Mejora de la Reserva Física para Promover la Resiliencia en Adultos Mayores Físicamente Frágiles (MRI exercise)

Participants will complete two aerobic training sessions and two resistance training sessions per week for a total of four exercise training sessions each week lasting for 3-month (i.e., 13-weeks). Aerobic exercise intensity will be tracked through heart-rate monitors with an age-specific targeted heart-rate-reserve initially set at 50% and progressively increased by 5% weekly until 70% heart-rate-reserve is reached in Week-5, then it will be sustained for the remainder of the trial. The first four weeks of the resistance training program will emphasize on assisting the study participants in gaining familiarity with proper technique. The intensity of the resistance training stimulus will be set to a weight where the participants can complete two sets of 10-15 repetitions, then progressed from 45% to 85% of predicted 1-repetition-maximum determined at Week-4 using the 8-rep maximum test. The 8-rep maximum test is rrepeated every 4 weeks to ensure the exercise intensity is maintained

The aerobic training sessions will involve standardized sets of stationary training, including on-spot jogging, burpees, aerobic steppers, agility ladders, and non-contact boxing. Each participant will rotate through the stations within the 40-minute training period, with one-minute of rest breaks in-between each station. A 20-point rate-of-perceived exertion will be used to monitor participant status during training with a target rate-of-perceived exertion of 16-17.

The resistance training sessions will involve utilizing free weights and resistance bands to stimulate muscle strength. The set of movements include triceps extension, dumbbell bicep curls, seated overhead dumbbell press, bent-over dumbbell row, wall squats, standing calf raises, wall push-ups.

Participant Retention and Care: Investigator will implement strategies to promote participant retention by: (1) conducting monthly phone calls by the project assistant to encourage and motivate participants to stay within the study; (2) discussing participant barriers/distress and developing coping/action plans; (3) providing monthly updates in the form of in-person/online/phone sessions; and (4) offering a comprehensive report on cognitive function, mobility, brain MRI, and monetary compensation for their time upon completion of the study.

Investigator will facilitate participant care by recording incidental findings from the MRI and providing clinical assessment data that may be shared with healthcare providers upon request. All personnel on the research team will be trained to detect/assess distress or any possibility of harm and respond appropriately.

Participant Retention and Care: Investigator will implement strategies to promote participant retention by: (1) conducting monthly phone calls by the project assistant to encourage and motivate participants to stay within the study; (2) discussing participant barriers/distress and developing coping/action plans; (3) providing monthly updates in the form of in-person/online/phone sessions; and (4) offering a comprehensive report on cognitive function, mobility, brain MRI, and monetary compensation for their time upon completion of the study.

Investigator will facilitate participant care by recording incidental findings from the MRI and providing clinical assessment data that may be shared with healthcare providers upon request. All personnel on the research team will be trained to detect/assess distress or any possibility of harm and respond appropriately.

Mobility

Physical reserve will be operationally defined as the unexplained residual variance in 30-second Sit-to-Stand Test after accounting for the effects of age, cognitive capacity, and brain structural integrity.

Cognitive capacity will be assessed by the Alzheimer's Disease Assessment Scale-Cognitive-13. It measures memory, language, praxis, attention, and executive function, with scores ranging from 0 to 85; higher scores indicate greater cognitive impairment.

Total hippocampal volume will be selected to reflect brain structural integrity

The Trail Making Test will comprise Part A and Part B. In Part A, participants are instructed to connect numbers in sequential order (e.g., drawing a line from 1 to 2, 2 to 3, 3 to 4, etc.) while being timed. In Part B, participants are instructed to connect, in order, 25 encircled numbers and letters alternately (e.g., 1-A-2-B-3-C) while being timed. A longer time represents worse executive function.

Functional MRI will be used to measure resting state functional connectivity

Years of education of participants will be recorded

Physical activity will be assessed by the Physical Activity Scale for the Elderly. Higher scores represent better physical activity.

Body mass index will be calculated as weight in kilograms divided by height in meters squared (kg/m²).

Physical frailty will be assessed by the Pictorial Fit-Frail Scale. It involves 14 domains, with scores ranging from 0 to 43; higher scores indicate severely frail.

Physical frailty will be measured by the Short Physical Performance Battery. It measures balance, walking, and sit to stand, with scores ranging from 0 to 12; higher scores indicate greater mobility.

General cognitive function will be assessed by the Montreal Cognitive Assessment. It measures memory, language, visuospatial, attention, and abstract reasoning, with scores ranging from 0 to 30; higher scores indicate greater general cognition.

Total number of comorbid conditions will be assessed through the Functional Comorbidity Index , with a maximum score of 18. A lower score indicates fewer comorbidities.

Sleep duration will be recorded in hours over the last 24 hours and the last 7 days.