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Contains fulltext : 35772.pdf (Publisher’s version ) (Open Access) Several studies have tried to find countermeasures against musculoskeletal de-conditioning during bed-rest, but none of them yielded decisive results. We hypothesised that resistive vibration exercise (RVE) might be a suitable training modality. We have therefore carried out a bed-rest study to evaluate its feasibility and efficacy during 56 days of bed-rest. Twenty healthy male volunteers aged 24 to 43 years were recruited and, after medical check-ups, randomised to a non-exercising control (Ctrl) group or a group that performed RVE 11 times per week. Strict bed-rest was controlled by video surveillance. The diet was controlled. RVE was performed in supine position, with a static force component of about twice the body weight and a smaller dynamic force component. RVE comprised four different units (squats, heel raises, toe raises, kicks), each of which lasted 60 - 100 seconds. Pre and post exercise levels of lactate were measured once weekly. Body weight was measured daily on a bed scale. Pain questionnaires were obtained in regular intervals during and after the bed-rest. Vibration frequency was set to 19 Hz at the beginning and progressed to 25.9 Hz (SD 1.9) at the end of the study, suggesting that the dynamic force component increased by 90 %. The maximum sustainable exercise time for squat exercise increased from 86 s (SD 21) on day 11 of the BR to 176 s (SD 73) on day 53 (p = 0.006). On the same days, post-exercise lactate levels increased from 6.9 mmol/l (SD2.3) to 9.2 mmol/l (SD 3.5, p = 0.01). On average, body weight was unchanged in both groups during bed-rest, but single individuals in both groups depicted significant weight changes ranging from - 10 % to + 10 % (p < 0.001). Lower limb pain was more frequent during bed-rest in the RVE subjects than in Ctrl (p = 0.035). During early recovery, subjects of both groups suffered from muscle pain to a comparable extent, but foot pain was more common in Ctrl than in RVE (p = 0.013 for plantar pain, p = 0.074 for dorsal foot pain). Our results indicate that RVE is feasible twice daily during bed-rest in young healthy males, provided that one afternoon and one entire day per week are free. Exercise progression, mainly by progression of vibration frequency, yielded increases in maximum sustainable exercise time and blood lactate. In conclusion, RVE as performed in this study, appears to be safe.

Muscle atrophy and bone loss pose substantial problems for long-term space flight and in clinical immobilization. We therefore tested the efficacy of flywheel resistive exercise and pamidronate to counteract such losses. Twenty five young healthy males underwent strict bed rest with -6 degrees head-down tilt for 90 days. Subjects were randomized into an exercise group that practiced resistive exercise with a 'flywheel' (FW) device every 2-3 days, a pamidronate group (Pam) that received 60 mg pamidronate i.v. 14 days prior to bed rest and a control group (Ctrl) that received none of these countermeasures. During the study, Ca(++) and protein intake were controlled. Peripheral quantitative computed tomography (pQCT) was used to assess bone mineral content (BMC) and muscle cross sectional area (mCSA) of calf and forearm. Measurements were taken twice during baseline data collection, after 28 and after 89 days bed rest, and after 14 days recovery. On the same days, urinary Pyridinoline excretion and serum levels of alkaline phosphatase, Ca(++) and PTH were measured. Pre-study exercise habits were assessed through the Freiburg questionnaire. Losses in calf mCSA were significantly reduced in FW (Ctrl: -25.6% +/- 2.5% Pam: -25.6% +/- 3.7%, FW: -17.3% +/- 2.7%), but not in the forearm mCSA (Ctrl: -6.4% +/- 4.33%, Pam: -7.7% +/- 4.1%, FW: -7.6% +/- 3.3%). Both diaphyseal and epiphyseal BMC losses of the tibia were mitigated in Pam and FW as compared to Ctrl, although this was significant only at the diaphysis. Inter-individual variability was significantly greater for changes in BMC than in mCSA, and correlation of BMC losses was poor among different locations of the tibia. A significant positive correlation was found between change in tibia epiphyseal BMC and serum cortisol levels. These findings suggest that both countermeasures are only partly effective to preserve BMC (FW and Pam) and mCSA (FW) of the lower leg during bed rest. The partial efficacy of flywheel exercise as well as the bones' response to unloading per se underlines the importance of mechanical stimuli. The huge variability of BMC changes, however, suggests that other factors affect changes in whole-bone strength following acute mechanical disuse.

