WB-EMS Combined With Nutritional Guidance for a High-Protein Diet on Body Composition, Muscle Function, Psychological and Functional Outcomes in Older Adults With Excess Adiposity

This is a 16-week, parallel-group, outcome-assessor-blinded randomized clinical trial (RCT), approved by the UniCesumar Ethics Committee (Opinion No. 8.718.082 / CAAE: 01410126.9.0000.5539). The study aims to investigate the effects of resistance training combined with whole-body neuromuscular electrical stimulation (WB-NMES) and nutritional guidance focused on a high-protein diet on body composition, anthropometric parameters, and quality of life in older adults with overweight and obesity residing in Maringá-PR, Brazil.

The sample will consist of 36 older adults of both sexes (age $\ge$ 60 years, BMI $\ge$ 25 $kg/m^2$, and physically inactive), randomly allocated (stratified randomization by sex in a 1:1:1:1 ratio) into four experimental groups (n = 9 per group):

RT + NOR: conventional resistance training combined with normoprotein diet guidance;

RT + PRO: conventional resistance training combined with high-protein diet guidance;

WB-NMES + RT + NOR: resistance training using WB-NMES combined with normoprotein diet guidance;

WB-NMES + RT + PRO: resistance training using WB-NMES combined with high-protein diet guidance.

Training Protocol and Electrical Stimulation: The exercise interventions will take place twice a week (sessions of approximately 25 minutes) over 16 weeks, under the supervision of qualified professionals. Participants will perform seven exercises (leg curl, leg extension, kettlebell squat, lat pulldown, seated machine row, incline bench press, and crunch on a bench), executing 2 sets of 1 minute per exercise, with a 45-second rest interval. Training intensity will be progressive and monitored by the OMNI Rating of Perceived Exertion Scale (OMNI-RPE: 2-3 in Phase 1 up to 7-8 in Phase 4, with a gradual load reduction phase in the 16th week).

In the WB-NMES groups, the exercise will be simultaneously combined with electrical current applied through a suit with integrated electrodes (frequency of 85 Hz, pulse width of 400 $\mu$s, duty cycle of 5 s on/5 s off, and a ramp-up time of 0 s). Intensity adjustments will be limited to a maximum of 5 points on the Visual Analog Scale for pain/discomfort (VAS 0-10). All participants will undergo prior familiarization sessions.

Nutritional Intervention: This will be conducted through a hybrid approach (individualized face-to-face sessions and remote monitoring via a WhatsApp group), prioritizing contextualized nutritional education. In the high-protein intake groups, the consumption goal will be 1.2 to 1.5 g of protein/kg/day, distributed evenly across meals. In the normoprotein (control) groups, the guidance will focus on general principles of healthy eating and hydration, without encouraging an increase in protein intake.

Assessments and Outcomes: Assessments will be performed at baseline (T0) and after 16 weeks (T16).

Body Composition: Assessed using multi-frequency bioelectrical impedance analysis (InBody 570) under a strict preparation protocol (lean mass, skeletal muscle mass, total and visceral body fat, body water), with reproducibility verified on two distinct days at T0.

Anthropometry: Circumferences (neck, waist, abdomen, hip, thigh, and calf) measured in duplicate by a blinded evaluator, following ISAK guidelines.

Physical and Functional Performance Assessment:

Maximal Isometric Strength (Upper Limbs): Assessed by handgrip dynamometry (Jamar®), following ASHT guidelines. The participant will perform three attempts with each hand, sitting in a standardized posture, with a 60-second rest interval. The highest value (kgf) of the dominant hand will be considered for analysis.

Localized Muscular Endurance (Senior Fitness Test):

Lower Limbs: 30-second chair stand test (maximum full repetitions in a standardized chair).

Upper Limbs: 30-second arm curl test. Using a 2 kg (women) and 4 kg (men) dumbbell, the maximum number of correct repetitions with the dominant arm will be recorded.

Muscular Power (Upper Limbs): Medicine ball throw (2 kg). The participant, seated and without feet touching the floor, will throw the ball forward explosively. Three attempts will be made (60s interval), considering the longest distance achieved.

Aerobic Endurance: 6-minute walk test (6MWT) in a 30-meter corridor, following ATS guidelines. The total distance will be recorded, along with heart rate monitoring and perceived exertion (Borg Scale) pre- and post-test.

Functional Mobility and Fall Risk: Timed Up and Go (TUG) test. Will evaluate the time (in seconds) taken to rise from a chair, walk 3 meters, return, and sit down. Two attempts will be performed, considering the shortest time.

Self-Reported Functional Capacity: Self-reported functional disability will be measured with the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) (36-item version), developed by the WHO, assessing difficulties in the last 30 days across six domains. Responses range on a five-point Likert scale, and the scores, calculated by simple sum, are converted to a 0 to 100 scale, where higher scores reflect greater disability. The instrument will be applied self-administered or by interview to complement objective physical data with the participants' own perception of the impact of each intervention.

Psychosocial, Motivational, and Adherence Assessments:

Basic Psychological Needs: Satisfaction in the exercise context will be assessed by the Brazilian version of the Basic Psychological Needs in Exercise Scale (BPNES) (12 items, 5-point Likert scale). The instrument covers three subscales: Autonomy, Competence, and Relatedness. Higher mean scores indicate greater satisfaction of the respective psychological need.

Motivational Regulation: Will be measured by the Brazilian version of the Behavioral Regulation in Exercise Questionnaire (BREQ-3) (23 items, 5-point Likert scale), which assesses six forms of behavioral regulation (from amotivation to intrinsic motivation). From the results, the Relative Autonomy Index (RAI) will be calculated, in which more positive values reflect a more autonomous motivational profile.

Program Adherence: Quantified by the participants' relative attendance at supervised sessions (sessions attended / scheduled sessions $\times$ 100%), with a minimum target set at 75%.

Quality of Life: Assessed using the World Health Organization Quality of Life - Old (WHOQOL-OLD) questionnaire, developed by the WHO specifically for older adults. The instrument consists of 24 questions (5-point Likert scale) distributed across six facets: Sensory Abilities; Autonomy; Past, Present and Future Activities; Social Participation; Death and Dying; and Intimacy. The questionnaire will be applied individually by trained researchers. Scores will be converted to a standardized 0 to 100 scale, where higher scores indicate a better perception of quality of life.

Statistical Analysis: Analyses will follow the intention-to-treat (ITT) principle, using Linear Mixed Models for Repeated Measures (fixed factors: Group and Time; random factor: Participants), followed by Tukey's post-hoc test (significance level set at $p < 0.05$).