Human aging is characterized by a progressive deterioration of multiple physiologic systems, with marked decreases in skeletal muscle mass, muscle strength, physical function and quality of life beginning in the sixth decade in life. These deleterious modifications have a significant impact upon mobility and ability to undertake daily living activities in elderly people. If we consider that, according to current projections, the proportion of the European population over 65 years will increase from 17% in 2010 to 30% in 2060 and that physical activity participation rates for older adults (>60 years) remain low, with only 16% meeting the recommendations of the American College of Sports Medicine Guidelines (11% for resistance training), we need to understand what type of training (strategy) can be the most effective for reverse physical impairments, and not only that, but which one obtains greater adherence and self-perception for contribute a healthier, active and more independent elderly population in the future.

Thus, the purpose of this study is to investigate the effects of 20-week slow-speed traditional resistance training, high-speed resistance training and multicomponent training program with variable resistance (elastic bands) on molecular, body composition, neuromuscular, physical function and quality of life variables in older adults. This research also aims to evaluate if this novel types of training intervention (using variable resistances such as elastic bands in all the training programs and measure the intensity with the OMNI-RES perceived exertion specific for older adults) is feasible in this population, through analysis of adherence, intervention fidelity and self-perception reported.

Slow-speed traditional resistance training (2-3 seconds for each concentric and eccentric phase) protocols for the elderly have involved relatively heavy loads (70-80% of maximum force) in order to increase strength and function, and has been demonstrated to be an effective strategy to improve biomarkers of health and fitness across a wide range of healthy and clinical older populations, but the results regarding the function are inconsistent in the current literature. However, several studies indicated that muscle power is a stronger predictor than strength for daily motor activities, such as fast walking, stair-climbing, and rising from a chair, and that peak muscle power was associated with functional limitations in older people. Moreover, muscle power declines earlier and at a higher rate than strength. More recently, several authors have designed high-speed resistance training programs, also calling power training or explosive-type resistance training to improve muscle power in older adults rather than strength. However, the effects of high-speed resistance training versus slow-speed traditional resistance training on functional outcomes in older adults are inconsistent, with some studies showing enhanced improvements in function, and others showing no difference in function perhaps because to the application of different training parameters, tests, functional status of the participants or the lengths of the studies. Furthermore, the effects of the high-speed training programs on others variables such as oxidative stress, bone profile or metabolic function are unknown.

On the other hand, current recommendations have recognized that a combination of aerobic activity, strength training and flexibility exercises is important for maintaining physical function in older adults. However, most studies in older individuals have examined the isolated effect of strength and endurance training programs and focused on different health-related fitness parameters. Also, due to the low rates of physical activity in older adults, especially regarding resistance training (11%), it is necessary to study the effects of other types of physical activity possibly more dynamics, like the multicomponent training. Multicomponent training is defined as a well-rounded program that includes endurance, strength, coordination, balance and flexibility exercises and is becoming increasingly popular among the older population and appears to be associated with several health benefits because has the potential to impact both cardiorespiratory and neuromuscular fitness, which both play an important role in maintaining functional fitness and quality of life.

Currently however, there is no evidence which has examined the effectiveness of high-speed resistance training and multicomponent training in older adults (>60 years) in front of slow-speed traditional training not only in respect of the physical function, but also in terms of oxidative stress, bone profile, metabolic status and quality of life. Developing an understanding of novel training strategies can ultimately provide a viable alternative to traditional modes of exercise training for a broader range of participants and increase their adherence to them.

This is a randomized clinical trial (RCT) with 4 parallel arms. The subjects will be divided in 4 groups with a randomized technique: slow-speed traditional resistance training group (TRADITIONAL), high-speed resistance training group (H-SPEED), multicomponent training group (MULTICOMPONENT) and control group (CONTROL). The subjects will be submitted to a 4-session familiarization period and then a 20-week of training program will be performed twice a week.

The TRADITIONAL group will perform 6 submaximal repetitions equivalent to 85% of the one-repetition maximum (1RM) per exercise (high intensity training sessions). The perceived exertion level on the OMNI-RES scale progressed from 6-7 (somewhat hard) in the first 4 weeks to 8-9 (hard) in the remaining 16 weeks. Control of the intensity by this method (which takes into account the grip width, band color, and number of bands) has been previously validated in young adults, middle aged adults, and older adults, and will be the first time that it will be used the validate scale for older adults in the intervention training. The number of sets per exercise progressed from 3 in the first 8 weeks to 4 in the remaining 12 weeks in both groups, with 120s of active recovery (slow rhythmic swinging of the extremities without the use of elastic bands) between sets and 90s of rest between exercises. The speed of execution of the exercises was controlled using a metronome marking the cadence (2s of concentric contraction and 2s of eccentric contraction). The training session will consist in a general warm-up, 6 resistance exercises, including 2 upper limb exercises (elbow curl and chest press), 2 lower limb exercises (lunge and standing hip abduction), and 2 exercises combining both upper and lower limbs at the same time (squat plus upright rowing and squat plus shoulder press) and finally the cooldown routine. Primarily multijoint exercises were chosen to emphasize both major and minor muscle groups.

