In relation to the 2 groups that will perform HIIT, the HIIT+AF will have to complete 10.000 steps per day. In this way, they will be focusing on increasing their daily physical activity. In addition, this group will perform the same HIIT training programme as the other experimental group.

This group will not suffer any changes in their lifestyle

Maximum oxygen consumption (VO2max) will be estimated from the maximum power output (MPO) achieved in an incremental cycloergometer test (Andersen, 1995). Therefore, only the MPO will be taken into account for its estimation, since it is a measure of the capacity of the cardiorespiratory system, which can predict 80% of the variation in VO2max.

The development of the test begins with a first part of 7 minutes at a submaximal load of 69W. At the end of this phase the heart rate was recorded with a pulsometer (H10 Polar Electro OY, Finalandia). The load will be increased by 35W every 2 minutes until the subject reached exhaustion.

Physical activity will be evaluated objectively by accelerometry. The accelerometer is a device that allows objective quantification of the physical activity performed by a person. The study population was asked to wear a triaxial accelerometer (GTX3, Penascola, Florida, USA).

Participants were instructed to wear the accelerometer throughout the day (24h). The placement of the accelerometer during the recording days should be on the right side at hip height and in line with the anterior face of the ipsilateral lower extremity. To avoid damage to the device, it was removed in any aquatic situation. On this occasion, a record sheet was provided for its annotation.

To detect changes in health-related quality of life, the SF-36 questionnaire will be used. This questionnaire, in its Spanish versión (Vilagut et al., 2005), focuses on assessing general health status through a generic scale. This provides a profile of quality of life, both of a general population and of specific subgroups.

This questionnaire consists of a total of 36 questions covering 8 health concepts. In addition, there are two summary measures, which are physical health and mental health. Mental health is divided into the vitality scale (4 items), social functioning (2), emotional role (3) and mental health (5). On the other hand, physical health encompasses physical capacity (10 items), physical role (4), bodily pain (2) and general health (5). In addition, two global questions on the perception of their health are added.

The scores for each scale range from 0 to 100, with higher scores indicating a better quality of life

The Rosenberg self-esteem scale (1965) is the most widely used test for the evaluation of self-esteem in scientific research and clinical practice.

This test is a 10-item scale for analyzing global self-esteem (Vázquez Morejón et al., 2004). Each item is classified on a 4-point Likert scale, where 1 is equivalent to "strongly disagree" and 4 to "strongly agree". Of the 10 questions asked, five are formulated positively and five negatively (2,5,8,9,10). In addition, each question measures the degree of satisfaction of the person together with the person's self-assessment.

In relation to the results, the unifactorial nature proposed by Rosenberg has been questioned; however, other authors support a bifactorial structure of positive and negative self-esteem. According to the validation study of this work in Spanish (Atienza et al., 2000), when the sample is made up of women, the elaboration of a single factor of global self-esteem is suggested.

The HDRS (Hamilton, 1960) is a scale for assessing depression. It is hetero-applicable and is designed with the aim of quantitatively assessing the degree of depression of the interviewed subject.

The original version consists of 21 questions, but on this occasion the reduced versión (Hamilton, 1967) published later will be used. This version consists of 17 questions, which is recommended for clinical use.

The short version of the HDRS has been validated in the Spanish version (Ramos-Brieva & Cordero Villafáfila, 1986) showing high reliability and sensitivity to change in different populations (Ramos-Brieva & Cordero-Villafafila, 1988).

The measurements of the following cognitive tests will be performed with the collaboration of a psychologist specialized in the execution and description of the following executive tests:

For the evaluation of inhibitory control, the Stroop testT will be used (Golden, 1999). This is a neuropsychological test that measures the interference generated in the performance of a task. In this work, the Victoria version will be developed in a digitized form (Mueller et al., 2012).

For the evaluation of cognitive flexibility, wil be used the Wisconsin card test (WCST) (Cepeda et al., 2000). It can be performed traditionally or, as in this case, digitally. This test consists of a total of 64 cards. The cards present different combinations according to 4 geometric shapes, 4 colors and 4 quantities.

Digit Span Test (DST) analyzes the ability to store and retain information, whose mission is to measure working memory.

Leg extension muscle strength will be assessed on a calibrated isokinetic dynamometer (Biodex System 4, Biodex Medical System, Inc., Shirley, NY, USA). Therefore, the Biodex System 4 will be used to assess each subject's ability to generate maximal isometric power with the knee extensor musculature in a 60° flexion joint position from a seated position.

For measurement, the Biodex clinical data station will be used to analyze the Biodex torque and position signals and obtain the resulting measurements.

The performance protocol will consist of executing two maximal isometric efforts for 5 seconds. The subject, with arms crossed over the chest, will begin to perform the maximal force at the evaluator's "push" voice. Subsequently, the subject will rest 30 seconds to perform the second attempt.

Once both attempts have been completed, the best result of the peak torque variable (N-M) will be recorded for further analysis.

Upper extremity muscle strength will be assessed through manual dynamometry testing with a digital dynamometer (TKK 5101 Grip-D; Takey, Tokyo, Japan) as described in other studies (Ruiz-Ruiz et al., 2002).

Subjects were to be placed in a bipedal position during the test with the arms in full extension and without touching any part of the body with the dynamometer, except for the hand. The positioning of the body should be at all times with the shoulder girdle parallel to the ground, without allowing flexion or lateral movement of the trunk during the application of force.

The participants will be instructed to squeeze the dynamometer grip as hard as possible and without being able to bend any of the joints involved. The duration of the effort will be 5 seconds, without being able to perform discontinuous activations, i.e., they must maintain the maximum isometric force possible during the 5 seconds.

Finally, the best result (Kg) of the two tests performed will be recorded.

The Beck-II (Beck & Steer, 1993) is used to measure depressive symptomatology.

It is a self-administered instrument consisting of 21 items that assess cognitive, affective and neurovegetative factors. This questionnaire is usually the most widely used in clinical psychology to assess the degree of depression (Sanz et al., 2003).

This questionnaire has been validated in the Spanish version (Sanz et al., 2005) and has also shown high reliability in a university population (Sprinkle et al., 2002).

Each item has four responses, ordered from least to most severe (from 0 to 3 points), and the subject must choose the sentence that most closely matches his or her perception during the last week. The scores of this instrument range from 0-63, with the reference cut-off points being the following: 0-9 no depression; 10-15 mild depression; 16-19 moderate depression; 20-29 moderate-severe depression; 30-63 severe depression.

The IPAQ questionnaire is an instrument to determine approximately the level of physical activity practiced by the general population (Hagstro et al., 2006). This questionnaire is one of the most widely used for the detection of sedentary lifestyles, used to a greater extent in its short version, adapted and translated into Spanish. In addition, this questionnaire shows excellent reliability (Craig et al., 2003) and high validity for its application in university population (Cancela et al., 2019).

Therefore, for the calculation of the IPAQ data, an average of Mets will be adopted for each type of activity, resulting as follows: walking 3.3 Mets, moderate activities 4.0 Mets and intense activities 8.0 Mets.