) or control (n = 40) group. Femoral neck structural strength was assessed with dual-energy X-ray absorptiometry. The knee cartilage region exposed to exercise loading was measured by the quantitative MRI techniques of T2 mapping and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC). Also, an accelerometer-based body movement monitor was used to evaluate the total physical activity loading on the changes of femoral neck strength in all participants. Training effects on the outcome variables were estimated by the bootstrap analysis of covariance. RESULTS: A significant between-group difference in femoral neck bending strength in favor of the trainees was observed after the 12-month intervention (4.4%, p < 0.01). The change in femoral neck bending strength remained significant after adjusting for baseline value, age, height, and body mass (4.0%, p = 0.020). In all participants, the change in bending strength was associated with the total physical activity loading (r = 0.29, p = 0.012). The exercise participation had no effect on knee cartilage composition. CONCLUSION: The high-impact training increased femoral neck strength without having any harmful effect on knee cartilage in women with mild knee osteoarthritis. These findings imply that progressive high-impact exercise is a feasible method in seeking to prevent hip fractures in postmenopausal women whose articular cartilage may also be frail.
Assuntos
Terapia por Exercício/métodos , Colo do Fêmur/fisiopatologia , Osteoartrite do Joelho/reabilitação , Osteoporose Pós-Menopausa/prevenção & controle , Absorciometria de Fóton , Cartilagem Articular/diagnóstico por imagem , Cartilagem Articular/fisiopatologia , Exercício Físico/fisiologia , Estudos de Viabilidade , Feminino , Fraturas do Quadril/etiologia , Fraturas do Quadril/prevenção & controle , Humanos , Articulação do Joelho/diagnóstico por imagem , Articulação do Joelho/fisiopatologia , Imageamento por Ressonância Magnética , Pessoa de Meia-Idade , Osteoartrite do Joelho/complicações , Osteoartrite do Joelho/fisiopatologia , Osteoporose Pós-Menopausa/etiologia , Fraturas por Osteoporose/etiologia , Fraturas por Osteoporose/prevenção & controle , Método Simples-CegoRESUMO
This review summarises current understanding of how bone is sculpted through adaptive processes, designed to meet the mechanical challenges it faces in everyday life and athletic pursuits, serving as an update for clinicians, researchers and physical therapists. Bone's ability to resist fracture under the large muscle and locomotory forces it experiences during movement and in falls or collisions is dependent on its established mechanical properties, determined by bone's complex and multidimensional material and structural organisation. At all levels, bone is highly adaptive to habitual loading, regulating its structure according to components of its loading regime and mechanical environment, inclusive of strain magnitude, rate, frequency, distribution and deformation mode. Indeed, the greatest forces habitually applied to bone arise from muscular contractions, and the past two decades have seen substantial advances in our understanding of how these forces shape bone throughout life. Herein, we also highlight the limitations of in vivo methods to assess and understand bone collagen, and bone mineral at the material or tissue level. The inability to easily measure or closely regulate applied strain in humans is identified, limiting the translation of animal studies to human populations, and our exploration of how components of mechanical loading regimes influence mechanoadaptation.
Assuntos
Osso e Ossos/fisiologia , Fenômenos Fisiológicos Musculoesqueléticos , Animais , HumanosRESUMO
OBJECTIVE: To study the efficacy of aquatic resistance training on biochemical composition of tibiofemoral cartilage in postmenopausal women with mild knee osteoarthritis (OA). DESIGN: Eighty seven volunteer postmenopausal women, aged 60-68 years, with mild knee OA (Kellgren-Lawrence grades I/II and knee pain) were recruited and randomly assigned to an intervention (n = 43) and control (n = 44) group. The intervention group participated in 48 supervised aquatic resistance training sessions over 16 weeks while the control group maintained usual level of physical activity. The biochemical composition of the medial and lateral tibiofemoral cartilage was estimated using single-slice transverse relaxation time (T2) mapping and delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC index). Secondary outcomes were cardiorespiratory fitness, isometric knee extension and flexion force and knee injury and OA outcome (KOOS) questionnaire. RESULTS: After 4-months aquatic training, there was a significant decrease in both T2 -1.2 ms (95% confidence interval (CI): -2.3 to -0.1, P = 0.021) and dGEMRIC index -23 ms (-43 to -3, P = 0.016) in the training group compared to controls in the full thickness posterior region of interest (ROI) of the medial femoral cartilage. Cardiorespiratory fitness significantly improved in the intervention group by 9.8% (P = 0.010). CONCLUSIONS: Our results suggest that, in postmenopausal women with mild knee OA, the integrity of the collagen-interstitial water environment (T2) of the tibiofemoral cartilage may be responsive to low shear and compressive forces during aquatic resistance training. More research is required to understand the exact nature of acute responses in dGEMRIC index to this type of loading. Further, aquatic resistance training improves cardiorespiratory fitness. TRIAL REGISTRATION NUMBER: ISRCTN65346593.