bjectives: To compare the reproducibility of the newly developed jumping mechanography with other physical tests. Design: Study 1: Repeated testing with an interval of 2 weeks to assess the short-term repetition error. Study 2: Testing on 5 successive days to assess learning effects. Setting: Geriatric clinic, Esslingen, Germany. Participants: Study 1 had 36 subjects aged 24 to 88; Study 2 had 22 subjects aged 19 to 86. Locomotor competence in all subjects was assessed using the ability to walk unaided and to perform a tandem stand and tandem walk. Measurements: The test battery consisted of timed up and go, freely chosen gait speed, maximum gait speed, chair-rising test, and maximum power in jumping mechanography. Results: All subjects performed the jumping mechanography without major problems. Study 1: Of all tests, maximum power in jumping mechanography depicted the smallest intrasubject short-term error (3.6%), the largest intersubject coefficient of variation (45.4%), and the greatest test-retest correlation coefficient (r=0.99). Study 2: The only tests for which the learning effects were confined to the 1% range were the maximum gait speed test and the maximum power in jumping mechanography. Conclusion: Assessment of maximum power in jumping mechanography appears to have good test-retest reliability with negligible learning effects. Moreover, it results in a comparatively large intersubject variability, which makes it an interesting method in the assessment of aging effects in middle-aged to older subjects and patients.

This cross-sectional study is based on images from the lower leg as assessed by peripheral quantitative computer tomography (pQCT). Measurements were performed in 39 female and 38 male control subjects and 15 female professional volleyball players, all between 18 and 30 years of age. The images were obtained at shank levels of 4%, 14%, 33%, and 66% from the distal end. Bone and muscle cross-sectional areas, and the bones' density-weighted area moment of resistance and of inertia were assessed. From these, muscle-bone strength indices (MBSIs) were developed for compression (CI = 100. bone area/muscle area) and bending (BI = 100. bone area moment of resistance/muscle area/tibia length). Significant correlations between muscle cross-sectional area and bone were found at all section levels investigated. The strongest correlation for compression was observed in the sections at 14% (correlation coefficient r = 0.74), where 4.10 +/- 0.46 cm(2) bone, on average, was related to 100 cm(2) muscle. The compression index (CI) at the 14% level was independent of the tibia length. Interestingly, the 15 athletes had significantly greater CIs than the control subjects. This is most probably due to the greater tension development in the athletes. The highest correlation for bending was for anteroposterior bending at 33% of tibia length (r = 0.81), where the area moment of resistance, R, was on, average, 4.21 +/- 0.54 cm(3)/100 cm(2) muscle/m tibia length. Analysis of the bones' area moment of inertia showed that buckling is a possible cause of bending at the 33% and 66% levels, but not at the 14% level. No gender differences in MBSI were found. Likewise, age was without significant effect. The data show that bone architecture depends critically on muscle cross section and tension development. Moreover, bone geometry (e.g., the tibia length) influences the geometrical distribution of bone mineral, as it was found that long bones adapted to the same compressive strength are wider than short ones. We conclude that MBSIs offer a powerful diagnostic tool for bone disorders and may contribute to improving the treatment of bone metabolic and other diseases.

Contains fulltext : 89644.pdf (Publisher’s version ) (Closed access) Bed rest is a recognized model for muscle atrophy and bone loss in space flight and in clinical medicine. We hypothesized that whole body vibration in combination with resistive exercise (RVE) would be an effective countermeasure. Twenty healthy male volunteers underwent horizontal bed rest for 56 days and were randomly assigned either to a group that performed RVE 11 times per week or to a group that underwent bed rest only (Ctrl). Bone mineral content (BMC) was assessed by peripheral quantitative computed tomography (pQCT) in the tibia and the radius and by dual x-ray absorptiometry (DXA) in the hip and lumbar spine at baseline and at regular intervals during bed rest and a 12-month follow-up. RVE appeared to protect muscle size and function, and it also prevented bone loss (p-values between

Mechanical loads cause bone strains; and muscle forces, not body weight, cause the largest strains. The strains help to control the effects of bone modeling and remodeling on bone strength and "mass." When strains exceed a threshold range, modeling increases bone strength and "mass." When strains stay below a smaller threshold range, remodeling begins removing bone next to marrow. As a result, increasing muscle strength increases bone strength and "mass," and decreasing muscle strength decreases bone strength and "mass." Estrogen apparently lowers the remodeling threshold, which reduces bone losses. Loss of estrogen raises that threshold to cause losses of bone next to marrow. Such facts help to explain: 1.Bone loss in aging adults. 2.An increase in bone "mass" in girls at menarche. 3.The loss of bone during menopause. 4.The greater bone "mass" in obese than in slender subjects, and in weightlifters than in marathon runners. 5.And the pathogenesis of physiologic osteopenias and true osteoporoses. Thus new standards are needed for the relationships between bone and muscle strengths, and as functions of sex, age, race, disease, endocrine status, nutrition, vitamin and mineral intakes, medications, puberty, and menopause. Obtaining those standards and studying such relationships provide many new opportunities for studies that involve dual energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) and, perhaps some day, ultrasound and magnetic resonance imaging (MRI) techniques.

