The Proto-Aging study aims to define experimental protocols and guidelines to enable the development of musculoskeletal models (digital twins) of elderly people, with the ultimate goal to comprehensively characterize frail elders from a biomechanical standpoint.

It is typical for the elderly to present with weakness, slowed movements and reduced levels of physical activity, all of which may be related to the loss of muscle force (dynapenia). Unfortunately, to date, the primary cause for dynapenia is difficult to identify. Digital twins may help to this end, but their development remains critical as it requires a specialized skillset and experimental data for model personalisation.

In this study, where the investigators will recruit a small group of frail elders and a cohort of healthy young individuals, all participants will undergo the following examinations: (i) gait assessment, (ii) maximal voluntary isometric contraction (MVIC) test, (iii) superimposed neuromuscular electrical stimulation, and (iv) full lower limb magnetic resonance imaging. Surface electromyography data will further be collected while the subjects perform both the gait assessment and the MVIC test. Last, clinical questionnaires will be administered, and the subjects will be asked to perform additional clinical measures (i.e., hand-grip test, bioelectrical impedance analysis).

At the end of the study, a reduced version of the experimental protocol will be developed, with the intent to provide clinicians with a protocol that can be deployed in clinical settings, accounting for the observed reliability and repeatability of each measure, the required level of expertise, and the associated costs and time expenditure.

Inclusion Criteria:

• Age: 65-80 years
• Body Mass Index between 18.5 and 30 kg/m2
• Frailty syndrome diagnosed according to Fried's criteria (i.e., at least three of the following items: unintended loss of weight, weakness, self-reported exhaustion, slow walking speed, low level of physical activity)

Exclusion Criteria:

• Any musculoskeletal, neurological, rheumatic or tumoral diseases
• Dementia
• Diabetes
• Inguinal or abdominal hernia
• Severe Hypertension (Level 3)
• Severe Cardio-pulmonary insufficiency
• Diagnosis of Osteonecrosis in the lower limb joints
• Pathologies or physical conditions incompatible with the use of magnetic resonance imaging and electrostimulation (i.e., active and passive implanted biomedical devices, epilepsy, severe venous insufficiency in the lower limbs)
• Previous interventions or traumas to the joints of the lower limb

NOTE: A group of healthy volunteers, who meet the following criteria, will be enrolled in the study:

Inclusion Criteria:

• Age: 20-40 years;
• Body Mass Index: 15-30 kg/m²;
• Physical activity level (Saltin-Grimby): 2-4
• No previous or known musculoskeletal, neurological, rheumatic or tumoral diseases