Assuntos
Pós-Menopausa , Cartilagem Articular , Feminino , Humanos , Articulação do Joelho , Imageamento por Ressonância Magnética , Osteoartrite do Joelho , Treinamento ResistidoRESUMO
OBJECTIVES: To investigate whether neuromuscular performance predicts lower limb bone strength in different lower limb sites in postmenopausal women with mild knee osteoarthritis (OA). METHODS: Neuromuscular performance of 139 volunteer women aged 50-68 with mild knee OA was measured using maximal counter movement jump test, isometric knee flexion and extension force and figure-of-eight-running test. Femoral neck section modulus (Z, mm(3)) was determined by data obtained from dual-energy X-ray absorptiometry. Data obtained using peripheral quantitative computed tomography was used to asses distal tibia compressive (BSId, g(2)/cm(4)) and tibial mid-shaft bending (SSImax(mid), mm(3)) strength indices. RESULTS: After adjustment for height, weight and age, counter movement jump peak power production was the strongest independent predictor for Z (ß=0.44; p<0.001) and for BSId (ß=0.32; p=0.003). This was also true in concentric net impulse for Z (ß=0.37; p=0.001) and for BSId (ß=0.40; p<0.001). Additionally, knee extension force (ß=0.30; p<0.001) and figure-of-eight-running test (ß= -0.32; p<0.001) were among strongest independent predictors for BSId after adjustments. For SSImax(mid), concentric net impulse (ß=0.33; p=0.002) remained as the strongest independent predictor after adjustments. CONCLUSIONS: Neuromuscular performance in postmenopausal women with mild knee OA predicted lower limb bone strength in every measured skeletal site.
Assuntos
Osteoartrite do Joelho/fisiopatologia , Desempenho Psicomotor/fisiologia , Tíbia/diagnóstico por imagem , Absorciometria de Fóton , Idoso , Força Compressiva , Feminino , Humanos , Pessoa de Meia-Idade , Pós-Menopausa , Tomografia Computadorizada por Raios XRESUMO
While it is widely acknowledged that bones adapt to the site-specific prevalent loading environment, reasonable ways to estimate skeletal loads are not necessarily available. For long bone shafts, muscles acting to bend the bone may provide a more appropriate surrogate of the loading than muscles expected to cause compressive loads. Thus, the aim of this study was to investigate whether mid-thigh muscle cross-sectional area (CSA) was a better predictor of tibial mid-shaft bone strength than mid-tibia muscle CSA in middle aged and older men. 181 Caucasian men aged 50-79 years (mean±SD; 61±7 years) participated in this study. Mid-femoral and mid-tibial bone traits cortical area, density weighted polar moment of area and muscle CSA [cm(2)] were assessed with computed tomography. Tibial bone traits were positively associated with both the mid-femur (r=0.44 to 0.46, P<0.001) and the mid-tibia muscle CSA (r=0.35 to 0.37, P<0.001). Multivariate regression analysis, adjusting for age, weight, physical activity and femoral length, indicated that mid-femur muscle CSA predicted tibial mid-shaft bone strength indices better than mid-tibia muscle CSA. In conclusion, the association between a given skeletal site and functionally adjacent muscles may provide a meaningful probe of the site-specific effect of loading on bone.
