Intervention on Bone Health in Wheelchair Users

Inclusion Criteria: * BMD Z-score of the spine ≤ 0 SD * primary aid for mobility being a manual wheelchair, i.e. ≥50% of the time * 18-60 Y * congenital (i.e., CP, spina bifida, dysmelia, hip dysplasia) and acquired disabilities (i.e., SCI, amputation) * non-progressive impairment, and in the case of SCI; ≥ 2 years since time of injury * ability to perform key exercises (e.g., overhead press) Exclusion Criteria: * injury acquired \<2 Y ago * change in health and/or medication within the last 3 months * fractures affecting measured sites or contraindicating strength testing/training * menopausal, pregnancy or planned pregnancy during the study period * language or cognitive barriers affecting the ability to understand all aspects of the study * • patients with progressive neurological disease, serious or uncontrollable epilepsy, endocrine diseases (including diabetes mellitus type 1 or 2, thyroid disorders, calcium homeostasis disorders and metabolic bone disease, pituitary gland disorder, sex hormone disorders), cancer, serious mental disorder, or comorbid medical conditions affecting either a) nutritional function: i.e., malabsorption problems due to previous surgery in the gastrointestinal tract, inflammatory bowel disease, coeliac disease, eating disorders, chronic pancreatitis, liver or kidney disease (those that cannot convert vitamin D to its active form in the body), other conditions affecting vitamin D or calcium absorption; b) musculoskeletal system: i.e., congenital systemic skeletal dysplasia affecting bone density, inflammatory arthritis conditions (such as rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, and lupus), ongoing tendinitis or muscle injuries not compatible with the exercise intervention; c) cardiovascular system: i.e. congenital heart failure, congenital connective tissue disorders affecting the aorta and/or arteries, other cardiovascular conditions not compatible with the exercise intervention; * the use of certain medications: bisphosphonates, PTH (teriparatide), Denosumab, Raloksiphen, Prednisolone/steroids/androgenic steroids, high dose oestrogen (including medroxyprogesterone acetate contraceptives) immunosuppressive medications/ chemotherapies, vitamin K, anti-epileptic medication (Lamotrigine, Phenytoin, Phenobarbital, Carbamazepine, Primidone), proton pump inhibitors (PPIs), selective serotonin receptor inhibitors (SSRIs), thiazolidinediones (TZDs), anticonvulsants, hormone deprivation therapy, calcineurin inhibitors, and isotretinoin. * other therapies that aim to increase bone mineral density, e.g., vibration therapy, functional electrical stimulation (FES) * alternative medicine that interfere with vitamin D or calcium metabolism or affect bone mineral density * known other contraindication of resistance exercise.