Participants will carry out an online synchronic supervised physical exercise intervention through their computer/tablet or mobile phone at home. The exercise professional will supervise the participant's execution online and will also apply motivational strategies based on self-determination theory. The training program comprises the same exercise structure and is based on the same muscle groups and movements as the supervised face to face groups. The exercise program will be divided into 3 different levels, progressing the difficulty every 8 weeks. Each level will contain 3 different sessions including 10 warm-up and joint mobility exercises, 1 balance exercise, 7 strength exercises, 2 aerobic exercises, and 6 flexibility exercises. This multicomponent training will be performed 3 times per week (60 min/session) for 24 weeks.

Participants will attend the sports facilities and perform the training in small groups, being supervised by an exercise professional. The training program comprises the same exercise structure and is based on the same muscle groups and movements as the online synchronic supervised groups, but is performed in a sports center. The exercise program will be divided into 3 different levels, progressing the difficulty every 8 weeks. Each level will contain 3 different sessions including 10 warm-up and joint mobility exercises, 1 balance exercise, 7 strength exercises, 2 aerobic exercises and 6 flexibility exercises. This multicomponent training will be performed 3 times per week (60 min/session) for 24 weeks.

Participants will attend the sports facilities and perform the training in small groups, being supervised by an exercise professional who will also apply motivational strategies. The training program comprises the same exercise structure and is based on the same muscle groups and movements as the online synchronic supervised groups, but is performed in a sports center.

The exercise program will be divided into 3 different levels, progressing the difficulty every 8 weeks. Each level will contain 3 different sessions including 10 warm-up and joint mobility exercises, 1 balance exercise, 7 strength exercises, 2 aerobic exercises and 6 flexibility exercises. This multicomponent training will be performed 3 times per week (60 min/session) for 24 weeks.

Maximum gait speed will be evaluated by measuring the time used to walk 3, 4, 6 and 10 meters linear distance at maximum pace without running. Gait speed is calculated by dividing the distance into registered walking time. A higher speed (or lower registered time) better performance.

Usual gait speed will be evaluated by measuring the time used to walk 3, 6 and 10 meters linear distance at usual pace. Gait speed is calculated by dividing the distance into registered walking time. A higher speed (or lower registered time) better performance.

It consists of three parts: the ability to stand with feet together in side-to-side, semi-tandem, and tandem positions (balance), 4-meters walk test (speed), and 5 times sit-to-stand (muscle power). Each part is scored from 0 to 4, with a total SPPB score of 12 points, a higher score, better performance.

SFT battery includes 30-second chair stand test (lower-body strength), 30-second arm curl test (upper-body strength), 6-minute walk test (aerobic endurance), Chair sit-and-reach test (lower-body flexibility), Back scratch test (upper-body flexibility) and 8-foot up-and-go test (agility and dynamic balance).

Systolic and diastolic blood pressure will be assessed in a seated position, twice, 2 minutes apart, after 5 minutes at rest, using a digital upper arm blood pressure monitor (OMRON M6, Spain). Blood pressure will be assessed at the level of the right atrium, with the participant's back supported and uncrossed legs with both feet on the floor.

Heart rate will be assessed in a seated position twice, 2 minutes apart, after 5 minutes at rest, units will be bpm (beats per minute), using a digital upper arm blood pressure monitor (OMRON M6, Spain).

Height will be measured with a stadiometer (Seca 213, Hamburg, Germany). Body mass will be measured using a body composition analyzer (InBody 770, Biospace, California, USA). The participant will be barefoot and wearing as minimally clothed as possible.

Body mass index will be calculated as body mass (kg) divided by height (m) squared (kg·m-2).

Waist and hip perimeters will be measured in upright position in accordance with the ISAK guidelines with a circumference tape (Lukfin, W606PM) following the standardized protocol, as well as calf perimeter in a sitting position.

Body Composition will be measured using a body composition analyzer (InBody 770, Biospace, California, USA), following the standardized protocol. Fat mass (kg and %), fat free mass (kg and %) and skeletal muscle mass (kg and %) will be obtained.