Assuntos
Fêmur/diagnóstico por imagem , Músculo Esquelético/diagnóstico por imagem , Tíbia/diagnóstico por imagem , Idoso , Fenômenos Biomecânicos , Fêmur/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/fisiologia , Tíbia/fisiologia , Tomografia Computadorizada por Raios XRESUMO
OBJECTIVE: Cortical porosity, particularly at the endocortical region, is recognised to play a central role in the pathogenesis of bone fragility. Therefore, the purpose of this study was to: 1) demonstrate how cortical volumetric BMD (vBMD) distribution can be analysed from (p)QCT images and 2) highlight the clinical significance of assessing regional density distribution of cortical bone. METHODS: We used pQCT to compare mid-tibial cortical volumetric BMD distribution of 20 young (age 24(SD2) years, mass 77(11) kg, height 178(6) cm) and 25 elderly (72(4) years, 75(9) kg, 172(5) cm) men. Radial and polar cortical vBMD distributions were analysed using a custom built open source analysis tool which allowed the cortex to be divided into three concentric cortical divisions and in 36 cortical sectors originating from the centroid of the bone. RESULTS: Mean vBMD did not differ between the groups (1135(16) vs. 1130(28) mg/cm, P = 0.696). In contrast, there was a significant age-group by radial division interaction for radial cortical vBMD (P<0.001). CONCLUSIONS: The proposed analysis method for analysing cortical bone density distribution of pQCT images was effective for detecting regional differences in cortical density between young and elderly men, which would have been missed by just looking at mean vBMD values.
Assuntos
Densidade Óssea/fisiologia , Calcificação Fisiológica/fisiologia , Processamento de Imagem Assistida por Computador/métodos , Adulto , Idoso , Bases de Dados Factuais , Humanos , Processamento de Imagem Assistida por Computador/normas , Masculino , Porosidade , Tomografia Computadorizada por Raios X/métodos , Tomografia Computadorizada por Raios X/normas , Adulto JovemRESUMO
UNLABELLED: The association of long-term sport-specific exercise loading with cross-sectional geometry of the weight-bearing tibia was evaluated among 204 female athletes representing five different exercise loadings and 50 referents. All exercises involving ground impacts (e.g., endurance running, ball games, jumping) were associated with thicker cortex at the distal and diaphyseal sites of the tibia and also with large diaphyseal cross-section, whereas the high-magnitude (powerlifting) and non-impact (swimming) exercises were not. INTRODUCTION: Bones adapt to the specific loading to which they are habitually subjected. In this cross-sectional study, the association of long-term sport-specific exercise loading with the geometry of the weight-bearing tibia was evaluated among premenopausal female athletes representing 11 different sports. METHODS: A total of 204 athletes were divided into five exercise loading groups, and the respective peripheral quantitative computed tomographic data were compared to data obtained from 50 physically active, non-athletic referents. Analysis of covariance was used to estimate the between-group differences. RESULTS: At the distal tibia, the high-impact, odd-impact, and repetitive low-impact exercise loading groups had approximately 30% to 50% (p < 0.05) greater cortical area (CoA) than the referents. At the tibial shaft, these three impact groups had approximately 15% to 20% (p < 0.05) greater total area (ToA) and approximately 15% to 30% (p < 0.05) greater CoA. By contrast, both the high-magnitude and repetitive non-impact groups had similar ToA and CoA values to the reference group at both tibial sites. CONCLUSIONS: High-impact, odd-impact, and repetitive low-impact exercise loadings were associated with thicker cortex at the distal tibia. At the tibial shaft, impact loading was not only associated with thicker cortex, but also a larger cross-sectional area. High-magnitude exercise loading did not show such associations at either site but was comparable to repetitive non-impact loading and reference data. Collectively, the relevance of high strain rate together with moderate-to-high strain magnitude as major determinants of osteogenic loading of the weight-bearing tibia is implicated.
