Introduction/Aims The ability of low intensity vibration (LIV) to combat skeletal decline in Duchenne Muscular Dystrophy (DMD) was evaluated in a randomized controlled trial.Methods Twenty DMD boys were enrolled, all ambulant and treated with glucocorticoids (mean age 7.6, height-adjusted Z-scores (HAZ) of hip BMD −2.3). Ten DMD boys were assigned to stand for 10min/d on an Active LIV platform (0.4g @ 30Hz), while 10 stood on a Placebo device. Baseline and 14-month BMC and BMD of spine, hip and total body were measured with DXA, and trabecular bone density (TBD) of tibia with QCT.Results All children tolerated the LIV intervention well, with daily compliance averaging 78%. At 14 months, TBD in the proximal and distal tibia remained unchanged in Placebo (−0.7% & −0.8%), while rising 4.1% and 4.5% in LIV. HAZ for hip BMD and BMC in Placebo declined 22% and 13% respectively, contrasting with no change from baseline (0.9% and 1.4%) in LIV. Fat mass in the leg increased 33% in Placebo, contrasting with 20% in LIV subjects. Across the 14-month study, there were four incident fractures in three placebo patients (30%), with no new fractures identified in LIV subjects.Conclusions These data suggest that non-invasive LIV can help protect the skeleton of DMD children against the disease progression, the consequences of diminished load bearing, and the complications of chronic steroid use.### Competing Interest StatementCTR and SJ have several US and International patents issued on the use of low intensity vibration for the treatment of musculoskeletal injury and disease. CTR is also a founder of Marodyne, Inc, who developed the LIV platform for clinical use as LivMD. No other authors have any conflicts to report.### Clinical TrialNCT05281120### Funding StatementWe are grateful to the Istituto Auxologico Italiano IRCCS, Milan, Italy, for providing funding for the study, and to Mr. Ian Cutts, COPA Healthcare, for the generous loan of the prototype LIV devices.### Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:IRB of Istituto Auxologico Italiano IRCCS, Milan, Italy, gave ethical approval for this work.I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).YesI have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.YesAll data produced in the present study are available upon reasonable request to the authors

Patients afflicted with or being treated for cancer constitute a distinct and alarming subpopulation who exhibit elevated fracture risk and heightened susceptibility to developing secondary osteoporosis. Cancer cells uncouple the regulatory processes central for the adequate regulation of musculoskeletal tissue. Systemically taxing treatments to target tumors or disrupt the molecular elements driving tumor growth place considerable strain on recovery efforts. Skeletal tissue is inherently sensitive to mechanical forces, therefore attention to exercise and mechanical loading as non-pharmacological means to preserve bone during treatment and in post-treatment rehabilitative efforts have been topics of recent focus. This review discusses the dysregulation that cancers and the ensuing metabolic dysfunction that confer adverse effects on musculoskeletal tissues. Additionally, we describe foundational mechanotransduction pathways and the mechanisms by which they influence both musculoskeletal and cancerous cells. Functional and biological implications of mechanical loading at the tissue and cellular levels will be discussed, highlighting the current understanding in the field. Herein, in vitro, translational, and clinical data are summarized to consider the positive impact of exercise and low magnitude mechanical loading on tumor-bearing skeletal tissue.

Ovariectomized mice were used to assess the ability of low-intensity vibrations to protect bone microarchitecture and marrow composition. Results indicate that low-intensity vibrations (LIV), introduced 2 weeks postsurgery, slows marrow adipogenesis in OVX mice but does not restore the bone within the period studied. However, immediate application of LIV partially protects quality.

We sought to determine whether low-magnitude mechanical stimulation (LMMS) normalizes bone turnover among adolescents hospitalized for anorexia nervosa (AN). Brief, daily LMMS prevents the decline in bone turnover typically seen during bed rest in AN. LMMS may have application for patients with AN in the inpatient setting to protect bone health.

Non-invasive three-dimensional imaging of live rodents is a powerful research tool that has become critical for advances in many biomedical fields. For investigations into adipose development, obesity, or diabetes, accurate and precise techniques that quantify adiposity in vivo are critical. Because total body fat mass does not accurately predict health risks associated with the metabolic syndrome, imaging modalities should be able to stratify total adiposity into subcutaneous and visceral adiposity. Micro-computed tomography (micro-CT) acquires high-resolution images based on the physical density of the material and can readily discriminate between subcutaneous and visceral fat. Here, a micro-CT based method to image the adiposity of live rodents is described. An automated and validated algorithm to quantify the volume of discrete fat deposits from the computed tomography is available. Data indicate that scanning the abdomen provides sufficient information to estimate total body fat. Very high correlations between micro-CT determined adipose volumes and the weight of explanted fat pads demonstrate that micro-CT can accurately monitor site-specific changes in adiposity. Taken together, in vivo micro-CT is a non-invasive, highly quantitative imaging modality with greater resolution and selectivity, but potentially lower throughput, than many other methods to precisely determine total and regional adipose volumes and fat infiltration in live rodents.

