Resistance Exercise Program in Cognitively Normal Older Adults: CERT-Based Exercise Protocol of the AGUEDA Randomized Controlled Trial

The total prescribed volume of the AGUEDA trial for each participant assigned to receive exercise was 24 weeks with 3 sessions per week of 60 min duration. Therefore, each participant was prescribed a total of 72 training sessions. The volume is measured by; (i) number of sets (i.e., 3), (ii) number of repetitions (i.e., as many as possible) and (iii) time of set execution (i.e., from 40 to 60 seconds).

Intensity was measured primary by the 10-point Borg Rating of Perceived Exertion scale (RPE) with a target rating of 7–8 (i.e., Very difficult) (48). The Thera-Band RPE scale (47) was also used during the familiarization weeks (i.e., 2 first weeks) to help participants learn the use of the RPE scale with elastics bands. The modifiable variables used to control the intensity were (i) velocity of execution (i.e., as fast as possible), (ii) rest (i.e., 60 seconds of rest each set) and, (iii) levels: basic (level 1), intermediate (level 2) and advanced (level 3). These different levels (8 weeks per level), including 3 training sessions per week/level, progressively increased across the motor complexity of exercises and elastic band resistance (Table 1). Motor complexity involves increasing technical difficulty level of the exercise, which raises the demand for other physical abilities during the resistance exercise stimulating multi-systemic (or multi-component) adaptations (coordination, balance, core stability, power, agility, among others) (49). These multi-systemic adjustments are due to the different characteristics of the resistance exercises: (i) unilateral execution of exercises, which increases the coordination level, and provide changes in the activation pattern of trunk stabilizer muscles (e.g., unilateral push press) (46), (ii) performance of exercises with non-cyclical patterns of movement (e.g., Turkish get-up), which elevates the level of coordination and improves motor control, (iii) multi-segmental exercises that raise the level of stress on the neuromuscular and motor control system (e.g., woodcutter rotation) promoting continuous adaptations (45) or (iv) instability exercise, demanding for balance, joint, and core stability (e.g., walking lunge) (49).

Furthermore, increasing the motor complexity of resistance training exercises in older populations enhances functional capacity, which can transfer daily activities and independence (49).

A summary of the type and load is presented in Figure 2. However, the total dose was quantified on an individualized and standardized basis as explained below.

Participants were prescribed 3 sets of 8 exercises per session. The duration of each set was from 40 to 60 seconds according to each week’s assigned level with a rest of 60 seconds between sets. The resting time between exercises was adjusted to the instructions and preparation to the next exercise. The execution time equally increased at each level to ensure that each participant achieved the targeted intensity with a proper technique: 40 seconds per set execution within the first 3 weeks, 50 seconds of execution within the next 3 weeks and 60 seconds of execution within the 7th and 8th week. This equal number of sets and time allowed each participant to perform a certain number of repetitions according to their own capabilities. Velocity of the different exercises was used as another measure to modulate the intensity and adaptations at a muscular level, using as fast as possible but controlled execution speed (i.e., 1 sec of eccentric and 1 sec of concentric phase) (50). In addition, the maximum prescribed-target intensity was 70–80% of the participants’ maximum rating of perceived exertion (7–8 RPE). RPE was recorded after each exercise and at the end of the entire session (47) (File A1). Participants started the exercise program within 2 weeks of familiarization. The familiarization period focused on exercise techniques described above using controlled execution speed and not on intensity (i.e., 2 sec of eccentric and 2 sec of concentric phase).

It was important to consider the individual limitations and physical differences among participants to achieve the desired intensity, particularly in older populations. All participants started the exercise program with a soft elastic resistance (e.g., yellow-soft) for familiarization with the different exercises, but the resistance on the elastic bands increased on an individual basis. Elastic resistance was progressively increased at the judgement of the trainer and participant, aiming to reach the weekly target RPE, based on the standardized basis mentioned above.

The warm-up lasted ∼8 min and included: (i) myofascial massage with foam roller or tennis ball, (ii) joint mobility (i.e., thoracic, shoulder, knee and hip mobility), and (iii) cardiovascular game (e.g., relay race).