Ageing compromises locomotor capacity and is associated with an increased risk of falls. Several lines of evidence indicate that both changes in muscle mass and performance are causative. Most studies, however, do not discern between effects of ageing, sedentarism and comorbidity. The present study compares the age effects in muscle cross section, force and power in physically competent self-selected subjects of different age groups. A total of 169 women and 89 men between 18 and 88 years, without any disease, impairment or medication affecting the musculoskeletal system were enrolled in this study. Calf muscle cross-sectional area was assessed by computed tomography. Muscle force and power were assessed by jumping mechanography. No significant correlation between muscle cross section and age was found in the men. A weak correlation in the women disappeared after correction for height. Close correlations with age, however, were found for peak force and peak power. Correction for muscle cross section or body weight further increased these correlation coefficients, particularly for peak power specific to body weight (r = 0.81 in women and r = 0.86 in men). The non-sedentarian population investigated here depicted a reduction of >50% between the age of 20 and 80 without a reduction in muscle cross section. This suggests a crucial role for muscular power in the ageing process. Possibly, the jumping mechanography as a measurement of anti-gravitational power output is a promising extension of the chair-rising test, known to be predictive for immobilization and the risk of falls.

To compare the reproducibility of the newly developed jumping mechanography with other physical tests.Study 1: Repeated testing with an interval of 2 weeks to assess the short-term repetition error. Study 2: Testing on 5 successive days to assess learning effects.Geriatric clinic, Esslingen, Germany.Study 1 had 36 subjects aged 24 to 88; Study 2 had 22 subjects aged 19 to 86. Locomotor competence in all subjects was assessed using the ability to walk unaided and to perform a tandem stand and tandem walk.The test battery consisted of timed up and go, freely chosen gait speed, maximum gait speed, chair-rising test, and maximum power in jumping mechanography.All subjects performed the jumping mechanography without major problems. Study 1: Of all tests, maximum power in jumping mechanography depicted the smallest intrasubject short-term error (3.6%), the largest intersubject coefficient of variation (45.4%), and the greatest test-retest correlation coefficient (r=0.99). Study 2: The only tests for which the learning effects were confined to the 1% range were the maximum gait speed test and the maximum power in jumping mechanography.Assessment of maximum power in jumping mechanography appears to have good test-retest reliability with negligible learning effects. Moreover, it results in a comparatively large intersubject variability, which makes it an interesting method in the assessment of aging effects in middle-aged to older subjects and patients.