Bone formation and resorption are sensitive to both external loads arising from gravitational loading as well to internal loads generated by muscular activity. The question as to which of the two sources provides the dominant stimulus for bone homeostasis and new bone accretion is arguably tied to the specific type of activity and anatomical site but it is often assumed that, because of their purportedly greater magnitude, muscle loads modulate changes in bone morphology. High-frequency mechanical signals may provide benefits at low-(1 g) and high- (>1 g) acceleration magnitudes. While the mechanisms by which cells perceive high-frequency signals are largely unknown, higher magnitude vibrations can cause large muscle loads and may therefore be sensed by pathways similar to those associated with exercise. Here, we review experimental data to examine whether vibrations applied at very low magnitudes may be sensed directly by transmittance of the signal through the skeleton or whether muscle activity modulates, and perhaps amplifies, the externally applied mechanical stimulus. Current data indicate that the anabolic and anti-catabolic effects of whole body vibrations on the skeleton are unlikely to require muscular activity to become effective. Even high-frequency signals that induce bone matrix deformations of far less than five microstrain can promote bone formation in the absence of muscular activity. This independence of cells on large strains suggests that mechanical interventions can be designed that are both safe and effective.

A mouse model of spinal muscular atrophy with respiratory distress (SMARD1) was used to study the consequences of neuromuscular degenerative disease on bone quantity and morphology. Histomorphometry and micro-computed tomography were used to assess the cortical and cancellous bone in the tibia, femur and humerus of adult neuromuscular degeneration (nmd) mice (up to 21w) and age-matched wild-type controls (WT). At 21w, the average lengths of the humerus, tibia and femur were 15%, 10%, and 10% shorter in the nmd mice, respectively. The midshaft of the humerus, tibia and femur of nmd mice had 41%, 47% and 34% less cortical bone than the WT. In the humeral, tibial, and femoral metaphyses of the nmd mice, there was 50%, 78%, and 85% less trabecular bone volume, and 58%, 92%, and 94% less trabecular connectivity than the WT. NMD cortical bone had less than half of the 42% active surface measured in the WT, yet the mineral apposition rate of those surfaces were similar between strains (nmd: 1.80 microm x day(-1); WT: 2.05 microm x day(-1)). Osteoclast number and activity levels did not differ across strains. These data emphasize that neuromuscular degeneration as a result of immunoglobulin S-mu binding protein-2 (Ighmbp2) mutation will compromise several critical parameters of bone quantity and architecture, the most severe occurring in the trabecular compartment.

The age-induced decline in the body's ability to fight disease is exacerbated by obesity and metabolic disease. Using a mouse model of diet-induced obesity, the combined challenge of a high-fat diet and age on liver morphology and biochemistry was characterized, while evaluating the potential of 15 min per day of high frequency (90 Hz), extremely low-magnitude (0.2 G) mechanical signals (LMMS) to suppress lipid accumulation in the liver. Following a 36-week protocol (animals 43 weeks of age), suppression of hepatomegaly and steatosis was reflected by a 29% lower liver mass in LMMS animals as compared with controls. Average triglyceride content was 101.7±19.4 μg mg−1 tissue in the livers of high-fat diet control (HFD) animals, whereas HFD+LMMS animals realized a 27% reduction to 73.8±22.8 μg mg−1 tissue. In HFD+LMMS animals, liver free fatty acids were also reduced to 0.026±0.009 μEq mg−1 tissue from 0.035±0.005 μEq mg−1 tissue in HFD. Moderate to severe micro- and macrovesicular steatosis in HFD was contrasted to a 49% reduction in area covered by the vacuoles of at least 15 μm2 in size in HFD+LMMS animals. These data provide preliminary evidence of the ability of LMMS to attenuate the progression of fatty liver disease, most likely achieved indirectly by suppressing adipogenesis and thus the total adipose burden through life, thereby reducing a downstream challenge to liver morphology and function.