The duration of the main exercise intervention lasted about 45 min. There were 3 different exercise sessions per level, and each exercise session included 8 different exercises. The exercise progression from one exercise to another was done sequentially (i.e., 3 sets of exercise 1 – rest – 3 sets of exercise 2). Table 1 describes the exercises included in each exercise session and each level. The selected exercises included basic movement patterns (51) involving large muscle groups, horizontal traction, vertical traction, horizontal thrust, vertical thrust, hip extension and flexion, hip dominants, knee dominants, anti-rotation, anti-extension, anti-flexion, and antilateral flexion (52). Each session start with exercises in standing position (i.e., except training session 1 of level 3 that began with push-ups) and ended with specific lumbopelvic exercises in prone or supine position to avoid abrupt changes in body position that may cause dizzinesss (53).

The cool-down lasted approximately 7 min. This phase aimed for relaxation including myofascial release (54), joint mobility or stretching (i.e., static, or dynamic), and was focused on the trained muscle groups.

Exercise adaptation is an important factor when designing exercise programs, particularly in older adults (53, 55, 56). The AGUEDA exercise program included specific adaptations for the exercises due to different causes:

The retention was calculated from the number of participants from the intervention group who had completed the post assessments (65). Study retention was 95.65% (44 of 46 participants completed the post assessments).

Adherence to the exercise program was measured by session attendance by the proportion of sessions completed out of the total prescribed sessions. An 80% attendance was required for the per protocol analysis (i.e., > 57 exercise sessions). Exercise sessions were performed on a regular basis during holidays (i.e., summer or Christmas). Any missed session was registered and rescheduled to an alternative date to maximize program adherence. For exceptional cases when rescheduling was not feasible, online sessions were conducted through a video call using the following materials: (i) mobile phone, (ii) Polar band H10, (iii) elastics bands, (iv) RPE scale, and (v) an online training program guide previously explained in detail (File A8).

The average recorded attendance of 46 participants was 84.12%. 10% (53 out of 454 sessions) of the missed sessions were rescheduled, increasing the average attendance to 85.71%. 2 participants had less than 60% of attendance, 3 participants between 60–80%, and 41 participants achieve >80%. External factors to the exercise program were identified as the cause for missed sessions. Reasons for the lowest adherence (<60% of attendance) were unwillingness to undertake the exercise program for the presence of a health condition. Regarding the others, the 3 participants missed sessions due to health conditions.

In addition, specific strategies were implemented to promote participant engagement:

Upon program completion, three additional strategies were used to help participants to continue engaging in exercise:

Any adverse event that occurred, such as injury, emergency, or scheduled surgery, was recorded, reported, and evaluated by the research team in REDCap (68), an online platform designed to store and manage electronic data. Adverse data were recorded, if possible, at the time of the event but also asked at midpoint and post assessments (i.e., at 12 and 25 week) by a phone call. A customized adverse event form (File A7) included the seriousness, severity, chronicity, and resolution occurrence in participants, even events unrelated to the exercise program (e.g., COVID). The severity of adverse events was classified in 3 categories (i.e., mild, moderate, severe) (69). In case of joint injury or other injuries, a physician clearance was required before rejoining the resistance exercise program. There was 1 severe adverse event during the intervention period but without causal relationship with assessments or the exercise program.

We report an estimation of the cost of delivering the AGUEDA exercise program including the human resources and equipment (Table S5). The cost is based on an average group size of 6 participants. The estimated total cost of the 24-week AGUEDA resistance training program was 6623.58 €, with an approximate cost of 144.23 € per participant and 865.49 € per group.

The costs have been calculated in based to the minimal material required for replication in any context. Benefits of body weight resistance training has been recognized by the ACSM by a functional way to exercise with minimal equipment and space, making it an inexpensive, convenient, and accessible form of exercise for people of all ages and fitness levels (70).

Equally the use of elastic bands is increasing as an alternative method for improve muscle strength (71, 72) in older adults because of the following reasons: (i) low-cost and available instead of weight machines (73–75), (ii) convenient to different levels of physical fitness (76) and (iii) portability; allowing individuals home or outdoor use (75).