Frailty is a highly prevalent condition, reaching approximately 7% to 30% of older adults aged from 65 up to 80 years [2]. Although exercises seemed to be beneficial for the frail elders, there is still insufficient evidence to indicate the appropriate modality, frequency and intensity of physical exercises that were able to improve physical functioning in this population [9]. The virtual reality (VR) using interactive games (exergames) have generated broad scientific and clinical interest in recent years[10]. Studies indicate that older adults can benefit from training with exergames in improving mobility [12, 13], lower limb strength [14], cognition, particularly executive function [13], body balance [10, 15-18], reaction time [12] and may contribute indirectly to prevent falls [10, 19, 20]. But, there is still insufficient evidence to suggest that the use of exergames are superior even to other types of intervention [21-23] or in combination with conventional physiotherapy [24] The purpose of this study is to investigate the effectiveness of adding exercises using interactive videogames (exergames) in improving physical functioning on frail and pre frail older people when compared to conventional physiotherapy. A parallel randomized clinical with a 6 month follow-up period will be conducted with 82 frail community dwelling older adults. Participants randomized to the Experimental Group will be submitted to 30 minutes of conventional physiotherapy and 20 minutes of therapy using interactive games Xbox 360 Video Game and Entertainment Microsoft System with Kinect sensor.

The Control Group will receive 50 minutes of conventional physiotherapy. Both groups will receive 50 minutes of intervention twice a week for 12 weeks. Primary outcomes will be assessed by the Short Physical Performance Battery, the Usual walking speed test and Four Step Square Test in the baseline, 3 and 6 months after that.

Frailty is considered a biological geriatric syndrome, characterized by a decreased resistance to stresses and functional reserve due to the cumulative decline in multiple physiological systems, with consequent increased state of vulnerability [2]. Negative health related outcomes, such as disability, recurrent hospitalization, institutionalization, falls and mortality [2-4] are associated with frailty, considered an emerging public health problem [2, 5]. Physical exercise has been recommended as an intervention strategy for the prevention and rehabilitation of the mobility-related outcome in the frail elderly whit positive impact on functional capacity and performance [8].

A functional downward spiral characterized by an impairment of several functional domains, such as strength, muscular endurance and motor-cognitive processes, ultimately leading to restricted mobility and decreased physical activity level is commonly observed in frail older people. Interventions that promote the integration of multisensory, cognitive and motor skills can be able to motivate the older people to remain more active for longer periods, despite their limitations. Exergames involve tasks in virtual environments that combine physical and cognitive demands in an attractive and challenging way. The player is encouraged to achieve goals and overcome limits during the game, providing immediate feedback in relation to their performance. The game experience can create a greater sense of self-efficacy and generate a more positive perception of personal skills, modulated by a positive environment reinforcement, consequently increasing motivation and engagement. This combination of greater sense of self-efficacy and greater motivation could provide a positive and necessary influence for most older people to overcome their limitations and create new lifestyle habits [25], decreasing disability. This study sought to investigate the effectiveness of adding exercises using interactive videogames (exergames) in improving physical functioning on frail and pre frail older people when compared to conventional physiotherapy.

Inclusion Criteria:

Community dwelling older adults without severe cognitive impairment (defined as a Mini Mental State Examination (MMSE) score adjusted according to the educational level with reference cutoff scores of: 13 points for those who are illiterate, ; 18 points for those with elementary and middle levels, and 26 points for those who have a high level 26), without any physiotherapy intervention for at least three months and classified as frail or pre-frail, according to the phenotype of frailty using Fried et al. criteria:

1. Unintentional weight loss of ≥ 5% or ≥ 4.5kg body weight in the previous year.
2. Exhaustion assessed by self-reported fatigue, indicated by two questions of the Center for Epidemiological Studies - Depression: (a) I felt that everything I did was an effort; (b) I could not get going. . Subjects answering "2" or "3" to either of these questions are categorized as frail by the exhaustion criterion.
3. Decreased grip strength (kg/force) in the dominant hand adjusted according to sex and body mass index (BMI). The cutoff for grip strength (Kg) criterion for men 2will be: BMI ≤ 24 grip strength ≤ 29; BMI 24,1 - 28 grip strength ≤ 30; BMI > 28 grip strength ≤ 32. The cutoff for grip strength (Kg) criterion for women will be 2: BMI ≤ 23 - grip strength ≤ 17; BMI 23,1 - 26 grip strength ≤ 17,3; BMI 26,1 - 29 grip strength ≤ 18; BMI > 29 grip strength ≤ 21.
4. Low level of physical activity. Participants will meet the criterion for physical inactivity if, in the last two weeks they did not perform a planned physical activity at least twice a week lasting more than 30 minutes or, if they did not perform planned or unplanned walks lasting for more than 15 minutes at least twice a week or, if they had performed any moderate or vigorous housework activity (> 2,5 METS) such as: wash or mop the floor, vacuuming, washing windows or wash the car frequently at least 1x a week for 30 minutes.
5. Slow walking speed. The time to walk a 4.6 meters path, with two meters for acceleration and two for deceleration, will be measured The velocity for each participant will be recorded. Those with a gait speed equal or less than 0.8 m/s will be considered frail.

Exclusion Criteria:

Severe visual impairment that prevents interaction with video games, if they had a localized loss of muscle strength and/or changes in postural tone that impede the execution of safe displacement movements in the standing position, without the aid of another person and, if they present chronic or acute diseases that contra-indicate therapeutic exercises.