Assuntos
Esportes/fisiologia , Tíbia/anatomia & histologia , Adolescente , Adulto , Antropometria/métodos , Densidade Óssea/fisiologia , Diáfises/anatomia & histologia , Diáfises/fisiologia , Feminino , Humanos , Músculo Esquelético/fisiologia , Tíbia/diagnóstico por imagem , Tíbia/fisiologia , Tomografia Computadorizada por Raios X , Suporte de Carga/fisiologia , Adulto JovemRESUMO
Bones adapt to prevalent loading, which comprises mainly forces caused by muscle contractions. Therefore, we hypothesized that similar associations would be observed between neuromuscular performance and rigidity of bones located in the same body segment. These associations were assessed among 221 premenopausal women representing athletes in high-impact, odd-impact, high-magnitude, repetitive low-impact, and repetitive nonimpact sports and physically active referents aged 17-40 years. The whole group mean age and body mass were 23 (5) and 63 (9) kg, respectively. Bone cross sections at the tibial and fibular mid-diaphysis were assessed with peripheral quantitative computed tomography (pQCT). Density-weighted polar section modulus (SSI) and minimal and maximal cross-sectional moments of inertia (Imin, Imax) were analyzed. Bone morphology was described as the Imax/Imin ratio. Neuromuscular performance was assessed by maximal power during countermovement jump (CMJ). Tibial SSI was 31% higher in the high-impact, 19% in the odd-impact, and 30% in the repetitive low-impact groups compared with the reference group (P < 0.005). Only the high-impact group differed from the referents in fibular SSI (17%, P < 0.005). Tibial morphology differed between groups (P = 0.001), but fibular morphology did not (P = 0.247). The bone-by-group interaction was highly significant (P < 0.001). After controlling for height, weight, and age, the CMJ peak power correlated moderately with tibial SSI (r = 0.31, P < 0.001) but not with fibular SSI (r = 0.069, P = 0.313). In conclusion, observed differences in the association between neuromuscular performance and tibial and fibular traits suggest that the tibia and fibula experience different loading environments despite their anatomical vicinity.
Assuntos
Atletas , Fíbula/diagnóstico por imagem , Tíbia/diagnóstico por imagem , Adolescente , Adulto , Densidade Óssea/fisiologia , Diáfises/anatomia & histologia , Diáfises/diagnóstico por imagem , Exercício Físico/fisiologia , Feminino , Fíbula/anatomia & histologia , Humanos , Tíbia/anatomia & histologia , Tomografia Computadorizada por Raios X , Adulto JovemRESUMO
The osteogenicity of a given exercise may be estimated by calculating an osteogenic index (OI) consisting of magnitude and rate of strain. Volleyball involves repetitive jumping and requires high power output and thus may be expected to be beneficial to bone and performance. The purpose of the present study was to examine if habitual volleyball playing is reflected in OI. Ten elderly habitual volleyball players [age 69.9 (SD 4.4) years] and ten matched controls volunteered [age 69.7 (4.2) years] as subjects. Distal tibia (d), tibial mid-shaft (50) and femoral neck (FN) bone characteristics were measured using pQCT and DXA. To estimate skeletal rigidity, cross-sectional area (ToA(50)), and compressive (BSI(d)) and bending strength indices (SSImax(50)) were calculated. Maximal performance was assessed with eccentric ankle plantar flexion, isometric leg press and countermovement jump (CMJ). A fast Fourier transform (FFT) was calculated from the acceleration of the center of mass during the CMJ. Maximal acceleration (MAG) and mean magnitude frequency (MMF) were selected to represent the constituents of OI. OI was calculated as the sum of the products of magnitudes and corresponding frequencies. Volleyball players had 7% larger ToA(50) and 37% higher power in CMJ, 15% higher MAG and 36% higher OI (P
Assuntos
Colo do Fêmur/anatomia & histologia , Osteogênese , Esforço Físico , Tíbia/anatomia & histologia , Voleibol , Absorciometria de Fóton , Aceleração , Adaptação Fisiológica , Fatores Etários , Idoso , Fenômenos Biomecânicos , Estudos de Casos e Controles , Colo do Fêmur/diagnóstico por imagem , Análise de Fourier , Humanos , Masculino , Tíbia/diagnóstico por imagem , Tomografia Computadorizada por Raios XRESUMO
