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Standing up shifts blood to dependent parts of the body, and blood vessels in the leg become filled. The orthostatic blood volume accumulation in the small vessels is relatively unknown, although these may contribute significantly. We hypothesized that in healthy humans exposed to the upright posture, volume accumulation in small blood vessels contributes significantly to the total fluid volume accumulated in the legs. Considering that near-infrared spectroscopy (NIRS) tracks postural blood volume changes within the small blood vessels of the lower leg, we evaluated the NIRS-determined changes in oxygenated (Δ[O(2)Hb]), deoxygenated (Δ[HHb]) and total haemoglobin tissue concentration (Δ[tHb]) and in total leg volume by strain-gauge plethysmography during 70 deg head-up tilt (HUT; n = 7). In a second experiment, spatial and temporal reproducibility were evaluated with three NIRS probes applied on two separate days (n = 8). In response to HUT, an initially fast increase in [O(2)Hb] was followed by a gradual decline, while [HHb] increased continuously. The increase in [tHb] during HUT was closely related to the increase in total leg volume (r(2) = 0.95 ± 0.03). After tilt back, [O(2)Hb] declined below and [HHb] remained above baseline, whereas all NIRS signals gradually returned to baseline. Spatial heterogeneity was observed, and for two probes [tHb] was highly correlated between days (r(2) = 0.92 ± 0.09 and 0.91 ± 0.12), but less for the third probe (r(2) = 0.44 ± 0.36). The results suggest a non-linear accumulation of blood volume in the small vessels of the leg, with an initial fast phase followed by a more gradual increase at least partly contributing to the relocation of fluid during orthostatic stress.

Background: The unipodal stance task is a clinical task that quantifies postural stability and alignment of the lower limb joints, while weight bearing on one leg. As persons with knee osteoarthritis (KOA) have poor postural and knee joint stability, objective assessment of this task might be useful. Objective: To investigate the discriminant validity of three-dimensional joint kinematics and centre of mass displacement (COM) between healthy controls and persons with knee KOA, during unipodal stance using inertial sensors. Additionally, the reliability, agreement and construct validity are assessed to determine the reproducibility and accuracy of the discriminating parameters. Methods: Twenty healthy controls and 19 persons with unilateral severe KOA were included. Five repetitions of the unipodal stance task were simultaneously recorded by an inertial sensor system and a camera-based system (gold standard). Statistical significant differences in kinematic waveforms between healthy controls and persons with severe knee KOA were determined using one-dimensional statistical parametric mapping (SPM1D). Results: Persons with severe knee KOA had more lateral trunk lean towards the contralateral leg, more hip flexion throughout the performance of the unipodal stance task, more pelvic obliquity and COM displacement towards the contralateral side. However, for the latter two parameters the minimum detectable change was greater than the difference between healthy controls and persons with severe knee KOA. The construct validity was good (coefficient of multiple correlation 0.75, 0.83 respectively) and the root mean squared error (RMSE) was low (RMSE <1.5°) for the discriminant parameters. Conclusion: Inertial sensor based movement analysis can discriminate between healthy controls and persons with severe knee KOA for lateral trunk lean and hip flexion, but unfortunately not for the knee angles. Further research is required to improve the reproducibility and accuracy of the inertial sensor measurements before they can be used to assess differences in tasks with a small range of motion. [ABSTRACT FROM AUTHOR]

To analyze the impact of balance, lower-limb explosive strength and anthropometric variables on the result of the hop test in young elite female basketball athletes. Ninety young elite female basketball athletes (13–17 years), without current or recent lower-limb injury, were assessed in the off-season period of July 2021. Single leg hop test, countermovement jump, Y balance test and anthropometric outcomes were assessed. A correlation study and a regression model were performed to investigate the influence of such outcomes and the value of their participation on the hop test results. It was found a low-to-moderate correlation effect size for both countermovement jump (distance and power flight) and Y balance test values (except interlimb outcomes) with the single leg hop test results. Anthropometric outcomes did not show significant correlation (p > 0.05). Regression model revealed that for right hop test, countermovement jump values exhibited an adjusted determination coefficient of 0.408, (β = 0.249, p = 0.013), For left hop test, again the countermovement jump values (β = 0.229, p = 0.025), and left Y balance test values (β = 0.331, p = 0.011) jointly obtained an adjusted determination coefficient of 0.263 significant predictive value for countermovement jump outcomes in both right (β = 0.249, p = 0.013; β = 0.301; p = 0.031) and left leg (β = 0.229, p = 0.025; β = 0.365, p = 0.040), as well as certain Y balance outcomes values. Explosive strength, and dynamic balance although to a lesser extent, appear to be the most relevant physical-functional factors influencing the single leg hop test results among young elite female basketball athletes. These findings may a serve as a basis to implement targeted interventions, such as plyometric and balance training, for an enhancement on functional rehabilitation and reducing the risk of injury related to the hop test results. [ABSTRACT FROM AUTHOR]

In rheumatoid arthritis, the joints of the lower extremities are almost always affected. This is most conspicuous in the knee joint. In rheumatics, inflammatory osteoarthritis manifests itself comparably earlier than in patients with osteoarthritis. The focus of attention was primarily on the synovia with its destruction process and secondary changes. Now, driven by experimental research, dendritic cells and fibroblasts and molecular features are moving into the clinician's field of vision. Even in joints that appear to be in remission with no swelling or pain, the activity of these cells leads to changes in the capsule-ligaments. The complex deformities and instabilities caused by this, in conjunction with atrophy of the inter-articular musculature, have an impact on the activities of daily life (ADL). If these biomechanical aspects of the knee joint are not taken into account early on in therapy, the frequency of primary and secondary surgical treatment increases. The timely recognition of biomechanical pathologies and consistent treatment can contribute to improving the patient situation in addition to adequate medication therapy. [ABSTRACT FROM AUTHOR]

The estimation of the body's center of mass (CoM) trajectory is typically obtained using force platforms, or optoelectronic systems (OS), bounding the assessment inside a laboratory setting. The use of magneto-inertial measurement units (MIMUs) allows for more ecological evaluations, and previous studies proposed methods based on either a single sensor or a sensors' network. In this study, we compared the accuracy of two methods based on MIMUs. Body CoM was estimated during six postural tasks performed by 15 healthy subjects, using data collected by a single sensor on the pelvis (Strapdown Integration Method, SDI), and seven sensors on the pelvis and lower limbs (Biomechanical Model, BM). The accuracy of the two methods was compared in terms of RMSE and estimation of posturographic parameters, using an OS as reference. The RMSE of the SDI was lower in tasks with little or no oscillations, while the BM outperformed in tasks with greater CoM displacement. Moreover, higher correlation coefficients were obtained between the posturographic parameters obtained with the BM and the OS. Our findings showed that the estimation of CoM displacement based on MIMU was reasonably accurate, and the use of the inertial sensors network methods should be preferred to estimate the kinematic parameters. [ABSTRACT FROM AUTHOR]