The EuroQol-5D questionnaire will be used for assessing the health-related quality of live of the participants, including five dimensions and a visual analogue scale. The 5 dimensions included in the descriptive system are (1) mobility, (2) self-care, (3) usual activities, (4) pain/discomfort, and (5) anxiety/depression. Responses will be coded according to the three-level scale for each dimension. A utility value will be assigned to each combination of responses. This index provides a quantitative measure of each individual's health-related quality of life, where 0 represents the worst possible health and 1 represents the best possible health.The EQ-VAS scale consists of asking participants to indicate their current health status from 0 ("worst imaginable health status") to 100 ("best imaginable health status").

The Montreal Cognitive Assessment (MoCA) assesses different cognitive domains: attention and concentration, executive functions, memory, language, visuoconstructional skills, conceptual thinking, calculations, and orientation. The total possible score ranged from 0 to 30, and the highest score indicates better performance.

The Stroop Color and Word Test (SCWT) is divided into three conditions, the first condition consists of reading color names printed in black ink, in the second condition the participant will read colors printed in an "X", and the third condition consists of naming the ink color instead of reading the word. All conditions contain 100 words, and time is limited to 45 seconds for each condition. The total number of correct words for each condition will be recorded, indicating that the higher the number of correct words, the better the performance.

Digit Span test of the Wechsler Adult Intelligence Scale III (WAIS III). Participants will be asked to recall a list of numbers in the order given (forward or backwards). The test is finished when for the same item, the participant fails two attempts. A total number of correct answers will be registered for each condition, ranging from 0 to 30, with the highest scores being the best performance.

The test consists of drawing a clock with a given time (11:10). The total score is the sum of the scores given to dial, numbers and clock faces, ranging from 0 to 10 with the highest scores being the best performance.

Digit Symbol Substitution Test. The participant will fill in a series of coded symbols for 90 and 120 seconds. The total number of responses as well as errors are recorded. In this test, the higher the score, the better the performance.

The Zung Anxiety Self-Assessment Scale will be used to assess anxiety symptoms. It consists of 20 items with a 4-point response scale ranging from 1 (not at all or hardly ever) to 4 (most or all of the time), obtaining a maximum score of 80. The higher the score, the higher anxiety.

Physical activity and sedentary behavior will be assessed by accelerometry ((Actigraph GT3X, MTI, USA). The devices will be placed on the subject's non-dominant wrist using a watch strap for 8 days.

Physical activity and sedentary behavior will be assessed by the International Physical Activity Questionnaire-Short form (IPAQ). This questionnaire ask about the time spent on vigorous, moderate, walking and sitting activities in the last 7 days.

The number of hours of sleep will be assessed by accelerometry ((Actigraph GT3X, MTI, USA). The devices will be placed on the subject's non-dominant wrist using a watch strap for 8 days.

The Pittsburgh Sleep Quality Index consists of 19 self-assessed questions and 5 partner-assessed questions. The 19 items are combined to form seven component scores (subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction), each with a range of 0 to 3 points. The total score ranges from 0 to 21, where 0 points represents no difficulties and 21 points represents severe difficulties and worse sleep quality.

Blood samples will be collected in the morning after an overnight fast and at least 24 h after the last exercise session. After collection, tubes will be centrifuged at 3500 rpm for 10 min. Serum obtained for each participant will be stored in aliquots at -80 °C until analysis. Serum BDNF (ng/mL) will be quantified using a sandwich enzyme-linked immunosorbent assay (ELISA). Human BDNF Quantikine Immunoassay (R&D Systems, Minneapolis, MN) will be performed according to the manufacturer's instructions.

Blood samples will be collected in the morning after an overnight fast and at least 24 h after the last exercise session. After collection, tubes will be centrifuged at 3500 rpm for 10 min. Serum obtained for each participant will be stored in aliquots at -80 °C until analysis. A commercial enzyme-linked immunosorbent assay (ELISA) will be performed to measure α-klotho serum concentration (pg/ml) according to the manufacturer's protocol (Human soluble α-Klotho Assay Kit JP27998, Immuno-Biological Laboratories Co., Ltd., Gunma, Japan). The quantification will be performed spectrophotometrically using a FLUOstar OPTIMA Microplate Reader (ThermoFisher Scientific, Waltham, MA, USA) and Optima Control software version 2.20.