BACKGROUND: Age-related cognitive decline may be delayed with appropriate interventions if those at high risk can be identified prior to clinical symptoms arising. Gait variability assessment has emerged as a promising candidate prognostic indicator, however, it remains unclear how sensitive gait variability is to early changes in cognitive abilities. RESEARCH QUESTION: Do community-dwelling adults over 65 years of age with subjective memory complaints differ from those with no subjective memory concerns in terms of laboratory-measured or free-living gait variability? METHODS: This cross-sectional study recruited 24 (age = 73.5(SD 6.4) years) community-dwelling people with subjective memory complaints and twenty seven (age = 70.9(4.3) years) individuals with no subjective memory concerns. A sample of 9 individuals with diagnosed mild dementia were also assessed (age = 86.5(7.0) years). Gait variability was assessed in a laboratory during walking at preferred pace (single-task) and while counting backward by seven (dual-task). Sixteen passes over a 4.88 m walkway in each condition were recorded and step length and duration variability was analysed. Free-living gait was assessed with a waist-worn accelerometer by identifying gait bouts of at least one min duration, and the mean multiscale sample entropy in one mins non-overlapping epochs is reported. Statistical inferences were based on analysis of variance using sex and group as the factors. RESULTS: No difference between those with subjective memory complaints and those without were observed in either laboratory- or free-living gait variability estimates. Both laboratory- and free-living gait variability were higher in those with mild dementia compared to the other groups. SIGNIFICANCE: Assuming that subjective memory complaints are on the pathway from cognitively intact to cognitively frail, the findings raise the hypothesis that subjective memory complaints occur earlier in the pathophysiology than measurable changes in laboratory or free living gait. Alternatively the gait variability assessments utilised may have been too insensitive.
Assuntos
Disfunção Cognitiva/fisiopatologia , Análise da Marcha , Marcha/fisiologia , Acelerometria , Idoso , Idoso de 80 Anos ou mais , Estudos Transversais , Demência , Entropia , Feminino , Humanos , Vida Independente , Masculino , MemóriaRESUMO
BACKGROUND: Wearable inertial sensors have been shown to provide valid mean gait characteristics assessments, however, assessment of variability is less convincingly established. RESEARCH QUESTION: What level of concurrent validity, and session-to-session reliability does an ankle-worn inertial measurement unit (IMU)-based gait assessment with a novel angular velocity-based gait event detection algorithm have among older adults? METHODS: Twenty seven (women Nâ¯=â¯17) participants volunteered (age 74.4 (SD 4.3) years, body mass 74.5 (12.0) kg, height 165.9 (9.9) cm). Right leg stance, swing, and stride duration and stride length, and stride velocity were concurrently assessed with motion capture and with an IMU from a 3â¯min self-paced walk up and back a 14â¯m track repeated twice a week apart. Gait variability was assessed as the SD of all of the registered strides. RESULTS: Significant difference was observed between methods for many of the mean stride characteristics and stride variability (all pâ¯<â¯0.05), fair to excellent agreement was observed for mean values of all of the five stride characteristics evaluated (intra-class correlation coefficient [ICC] from 0.43 to 1.00). However, poor agreement was observed for the SD of all of the evaluated stride characteristics (ICC from -0.25 to 0.00). Both methods indicated excellent session to session reliability for all of the five stride characteristics evaluated (ICC from 0.84 to 0.98, CV%RMS from 1.6% to 3.6%), whereas the variability characteristics exhibited poor to good reliability (ICC from 0.0 to 0.69, CV%RMS from 18.0% to 34.4%). SIGNIFICANCE: Excellent concurrent validity and reliability was observed for mean spatiotemporal stride characteristics, however, gait variability exhibited poor concurrent validity and reliability. Although IMUs and the presented algorithm could be used to assess mean spatiotemporal stride characteristics among older individuals, either a more reliable gait event detection algorithm or alternative analytical approaches should be used for gait variability.
