Study Protocol: Effects of Combined Resistance Training and Dual-Task Interventions on Physical, Oculomotor, and Executive Functions in Older Adults With Mild Cognitive Impairment. A Randomized Controlled Trial

A randomized clinical trial will be conducted with two experimental groups and one control group. The target population will be older adults with mild cognitive impairment living in the communities of Arica (Chile) and Valencia (Spain). All participants must score between 10 and 25 points on the Montreal Cognitive Assessment (MoCA).

The sample size was calculated using statistical software, based on mean differences reported in prior studies on training and dual tasks in older adults. A minimum of 11 participants per group was established, adjusted for a 20% dropout rate, a significance level of 0.01, and a statistical power of 0.9.

In each city, 33 participants (men and women in a 1:1 ratio) will be recruited. Random distribution by gender will assign participants to three groups:

EGR: Resistance exercises only.

EGRD: Resistance exercises combined with dual tasks (cognitive tasks).

CG: Control group, receiving standard health care during the study and, upon completion, the best-evaluated therapeutic intervention.

Procedure The study will last 12 weeks: two weeks for baseline measurements (pre-test), eight weeks for training protocols, and two weeks for final measurements (post-test). Evaluations will include sociodemographic and health data, functional physical condition tests, executive function assessments, and saccadic and anti-saccadic eye movement measures.

Interventions will be conducted at the physiotherapy faculties of the participating universities, supervised by experienced professionals blinded to group allocation. Participants will be asked not to engage in physical exercise outside the study protocols during evaluation weeks.

Hypotheses

Primary: The combined intervention of resistance exercises and dual tasks is more effective than isolated resistance training in improving physical, executive, and oculomotor functions in older adults with mild cognitive impairment.

Secondary: The combined intervention produces greater improvements in executive function tasks (Stroop Test, Corsi Block-Tapping Test, Trail Making Test) compared to resistance training alone.

Intervention Program

The intervention will last eight weeks, with three weekly sessions (20-24 sessions total). Each resistance training session will last one hour, divided into:

Warm-up: Joint mobility and basic movements; Resistance training: Exercises with external load; Cool-down: Breathing exercises and stretching.

Exercises will target flexor and extensor groups of the elbow and knee, including bilateral leg press, unilateral knee extensions, and bilateral elbow flexion/extension. Three sets of eight repetitions will be performed for each muscle group. Training intensity will begin at 60% of one-repetition maximum (1RM) and progress to 80% by week 7, adjusted every two weeks based on new strength evaluations and perceived exertion.

The combined group (EGRD) will follow the same physical protocol, incorporating memory and arithmetic tasks during exercise execution.

Assessment Instruments

Functional physical condition: Timed Up and Go Test (TUG), Short Physical Performance Battery (SPPB), and grip strength measured with a hydraulic dynamometer.

Executive functions: Inhibitory control: Stroop Test, with three conditions (word, color, word-color); Working memory: Corsi Block-Tapping Test (CBTT), assessing visuo-spatial memory sequences; Cognitive flexibility: Trail Making Test (TMT-A and TMT-B), evaluating speed, attention, and alternation.

Oculomotor function: Electrooculography (EOG) will record saccadic and anti-saccadic movements using surface electrodes and controlled visual stimuli.

Statistical Analysis Population data will be presented as means for continuous variables and prevalence for categorical variables, with 95% confidence intervals. Inferential analyses will consider normality and homoscedasticity to determine parametric or non-parametric tests. A blinded researcher will conduct all analyses using IBM SPSS version 27.