In this study we investigated metabolic power during whole-body vibration exercise (VbX) compared to mild resistance exercise. Specific oxygen consumption ( % MathType!MTEF!2!1!+- % feaaeaart1ev0aqatCvAUfKttLearuavP1wzZbqedmvETj2BSbWexL % MBbXgBcf2CPn2qVrwzqf2zLnharyWqVvNCPvMCG4uz3bqee0evGueE % 0jxyaibaieYlf9irVeeu0dXdh9vqqj-hEeeu0xXdbba9frFj0-OqFf % ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr % 0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaiqbdAfawzaaca % Gaee4ta80aaSbaaSqaaiabbkdaYaqabaaaaa!386A! $\dot V{\rm O}_{\rm 2} $ ) and subjectively perceived exertion (rating of perceived exertion, RPE; Borg scale) were assessed in 12 young healthy subjects (8 female and 4 male). The outcome parameters were assessed during the last minute of a 3-min exercise bout, which consisted of either (1) simple standing, (2) squatting in cycles of 6 s to 90° knee flexion, and (3) squatting as before with an additional load of 40% of the subject's body weight (35% in females). Exercise types 1–3 were performed with (VbX+) and without (VbX–) platform vibration at a frequency of 26 Hz and an amplitude of 6 mm. Compared to the VbX– condition, the specific % MathType!MTEF!2!1!+- % feaaeaart1ev0aqatCvAUfKttLearuavP1wzZbqedmvETj2BSbWexL % MBbXgBcf2CPn2qVrwzqf2zLnharyWqVvNCPvMCG4uz3bqee0evGueE % 0jxyaibaieYlf9irVeeu0dXdh9vqqj-hEeeu0xXdbba9frFj0-OqFf % ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr % 0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaiqbdAfawzaaca % Gaee4ta80aaSbaaSqaaiabbkdaYaqabaaaaa!386A! $\dot V{\rm O}_{\rm 2} $ was increased with vibration by 4.5 ml·min–1·kg–1. Likewise, squatting and the additional load were factors that further increased % MathType!MTEF!2!1!+- % feaaeaart1ev0aqatCvAUfKttLearuavP1wzZbqedmvETj2BSbWexL % MBbXgBcf2CPn2qVrwzqf2zLnharyWqVvNCPvMCG4uz3bqee0evGueE % 0jxyaibaieYlf9irVeeu0dXdh9vqqj-hEeeu0xXdbba9frFj0-OqFf % ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr % 0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaiqbdAfawzaaca % Gaee4ta80aaSbaaSqaaiabbkdaYaqabaaaaa!386A! $\dot V{\rm O}_{\rm 2} $ . Corresponding changes were observed in RPE. There was a correlation between VbX– and VbX+ values for exercise types 1–3 (r=0.90). The correlation coefficient between squat/no-squat values (r=0.70 without and r=0.71 with the additional load) was significantly lower than that for VbX–/VbX+. Variation in specific % MathType!MTEF!2!1!+- % feaaeaart1ev0aqatCvAUfKttLearuavP1wzZbqedmvETj2BSbWexL % MBbXgBcf2CPn2qVrwzqf2zLnharyWqVvNCPvMCG4uz3bqee0evGueE % 0jxyaibaieYlf9irVeeu0dXdh9vqqj-hEeeu0xXdbba9frFj0-OqFf % ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr % 0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaiqbdAfawzaaca % Gaee4ta80aaSbaaSqaaiabbkdaYaqabaaaaa!386A! $\dot V{\rm O}_{\rm 2} $ was significantly higher in the squatting paradigm than with vibration. It is concluded that the increased metabolic power observed in association with VbX is due to muscular activity. It is likely that this muscular activity is easier to control between individuals than is simple squatting.

This study analyses the evaluation of tomographic indicators of tibia structure, assuming that the usual loading pattern shifts from uniaxial compression close to the heel to a combined compression, torsion and bending scheme towards the knee. To this end, pQCT scans were obtained at 5% intervals of the tibia length (S5–S95 sites from heel to knee) in healthy men and women (10 ⁄ 10) aged 20–40 years. Indicators of bone mass [cortical area, cortical ⁄ total bone mineral content (BMC)], diaphyseal design (peri ⁄ endosteal perimeters, cortical thickness, circularity, bending ⁄ torsion moments of inertia – CSMIs), and material quality [(cortical vBMD (bone mineral density)] were determined. The longitudinal patterns of variation of these measures were similar between genders, but male values were always higher except for cortical vBMD. Expression of BMC data as percentages of the minimal values obtained along the bone eliminated those differences. The correlative variations in cortical area, BMC and thickness, periosteal perimeter and CSMIs along the bone showed that cortical bone mass was predominantly associated with cortical thickness toward the mid-diaphysis, and with bone diameter and CSMIs moving more proximally. Positive relationships between CSMIs (y) and total BMC (x) showed men’s values shifting to the upper-right region of the graph and women’s values shifting to the lower-left region. Total BMC decayed about 33% from S5 to S15 (where minimum total BMC and CSMI values and variances and maximum circularity were observed) and increased until S45, reaching the original S5 value at S40. The observed gender-related differences reflected the natural allometric relationships. However, the data also suggested that men distribute their available cortical mass more efficiently than women. The minimum amount and variance of mass indicators and CSMIs, and the largest circularity observed at S15 reflected the assumed adaptation to compression pattern at that level. The increase in CSMIs (successively for torsion, A–P bending, and lateral bending), the decrease in circularity values and the changes in cortical thickness and periosteal perimeter toward the knee described the progressive adaptation to increasing torsion and bending stresses. In agreement with the biomechanical background, the described relationships: (i) identify the sites at which some changes in tibial stresses and diaphyseal structure take place, possibly associated with fracture incidence; (ii) allow prediction of mass indicators at any site from single determinations; (iii) establish the proportionality between the total bone mass at regions with highly predominant trabecular and cortical bone of the same individual, suitable for a specific evaluation of changes in trabecular mass; and (iv) evaluate the ability of bone tissue to self-distribute the available cortical bone according to specific stress patterns, avoiding many anthropometric and gender-derived influences.