Assuntos
Acelerometria/normas , Articulação do Tornozelo/fisiologia , Marcha/fisiologia , Caminhada/fisiologia , Acelerometria/instrumentação , Idoso , Algoritmos , Tornozelo , Feminino , Humanos , Masculino , Reprodutibilidade dos TestesRESUMO
Strains within the bone tissue play a major role in bone (re)modeling. These small strains can be assessed using experimental strain gage measurements, which are challenging and invasive. Further, the strain measurements are, in practise, limited to certain regions of superficial bones only, such as the anterior surface of the tibia. In this study, tibial strains occurring during walking were estimated using a numerical approach based on flexible multibody dynamics. In the introduced approach, a lower body musculoskeletal model was developed by employing motion capture data obtained from walking at a constant velocity. The motion capture data were used in inverse dynamics simulation to teach the muscles in the model to replicate the motion in forward dynamics simulation. The maximum and minimum tibial principal strains predicted by the model were 490 and -588 microstrain, respectively, which are in line with literature values from in vivo measurements. In conclusion, the non-invasive flexible multibody simulation approach may be used as a surrogate for experimental bone strain measurements and thus be of use in detailed strain estimations of bones in different applications.
Assuntos
Tíbia/fisiologia , Caminhada/fisiologia , Adulto , Fenômenos Biomecânicos , Simulação por Computador , Humanos , Imageamento Tridimensional , Masculino , Modelos Anatômicos , Estresse Mecânico , Suporte de Carga/fisiologiaRESUMO
Muscle mass and strength have been shown to be important factors in bone strength. Low muscular force predisposes to falling especially among elderly. Regular exercise helps to prevent falls and resulting bone fractures. Better understanding of muscle function and its importance on bone properties may thus add information to fracture prevention. Therefore the purpose of this study was to examine the relationship between bone strength and muscular force production. Twenty-young men [24 (2) years] and 20 [24 (3) years] women served as subjects. Bone compressive (BSI(d)) and bending strength indices (50 Imax) were measured with peripheral quantitative computed tomography (pQCT) at tibial mid-shaft and at distal tibia. Ankle plantarflexor muscle volume (MV) was estimated from muscle thickness measured with ultrasonography. Neuromuscular performance was evaluated from the measurements of maximal ground reaction force (GRF) in bilateral jumping and of eccentric maximal voluntary ankle plantarflexor torque (MVC). Specific tension (ST) of the plantarflexors was calculated by dividing the MVC with the muscle volume. Activation level (AL) was measured with superimposed twitch method. Distal tibia BSI(d) and tibial mid-shaft 50 Imax correlated positively with GRF, MVC and MV in men (r = 0.45-0.67, P < 0.05). Tibial mid-shaft 50 Imax and neuromuscular performance variables were correlated in women (r = 0.46-0.59, P < 0.05), whereas no correlation was seen in distal tibia. In the regression analysis, MV and ST could explain 64% of the variance in tibial mid-shaft bone strength and 41% of the variation in distal tibia bone strength. The study emphasizes that tibial strength is related to maximal neuromuscular performance. In addition, tibial mid-shaft seems to be more dependent on the neuromuscular performance, than distal tibia. In young adults, the association between bone adaptation and neuromuscular performance seems to be moderate and also site and loading specific.
Assuntos
Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Esforço Físico/fisiologia , Tíbia/fisiologia , Adulto , Força Compressiva , Módulo de Elasticidade , Feminino , Humanos , Masculino , Radiografia , Estresse Mecânico , Tíbia/diagnóstico por imagemRESUMO
AIM: A single session of skill or strength training can modulate the primary motor cortex (M1), which manifests as increased corticospinal excitability (CSE) and decreased short-latency intra-cortical inhibition (SICI). We tested the hypothesis that both skill and strength training can propagate the neural mechanisms mediating cross-transfer and modulate the ipsilateral M1 (iM1). METHODS: Transcranial magnetic stimulation (TMS) measured baseline CSE and SICI in the contralateral motor cortex (cM1) and iM1. Participants completed 4 sets of unilateral training with their dominant arm, either visuomotor tracking, metronome-paced strength training (MPST), self-paced strength training (SPST) or control. Immediately post training, TMS was repeated in both M1s. RESULTS: Motor-evoked potentials (MEPs) increased and inhibition was reduced for skill and MPST training from baseline in both M1s. Self-paced strength training and control did not produce changes in CSE and SICI when compared to baseline in both M1s. After training, skill and MPST increased CSE and decreased SICI in cM1 compared to SPST and control. Skill and MPST training decreased SICI in iM1 compared to SPST and control post intervention; however, CSE in iM1 was not different across groups post training. CONCLUSION: Both skill training and MPST facilitated an increase in CSE and released SICI in iM1 and cM1 compared to baseline. Our results suggest that synchronizing to an auditory or a visual cue promotes neural adaptations within the iM1, which is thought to mediate cross transfer.