Accurate and precise techniques that identify the quantity and distribution of adipose tissue in vivo are critical for investigations of adipose development, obesity, or diabetes. Here, we tested whether in vivo micro-computed tomography (microCT) can be used to provide information on the distribution of total, subcutaneous and visceral fat volume in the mouse. Ninety C57BL/6J mice (weight range: 15.7-46.5 g) were microCT scanned in vivo at 5 months of age and subsequently sacrificed. Whole body fat volume (base of skull to distal tibia) derived from in vivo microCT was significantly (p<0.001) correlated with the ex vivo tissue weight of discrete perigonadal (R(2)=0.94), and subcutaneous (R(2)=0.91) fat pads. Restricting the analysis of tissue composition to the abdominal mid-section between L1 and L5 lumbar vertebrae did not alter the correlations between total adiposity and explanted fat pad weight. Segmentation allowed for the precise discrimination between visceral and subcutaneous fat as well as the quantification of adipose tissue within specific anatomical regions. Both the correlations between visceral fat pad weight and microCT determined visceral fat volume (R(2)=0.95, p<0.001) as well as subcutaneous fat pad weight and microCT determined subcutaneous fat volume (R(2)=0.91, p<0.001) were excellent. Data from these studies establish in vivo microCT as a non-invasive, quantitative tool that can provide an in vivo surrogate measure of total, visceral, and subcutaneous adiposity during longitudinal studies. Compared to current imaging techniques with similar capabilities, such as microMRI or the combination of DEXA with NMR, it may also be more cost-effective and offer higher spatial resolutions.

Genetic variations are a principal factor controlling bone morphology and mechanosensitivity. Genetically distinct inbred strains of mice provide an effective model to separate genetic from epigenetic factors. For example, BALE/cByJ mice not only have different morphology than C3H mice, but also lose most of their trabecular bone volume in the femur during disuse while C3H mice are comparatively unresponsive. Double-crossing these two strains, and thus generating a new population of mice with a wide range mechanosensitivity, allows the identification of the specific chromosomal regions that define the (distinct) response of the tissue to an environmental stimulus. Here, we report disuse-induced changes in femoral mid-diaphysial morphology of F2 mice population that were scanned by in-vivo muCT at baseline, upon 3wk disuse and 3wk of subsequent reambulation. Results indicate heterogeneous population was achieved for both baseline morphology and mechanosensitivity (longitudinal change during disuse and upon reambulation). Preliminary QTL maps indicate several chromosomal regions that may be responsible for the skeletal morphology.

Obesity, a global pandemic that debilitates millions of people and burdens society with tens of billions of dollars in health care costs, is deterred by exercise. Although it is presumed that the more strenuous a physical challenge the more effective it will be in the suppression of adiposity, here it is shown that 15 weeks of brief, daily exposure to high-frequency mechanical signals, induced at a magnitude well below that which would arise during walking, inhibited adipogenesis by 27% in C57BL/6J mice. The mechanical signal also reduced key risk factors in the onset of type II diabetes, nonesterified free fatty acid and triglyceride content in the liver, by 43% and 39%, respectively. Over 9 weeks, these same signals suppressed fat production by 22% in the C3H.B6-6T congenic mouse strain that exhibits accelerated age-related changes in body composition. In an effort to understand the means by which fat production was inhibited, irradiated mice receiving bone marrow transplants from heterozygous GFP+ mice revealed that 6 weeks of these low-magnitude mechanical signals reduced the commitment of mesenchymal stem cell differentiation into adipocytes by 19%, indicating that formation of adipose tissue in these models was deterred by a marked reduction in stem cell adipogenesis. Translated to the human, this may represent the basis for the nonpharmacologic prevention of obesity and its sequelae, achieved through developmental, rather than metabolic, pathways.

The development of obesity and diabetes is often attributable to a sedentary lifestyle, with a common therapeutic intervention being exercise.1 While the presumption has been that more strenuous workouts are more effective in the suppression of adipogenesis, here we show that 15 weeks of brief, daily exposure to high frequency, low magnitude mechanical signals suppresses adipogenesis by 26% in the young adult mouse. Concomitant with this decrease in fat, we observe an increase in both lean volume and bone volume of the animal. Biochemically, this mechanical signal reduces non-esterified free fatty acid and triglyceride content in the liver by 43% and 39%, respectively. The applied signal is induced at a magnitude well below that which would arise during walking and is relatively short in duration. The brevity and low intensity of this mechanical intervention suggests a powerful means of inhibiting the formation of adipose tissue, and subsequently lowering free fatty acid and triglyceride content in several key tissues.