The study will be single blinded since professionals who will evaluate patients will not know to which exercise group patients have been assigned.

The investigators hypothesize that effectiveness and safety of the exercise program are equal when administered as gym trainer or individual home trainer. However, the investigators expect differences in adherence among the two groups which may cause different impact on the outcome measures.

Given the large amount of evidence on the efficacy of Physical Activity in women with Osteoporosis, the investigators considered it ethically unacceptable to advise a control group inactivity. On the other hand, it seemed particularly relevant for the purpose of addressing the advice to the improvement of the active lifestyle, to evaluate the impact of the ACTLIFE exercise program when administered as gym trainer or individual home trainer

The present study is carried out within the project "Physical ACTivity: the tool to improve the quality of LIFE in osteoporosis people" (ACTLIFE) and is funded within the Erasmus Plus Sport program (Grant Agreement N2017-2128/001-001).

It is aimed at evaluating differences in efficacy and safety of a PA program specifically designed for improving physical function and, here in after, QoL in post menopausal women with Osteoporosis (T-score <-2,5) under usual pharmacological treatment, when administered as gyms as group training (GGT) or Individual Home Training IHT. During the study patients will be recommended to maintain their usual pharmacological treatment for OP, as prescribed.

The primary objective of the study is to compare modifications of QoL measured with the Short Osteoporosis Quality of Life Questionnaire (ECOS-16) induced by the ACTLIFE exercise programme when administered as IHT or GGT. ECOS-16 is a specific-disease instrument with the purpose to measure the health related QoL (HRQoL) in post menopausal women with OP.

The secondary objectives of the study are to investigate differences between IHT and GGT on domains which are considered to be determinants of QoL:

• WHO Disability Assessment Schedule (WHODAS) which evaluates the six activity and participation domains of the International Classification of Functioning, Disability and Health (ICF): cognition, mobility, self-care, interacting with other people, life activities, participation.
• Fear of falls evaluated by the Falls Efficacy Scale International (FES-I);
• Walking (6-Minute Walk Test), standing balance (stability Index), muscle force (hand grip), postural alignment (occiput-wall distance) and joint mobility will be also evaluated as fundamental prerequisites of motor behavior;
• Body Mass index and body composition.

The adherence of each patient to the exercise program will be monitored. The adherence will be measured as percent of exercise sessions actually performed /total number of scheduled exercise sessions. The investigators hypothesize that effectiveness and safety of the exercise program are equal when administered as GGT or IHT. However, the investigators expect differences in adherence among the two groups which may cause different impact on the outcome measures. In the context of the evaluation of adherence to the program, the satisfaction of the participants for the ACTLIFE program administered as GGT or IHT at the end of the 12 months of exercise will be evaluated with a specific questionnaire based on 7-point Likert scale and the reasons of abandoning the exercise program (question with structured answers). Education attainment, work activity, marital status and home-gym distance will be also recorded since recognized to influence the adherence in an exercise program.

The ultimate goal of the ACTLIFE exercise program is to increase physical activity in a sedentary population. The exercise program, through its beneficial effects on health, is expected to generate a virtuous circle of greater activity and participation. In this context, to evaluate differences between GGT or IHT, the investigators introduced in the study protocol the Physical Activity Scale for the Elderly (PASE). PASE is an easily scored survey designed specifically to measure the weekly physical activity in adult and aged population. Its score combines information on leisure, household and occupational activity.

RT with two parallel groups: in the first group the 12-month ACTLIFE program is performed as IHT, while in the second as GGT. The study will be single blinded since professionals who will evaluate patients will not know to which exercise group they have been assigned. Patients will be assessed at baseline and after 6 and 12 months.

Inclusion Criteria:

• signed informed consent
• post menopausal women aged >40 years (with or without history of fractures, with or without pharmacological therapy for OP)
• lumbar spine or femur T-score ≤-2,5
• functional motor capacity normal or moderately reduced (Short Physical Performance Battery)
• sedentary life style (having exercised less than 30 minutes per week in the last 6 months).

Exclusion Criteria are:

• secondary OP49, impairment of communicative and/or sensorial functions so severe to make impossible understanding or executing trainer's instructions (dementia, aphasia, blindness, deafness);
• heart failure (NYHA class >2);
• unstable angina, pulmonary disease requiring oxygen therapy;
• symptomatic peripheral arteriopathy;
• myocardial infarction or hospital admission in the previous 6 months,
• symptomatic orthostatic hypotension;
• hypertension in poor pharmacologic control (diastolic >95 mmHg, systolic >160 mmHg),
• previous implant of prosthesis at upper or lower limbs,
• relevant neurological condition impairing motor or cognitive function, any other condition that the medical doctor (MD) considers to contraindicate the participation in an exercise program of moderate intensity.