Assuntos
Potencial Evocado Motor/fisiologia , Aprendizagem/fisiologia , Córtex Motor/fisiologia , Destreza Motora/fisiologia , Treinamento Resistido/métodos , Adulto , Estimulação Elétrica , Eletromiografia , Feminino , Humanos , Contração Isométrica , Masculino , Amplitude de Movimento Articular/fisiologia , Estatísticas não Paramétricas , Estimulação Magnética Transcraniana , Adulto JovemRESUMO
AIM: Strength training of one limb results in a substantial increase in the strength of the untrained limb, however, it remains unknown what the corticospinal responses are following either eccentric or concentric strength training and how this relates to the cross-education of strength. The aim of this study was to determine if eccentric or concentric unilateral strength training differentially modulates corticospinal excitability, inhibition and the cross-transfer of strength. METHODS: Changes in contralateral (left limb) concentric strength, eccentric strength, motor-evoked potentials, short-interval intracortical inhibition and silent period durations were analyzed in groups of young adults who exercised the right wrist flexors with either eccentric (N=9) or concentric (N=9) contractions for 12 sessions over 4weeks. Control subjects (N=9) did not train. RESULTS: Following training, both groups exhibited a significant strength gain in the trained limb (concentric group increased concentric strength by 64% and eccentric group increased eccentric strength by 62%) and the extent of the cross-transfer of strength was 28% and 47% for the concentric and eccentric group, respectively, which was different between groups (P=0.031). Transcranial magnetic stimulation revealed that eccentric training reduced intracortical inhibition (37%), silent period duration (15-27%) and increased corticospinal excitability (51%) compared to concentric training for the untrained limb (P=0.033). There was no change in the control group. CONCLUSION: The results show that eccentric training uniquely modulates corticospinal excitability and inhibition of the untrained limb to a greater extent than concentric training. These findings suggest that unilateral eccentric contractions provide a greater stimulus in cross-education paradigms and should be an integral part of the rehabilitative process following unilateral injury to maximize the response.
Assuntos
Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Inibição Neural/fisiologia , Tratos Piramidais/fisiologia , Treinamento Resistido , Punho/fisiologia , Adulto , Eletromiografia , Potencial Evocado Motor , Feminino , Humanos , Masculino , Músculo Esquelético/anatomia & histologia , Tamanho do Órgão , Estimulação Magnética TranscranianaRESUMO
BACKGROUND: Running wheels are commonly used to stimulate physical activity of mice. To control the effects of physical activity on study results, it is important to measure the total activity (all movements) of both sedentary and running wheel stimulated mice. NEW METHOD: Because there was a lack of a validated system, we built a force-plate based system specifically for this purpose. The validity of the system and its variables (activity index, activity time and distance) were tested in calibration measurements and in situ by measuring the activity of eight mice both with and without running wheels. Four mice served as sedentary controls. Activity index adds changes in vertical reaction forces induced by moving mice. The system records simultaneously all the activity, thus the wheel running is not distinguished from other activity. RESULTS: There were very strong associations between measured activity variables and their true values (R(2)=1, p<0.01). The mean differences to true values were: activity index -9.7% (95% limits of agreement (LOA), -28.7 to 9.4%), activity time +0.9% (LOA, -1.3 to 3.0%) and distance +0.7% (LOA, -4.7 to 6.1%). The running wheels increased activity index 211 ± 40% (mean ± SE), activity time 39 ± 3% and activity intensity 94 ± 16%. Activity index (R(2)=0.982, p<0.01), activity time (R(2)=0.618, p<0.01) and intensity (R(2)=0.920, p<0.01) were positively associated with running distance. COMPARISON WITH EXISTING METHODS: To our knowledge, this is the first method properly validated for this purpose. CONCLUSIONS: The system is valid for the quantitation of total physical activity of mice housed in cages with or without running wheels.