Glucose, uric acid, urea, creatinine, bilirubin, sodium, potassium, chloride, calcium, phosphorus, total proteins, albumin, cholesterol, cholesterol-HDL, cholesterol-LDL (calculated), triglycerides, aspartate transaminase (AST), alanine transaminase (ALT), gamma-glutamyltransferase (GGT),alkaline phosphatase, lactate dehydrogenase (LDH), creatine kinase (CK,) will be measured using routinary clinical techniques.

It consists of the analysis following parameters: red blood cell count, hemoglobin concentration, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, red cell distribution width, white blood cell count, differential white blood cell count, platelet count and mean platelet volume

Motivators and barriers to exercise will be measured using the Exercise Benefits/Barriers Scale. It is a 43-item instrument with a four-response Likert-type scale; Twenty-nine items are related to the benefits, while the remaining 14 are barriers. - The total score of the instrument can range from 43 to 172 points, with higher scores indicating a more positive perception of exercise.

The Behavioral Regulation during Exercise Questionnaire (BREQ-3) comprises 23 items (4 for intrinsic regulation, 4 for integrated regulation, 3 for identified regulation, 4 for introjected regulation, 4 for external regulation and 4 for amotivation) that measure the stages of the self-determination theory with respect to motivation to exercise. Participants will answer each item on a 5-point scale ranging from 0 (not true for me) to 4 (very true for me). Higher scores on identified regulation, integrated regulation and intrinsic motivation are generally considered indicative of a more self-determined and healthy motivation towards exercise. On the other hand, higher scores on amotivation, external regulation and introjected regulation generally indicate less self-determined motivation.

The Basic Psychological Needs in Exercise Scale (BPNES) is composed of 12 items assessing the satisfaction of the three basic psychological needs in physical exercise contexts: competence, autonomy and relationship with others. A 5-point likert scale is used: (1) Do not agree at all, (2) Somewhat agree, (3) Somewhat agree, (4) Strongly agree, and (5) Strongly agree.using : (1) I don't agree at all, (2) I agree a little bit, (3) I somewhat agree, (4) I agree a lot, and (5) I completely agree. For each need, a minimum score of 4 points and a maximum of 20 points can be obtained. The score for the total questionnaire would be a minimum of 12 points and a maximum of 60 points. A higher score reflects a better satisfaction of basic psychological needs.

The Satisfaction with Life Scale is a 5-item instrument with a Likert-type scale ranging from 1 to 5 points, and measures overall subjective happiness through statements in which participants rate themselves. The higher the score, the higher the satisfaction with life.

Age, sex, marital status, educational level, socioeconomic status, employment status, self-rated health, family history of Alzheimer, pathologies diagnosed, number of falls during the previous year, consumption of medicines, and tobacco and alcohol consumption will be determined by this questionnaire

A cost-effectiveness analysis will be performed to assess the expenses associated with each intervention group, utilizing the EQ-5D questionnaire to evaluate changes in health states.The analysis will focus on the following key metrics, the Quality-Adjusted Life-Year (QALY) and the Incremental Cost-Effectiveness Ratio (ICER).

The Cost-Utility analysis examines an intervention's cost-effectiveness by considering expenses and the impact on patients' quality of life. QALYs provide a comprehensive measure of both the quantity and quality of life, calculated by multiplying the utility weights assigned to each health state by the time spent in that state. The cost per QALY gained is determined by dividing the total intervention costs by the total QALYs gained.

The ICER compares the cost-effectiveness of two interventions by evaluating the difference in costs and effects (QALYs gained). A positive ICER indicates that Intervention A is more expensive and less effective than Intervention B

Adherence to physical training program will be recorded by the trainers. It will be calculated as a percentage ([sessions completed/total sessions expected] x 100), where 0 % indicates total non-adherence and 100 % indicates full adherence to the exercise intervention.

During the 24-week follow-up, the investigators will assess through an ad-hoc self-reported questionnaire whether or not participants exercised during the follow up period (24 weeks), the exercise modality performed, if the exercise was supervised center-based and/or unsupervised/supervised home-based, the number of weekly exercise sessions performed, the average time and the subjective intensity perceived (light, moderate or vigorous).

Participants in the supervised synchronous online exercise and control groups will record in a diary their falls and adverse events during and outside exercise sessions. In the supervised face to face groups, supervisors will register the incidence of falls during exercise sessions an participants will register them outside the exercise sessions using the diary.