735 research outputs found
Balance Performance across the Lifespan Assessed by the Leonardo Mechanograph®: A Cross-Sectional Study
Reference values of sway parameters have not been published for the Leonardo mechanograph® so far. The aim of this cross-sectional study was to determine normative values on postural control measured by the force plate Leonardo Mechanograph® and to analyze the influence of age and sex on balance performance. A set of standardized standing positions with eyes opened (Romberg, semi-tandem, tandem, unipedal standing) was carried out. Analysis of covariance (ANCOVA) was used to detect age-and sex-related differences in center of pressure (COP) parameters (path length, velocity, elliptical area, anterior-posterior, and medio-lateral directions). Measurements were available for 570 subjects aged 20–86 years. Statistical analysis showed a high effect of age group on postural control (partial n² between 0.1 and 0.4) with a U-shaped dependency between postural control and age for all area- and path-related COP parameters, with the largest sway in the youngest (aged 20–40) and the oldest age group (aged 60–86). For velocity of COP, a linear deterioration with increasing age was found. Medio-lateral components of COP are likely to indicate the extent of postural control. Significant sex differences were not clearly supported by current findings. Age- and sex-related normative values are a useful resource for diagnostic, research, and training
Quantifying Changes in the Spatial Structure of Trabecular Bone
We apply recently introduced measures of complexity for the structural
quantfication of distal tibial bone. For the first time, we are able to
investigate the temporal structural alteration of trabecular bone. Based on
four patients, we show how bone may alter due to temporal immobilisation
Changes in lower extremity muscle function after 56 days of bed rest
Preservation of muscle function, known to decline in microgravity and simulation (bed rest), is important for successful spaceflight missions. Hence, there is great interest in developing interventions to prevent musclefunction
loss. In this study, 20 males underwent 56 days of bed rest.
Ten volunteers were randomized to do resistive vibration exercise (RVE). The other 10 served as controls. RVE consisted of muscle contractions against resistance and concurrent whole-body vibration.
Main outcome parameters were maximal isometric plantar-flexion force (IPFF), electromyography (EMG)/force ratio, as well as jumping power and height. Measurements were obtained before and after bed rest, including a morning and evening assessment on the first day of recovery from bed rest. IPFF (-17.1%), jumping peak power (-24.1%), and height (-28.5%) declined (P < 0.05) in the control
group. There was a trend to EMG/force ratio decrease (-20%; P < 0.051). RVE preserved IPFF and mitigated the decline of countermovement jump performance (peak power -12.2%; height -14.2%). In both groups, IPFF was reduced between the two measurements of the first day of reambulation. This study indicates that bed rest and countermeasure exercises differentially affect the various functions of skeletal muscle. Moreover, the time course during recovery needs to
be considered more thoroughly in future studies, as IPFF declined not only with bed rest but also within the first day of reambulation. RVE was effective in maintaining IPFF but only mitigated the decline in jumping performance. More research is needed to develop countermeasures that maintain muscle strength as well as other muscle functions including power
Longitudinal changes in muscle power compared to muscle strength and mass
Objectives: The study reports longitudinal changes in grip strength, muscle mass and muscle power of lower extremities. The aim is to identify early muscular changes to improve the diagnosis and treatment of sarcopenia.
Methods: Grip strength was measured by hand dynamometer, muscle mass by dual-energy X-ray absorptiometry and muscle power by performing a chair rise test and two-leg jumps (2LJP) on the Leonardo Mechanograph®. Longitudinal changes were analysed using paired t-tests by age group and sex. Differences between groups in terms of the annual change were tested by Analysis of Variance and the Dunnett's test. Comparisons between the variables were performed using one sample t-tests.
Results: Six-year changes were determined in 318 randomly selected healthy participants aged 20-90 years from Berlin. 2LJP declined significantly earlier in 20-39 years old women (-3.70 W/kg) and men (-5.97 W/kg, both p<0.001). This is an absolute annual decline of -0.46 W/kg in females and -0.75 W/kg in males. In the oldest age group, 2LJP showed the highest absolute annual loss with -0.99 W/kg in women and -0.88 W/kg in men. 2LJP was significantly different compared to all variables of muscle mass and strength (p<0.01).
