2.2. Interventions

The clinical trial consists of two interventions: (1) supplementation with S. maxima (5 g/day) or placebo (5 g/day of a low-calorie saccharine), and (2) an exercise program, during a period of 24 weeks in a randomized, double-blind, counterbalanced, crossover, controlled trial with a 2 × 2 factorial design. Presentation of both supplements will be powder encapsulated in dark capsules of 0.5 g to present the same organoleptic attributes and mask their individual characteristics.

Inclusion in the exercise program intervention will be decided by each participant, who will be randomly assigned to one of the two possible nutritional interventions (S. maxima or placebo) categorized into four treatments: an exercise program plus S. maxima intake; exercise with placebo administration; S. maxima intake without exercise, or placebo supplementation without exercise program (Control). To assess compliance to the supplement intake, a crossover will be conducted for the supplementation interventions.

The first period of treatment will be carried out for 12 weeks, followed by a four-week wash-out period to avoid any possible delayed effect of S. maxima in the organism. Finally, a further 12 weeks of treatment for the second intervention groups (Figure 1).

Flow diagram of the experimental design for the impact of Spirulina maxima intake and exercise (SIE) trial. Same color indicates the same group of participants.

Due to absence of data related to wash-out and treatment periods length, we considered 4 and 12 weeks, respectively, as stated by a systematic review of clinical trials that used spirulina as treatment [22].

Participants in the exercise program groups will exercise five days a week. The physical activity program will be conducted in accordance with the American College of Sports Medicine recommendations [23] and will consist of Monday to Friday chair exercises performed during 24 weeks.

The approximate exercise duration will be of 40–50 min. Each exercise session has an initial or warm-up phase of 5–10 min (joint movement exercises to increase body temperature starting with movements of head, upper extremities trunk, hip, and, lower extremities); a main physical conditioning phase of 25–30 min that will consist of developing a personalized circuit of strength exercises of the main muscle groups (arms, shoulder, chest, back, and legs) at moderate intensity (between 3.0 and 6.0 metabolic equivalents of task (METs)) using rating of perceived exertion scale and the Talk Test; finally, a cool-down or relaxation phase of 5–10 min. To define the individual exercise intensities in the main physical conditioning phase, participants will have a training of 3 to 5 days before the beginning of the clinical trial to learn how to use the rating of perceived exertion scale and the Talk Test as markers of exercise training intensity.

Trained personnel will assist older adults to perform the exercise program, including articular flexibility, postural exercises, and proprioception exercises. These activities will be selected according to the individual deterioration and joint stiffness that the participants could present. Researchers are trained in cardiopulmonary resuscitation and the laboratory has the necessary tools and communication channels to carry out emergency procedures if a participant presents any side effect of exercise.

Participants will visit the laboratory weekly to receive new supplements and related information, which will be registered on case report formats. Treatment adherence will be assessed by counting the remaining capsules when the participants return to the laboratory. Participants will be asked to report as soon as an adverse effect occurs to analyze the possibility of suspending supplementation.