The H-SPEED group will perform the same routine than the TRADICIONAL group (the same general warm-up, the same 6 resistance exercises and the same cooldown routine) with the difference that this group will perform the concentric phase of each repetition in the resistance exercises ''as fast as possible'', will pause for 1 second, and will perform the eccentric phase in 2-3 seconds (the speed of execution of the exercises was controlled using a metronome). This group will perform 12 submaximal repetitions with very low perceived exertion (3 of 10) and ''rapid´´ in the qualitative perceived exertion scale for power training, equivalent to 40-50% 1RM (low-intensity). The number of sets per exercise progressed from 3 in the first 8 weeks to 4 in the remaining 12 weeks, with 90s of active recovery between sets (slow rhythmic swinging of the extremities without the use of elastic bands) and 60s of rest between exercises.

The MULTICOMPONENT group sessions will include a resistance training component, but will combine it with additional exercise regimens including balance, aerobic, flexibility and coordination. Participants will perform, in this order, balance exercises followed by resistance/coordination, aerobic/coordination and flexibility exercises in each session. The balance training will consist in static, dynamic and proactive balance exercises. In the resistance training block, the participants will perform 15 submaximal repetitions with a perceived exertion level on the OMNI-RES Scale 6-7 (somewhat hard) in the first 8 weeks and 8-9 (hard) in the remaining 12 weeks. Participants will perform 2 resistance exercises (squat plus upright rowing and lunge) at traditional slow-speed (2s of concentric contraction and 2s of eccentric contraction). The number of sets per exercise will progress from 3 in the first 8 weeks to 4 in the remaining 12 weeks, with 90s of active recovery between sets and 60s of rest between exercises. Given the demonstrated importance of reproducing the different challenges encountered in daily life, will be proposed in the aerobic part of the session exercises that will require moving through space using walking progressively at faster speeds to light skipping, jogging, or with longer steps, and while adding the use of the arms. The heart rate will be monitored by the polar team system, which allows monitoring the heart rate of different people at the same time. The intensity of this part will progress from 65 to 85% of the maximum heart rate over the training weeks. The flexibility block will consist in static stretching exercises of upper and lower limbs. Finally, the coordination exercises will be performed in the rests periods of resistance and aerobic blocks, and will consist of psychomotor (reaction time) exercises, dance movements and obstacle exercises. Specific cognitive challenges were integrated also into this block (coordination) to engage executive function, and to specifically stimulate the inhibition of habitual responses and cognitive flexibility. For instance, participants will have to perform task sequences while reversing or ''scattering'' a learned order, or to learn different stimulus-response associations and then switch between them according to external cues. The difficulty of balance and coordination exercises will increase progressively to generate adaptations.

The subjects will perform four sessions of pre-intervention familiarization to (a) select the color, grip width, and number of bands; (b) adapt the rate of perceived exertion; and (c) learn the correct technique for the exercises. The loads will be adjusted every week to maintain the appropriate training intensities by adapting the color and number of elastic bands along with the grip width. Training attendance will be recorded at every session. All the training sessions will be performed in two Municipal Activity Centers for Older People located in Valencia (Campanar and Nou Benicalap centers), under the supervision of a qualified and experienced sports scientist and physiotherapists to ensure safety and compliance.

All the supervised programs will include 2 weekly sessions will perform on nonconsecutive days (separated by 48-72 hr) for 20 weeks. Each session will be performed in groups, and each participant always will perform the exercises in the same order, alternating between the upper and lower limbs. Elastic bands (TheraBand®, Akron, OH, USA) and chairs will be used as the equipment.

Inclusion Criteria:

• Age>60 years.
• Physically independent (able to walk 100 meters without a walking aid and climb 10 steps without rest).
• Medical certificate of suitability or fitness to practice resistance training activities.
• No plans to leave the area during the intervention.
• Cognitive ability to understand, follow the instructions and sign the informed consent form.
• Free of any antioxidant supplements for at least 6 weeks before the start of this study.
• Willingness to be randomized to either intervention group and to follow the study protocol.

Exclusion Criteria:

• Presence of cardiovascular, musculoskeletal, renal, liver or neuromuscular disorders that would prevent the participant from performing the exercises.
• Body weight changes >10% in the previous year.
• Intake of prescription medications that were expected to alter the results of the study (ergogenic, dietary aids, estrogen, steroid hormones, calcitonin, or corticosteroids).
• A history of malignant neoplasms.
• Engagement in regular strength training (more than once a week) during the previous 6 months.
• Individuals participating in another research project (within the last 6 months) involving dietary, exercise and/or pharmaceutical intervention
• Mini Mental State Examination lower than 24/30
• Severe visual or hearing impairment

For masking the participants, the investigators will not inform participants of what group they will be in. For outcome assessor, data collectors and data analysts independent people will be use, and if this is not possible, a random code will be created for each participant so that it is not possible to identify which group belongs to.