## 2 Materials and Methods  
A randomized, triple blinded, controlled, three-group parallel pilot study was designed. The 2010 Consolidated Standards of Reporting Trials (CONSORT) guidelines were used [25]. All participants were allocated 1:1 to either one of the four protocols of different orders of frequencies of mechanical vibrations upon enrollment (Figure 1). This study was planned and designed with the international ethical guidelines for a clinical study. The research project was approved by the _Comissao Nacional de Etica em Pesquisa/Certificado de apresentacao para Apreciacao Etica_ number 48116215.0.0000.5259. This clinical trial was registered in the Brazilian Clinical Trial Registry (ReBEC): RBR-2b4b2q (www.ensaiosclinicos.gov.br) according to international guidelines. A sample size calculation (8 = 0.10) based on detecting a minimum of 20% of difference in sEMGrms of vastus lateralis (VL) (SD = 10) between the interventions, showed that at a 5% significance level would require a sample of 5 participants in groups with a power of 90% [26]. The lupus individuals were recruited from the Rheumatology Department of the _Universidade do Estado do Rio de Janeiro_ (UERJ) in Rio de Janeiro, Brazil and were divided in two groups, SLE with OP or osteopenia (OPIA) (SLE OPIA) and SLE without OP or OPIA (SLE). They were all female outpatients undergoing their regular medical consultations on the lupus ambulatory, whom, after a brief interview, were invited to participate. Consenting patients were included if they were older than 40 years, diagnosed with SLE at least three years previously [27] and were regularly using glucocorticoids (prednisone or similar). The subjects must have been stable on lupus therapy, without recent increments on medications, with low index of disease activity and not having a disease flare according to clinical charts and the referring rheumatologist. All the medications for comorbidities were recorded, including diuretics and statins. The non-lupus female participants (CG) were invited to the Rheumatology Department among the lupus patient acquaintances when the patients had their regular consultations at the hospital. They were interviewed and excluded if they had any inflammatory rheumatic disease or if they were regularly using GC. Patients were excluded if they smoked, had a history of alcohol abuse, history of low impact fractures, if they were using assistive walking devices, had hip or knee joint replacement surgery, and if they were pregnant. They were also excluded if their comorbidities could potentially be affected by the PE, and if there was presence of neurological or psychiatric disease that caused fear to the movements on the VP. The participants of all three groups (SLE OPIA, SLE and CG) who were eligible to participate and signed the informed consent were submitted to a dual X-ray absorptiometry (DXA). The scans assessed bone mineral density (BMD), T and Z scores of the right hip, lumbar spine (L1-L4), and total body. The T and or Z scores equal or less than \(-\)1.01 standard deviations (SD) in any of the regions of interest (ROI) were considered as compromise of bone mass as osteopenia is defined [28]. Subjects with SLE and loss of bone mass were classified to the SLE OPIA group. The lupus individuals without impairment of bone mass were allocated in the SLE group. The CG group was exclusively composed of non-lupus and non-bone mass reduction female individuals. If non-lupus participants had impairment of bone mass, they were excluded from the CG. The regional and total lean/fat mass and derived indexes were obtained through analysis of whole body DXA [29; 30; 31]. For body mass index (BMI), the following ranges were used: normal, BMI = 18.5-24.9 kg/m\({}^{2}\); overweight, BMI = 25-29.9 kg/m\({}^{2}\); and obesity, BMI \(\geq\) 30 kg/m\({}^{2}\), as recommended by the World Health Organization [32]. DXA body fat percentage (BF%) above 39% was considered to represent obesity since it has been demonstrated that in obese women, it ranges from 39 to 43%.