Assuntos
Actigrafia/instrumentação , Actigrafia/métodos , Atividade Motora , Corrida , Animais , Calibragem , Desenho de Equipamento , Abrigo para Animais , Masculino , Camundongos Endogâmicos C57BL , Fatores de Tempo , VoliçãoRESUMO
It is currently unknown whether knee replacement-associated bone loss is modified by rehabilitation programs. Thus, a sample of 45 (18 men and 25 women) persons with unilateral knee replacement were recruited; age 66 years (sd 6), height 169 cm (sd 8), body mass 83 kg (sd 15), time since operation 10 months (sd 4) to explore the associations between maximal torque/power in knee extension/flexion and femoral mid-shaft bone traits (Cortical cross-sectional area (CoA, mm(2)), cortical volumetric bone mineral density (CoD, mg/mm(3)) and bone bending strength index (SSI, mm(3))). Bone traits were calculated from a single computed tomography slice from the femoral mid-shaft. Pain in the operated knee was assessed with the WOMAC questionnaire. Stepwise regression models were built for the operated leg bone traits, with knee extension and flexion torque and power, age, height, body mass, pain score and time since operation as independent variables. CoA was 2.3% (P=0.015), CoD 1.2% (P<0.001) and SSI 1.6% (P=0.235) lower in the operated compared to non-operated leg. The overall proportions of the variation explained by the regression models were 50%, 29% and 55% for CoA, CoD and SSI, respectively. Body mass explained 12% of Coa, 11% of CoD and 11% of SSI (P≤0.003). Maximal knee flexion torque explained 38% of Coa, 7% of CoD and 44% of SSI (p≤0.047). For CoD time since operation also became a significant predictor (11%, P=0.045). Knee flexion torque of the operated leg was positively associated with bone strength in the operated leg. Thus, successful rehabilitation may diminish bone loss in the operated leg.
Assuntos
Artroplastia do Joelho/métodos , Artroplastia do Joelho/reabilitação , Fêmur/diagnóstico por imagem , Articulação do Joelho/cirurgia , Idoso , Artroplastia do Joelho/efeitos adversos , Densidade Óssea , Feminino , Fêmur/metabolismo , Fêmur/fisiopatologia , Humanos , Articulação do Joelho/fisiopatologia , Masculino , Modelos Biológicos , Contração Muscular/fisiologia , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Medição da Dor , Dor Pós-Operatória/etiologia , Dor Pós-Operatória/fisiopatologia , Amplitude de Movimento Articular , Estresse Mecânico , Inquéritos e Questionários , Fatores de Tempo , Tomografia Computadorizada por Raios X , TorqueRESUMO
Video-based measures of spontaneous activity of rodents are of interest in studying, e.g. physiology. However, video-based tracking methods typically require light. The purpose of the present study was to develop a video based method for tracking movements of mice during a dark period. The method was applied in comparing the dark and light period activities of mice. Ten male mice were used in the present study. The activity of the animals was monitored simultaneously with video and ground reaction force (GRF) recordings during consecutive 12h periods of artificial light and dark. Texture based background subtraction method was used to track the mouse from the video recording, while the weighted mean of vertical GRFs measured from four rectangularly arranged strain gauges was used for the GRF based tracking. The association between distance calculated from video and from vertical GRF data was r=0.99 (p<0.001). No difference between methods was observed (difference 0 (95% limits of agreement -1.2-1.2)km) after adjusting the distances calculated with the GRF method with the least squares method fit. The mean distances moved by mice during artificial light period were 4.9 (SD 2.4) and 6.4 (2.8)km measured with the GRF and video methods, respectively. The corresponding values for the dark period were higher: 7.7 (4.0) (p=0.012) and 10.0 (4.3)km (p=0.007). In conclusion, the video based method appeared to be feasible in estimating the distance moved by a mouse during the dark period.