Conclusions: The results underline the importance of assessing muscle power using 2LJP during aging
In vivo bone remodeling rates determination and compressive stiffness variations before, during 60 days bed rest and two years follow up: A micro-FE-analysis from HR-pQCT measurements of the berlin Bed Rest Study-2
Bed rest studies are used for simulation and study of physiological changes as observed in unloading/non-gravity environments. Amongst others, bone mass reduction, similar as occurring due to aging osteoporosis, combined with bio-fluids redistribution and muscle atrophy have been observed and analyzed. Advanced radiological methods of high resolution such as HR-pQCT (XtremeCT) allow 3D-visualizing in vivo bone remodeling processes occurring during absence/reduction of mechanical stimuli (0 to <1 g) as simulated by bed rest. Induced bone micro-structure (e.g. trabecular number, cortical thickness, porosity) and density variations can be quantified. However, these parameters are average values of each sample and important information regarding bone mass distribution and within bone mechanical behaviour is lost. Finite element models with hexa-elements of identical size as the HR-pQCT measurements (0.082 mm×0.082 mm×0.082 mm, ca. 7E6 elements/sample) can be used for subject-specific in vivo stiffness calculation. This technique also allows quantifying if bone microstructural changes represent a risk of mechanical bone collapse (fracture). Materials and methods In the Berlin Bed Rest Study-2, 23 male subjects (20–50 YO) were maintained 60 days under restricted bed rest (6° HDT) aiming to test a - for this study specifically designed - vibration resistive exercise regime for maintenance of bone mass and muscle functionality at normal levels (base line measurements). For comparison a resistive exercise without vibration and a control group were included. Base line HR-pQCT measurements (3 days before bed rest: base line), as well as during 30 days bed rest (BR30 and BR59, 3 days of recovery (R3), R15, R30, R90, R180, R360, and R720 were performed. CT-scan voxels were converted into finite elements (hexa-82 µm edge length) for calculating in vivo compressive stiffness during the experiment duration. Histograms of stresses and strains distributions as well as anatomical regions susceptible for mechanical failure were identified and compared. Results: Resistive vibration exercises (RVE) were able to maintain in the majority of the subjects compressive bone strength as determined after modelling a compressive test using finite element models. Compressive bone stiffness using FEA was monitored through analysis of the internal deformation on the trabecular structures and cortical bone, reaction forces, and minimum principal strains on the in vivo CT measured bone regions during the experiment duration. Stress distributions (main stresses) and von Mises stress distribution remained comparable with those determined in the base line measurements for the RVE-group. However, no major differences were found in the group with resistive exercise training alone. Without mechanical stimuli an increment of bone regions with high stress concentration was observed and a reduction of up to 10% of bone compressive stiffness was quantified by using subject-specific finite-element analysis. Anatomically von Mises stress concentrations, thus bone regions susceptible to fail mechanically, were observed at the center of the cancellous bone and at the antero- posterior region of the cortical bone. Conclusions: Finite element simulations from bed rest studies are an invaluable tool to determine subject-specific in vivo compressive stiffness and anatomical mechanically compromised regions under controlled mechanical conditions (unloading) which - until now - are not possible to be determined with any other method. Vibration exercise combined with a resistive compressive force was able to maintain bone structure and density even during 60 days of bed rest
an RCT
Physical inactivity leads to a deconditioning of the skeletal, neuromuscular
and cardiovascular system. It can lead to impaired quality of life, loss of
autonomy, falls and fractures. Regular exercise would be a logical remedy, but
the generally recommended high-volume endurance and strength training programs
require a lot of time and equipment. In this randomized controlled study with
23 healthy participants, we established that a short, intensive jump training
program can prevent the large musculoskeletal and cardiovascular
deconditioning effects caused by two months of physical inactivity during bed
rest, particularly the loss of bone mineral mass and density, lean muscle
mass, maximal leg strength and peak oxygen uptake. The jump training group
showed no significant changes with respect to these indicators of
musculoskeletal and cardiovascular health after 60 days of bed rest, whereas
the control group exhibited substantial losses: up to −2.6% in tibial bone
mineral content and density, −5% in leg lean mass, −40% in maximal knee
extension torque and −29% in peak oxygen uptake. Consequently, we recommend
jump training as a very time-efficient and effective type of exercise for
astronauts on long-term space missions, the elderly and sedentary populations
in general
Secondary Osteoporosis: Endocrine and Metabolic Causes of Bone Mass Deterioration
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Secondary osteoporosis results from medical conditions or treatments that interfere with the attainment of peak bone mass and/or may predispose to accelerated bone loss. Although secondary osteoporosis is less common, it is becoming more frequently diagnosed. Apart from the welldefined risk of secondary osteoporosis in patients requiring long-term corticosteroids therapy, an increasing list of dietary, lifestyle, endocrine, metabolic, and other causes of bone mass deterioration has been identified (Table 1). Recently it has been demonstrated that, in contrast to primary osteoporosis which is associated with age, gender, and family history, secondary osteoporosis shows a prevalence in men similar to that in women (men 21 % versus women 17.5%
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