The World Health Organization recommends for older adults the same amount of aerobic physical activity as for adults aged 18–64 years, i.e. at least 150 min weekly (about 30 min 5 days a week) of moderate-intensity physical activity. WHO also recommends to perform physical activity to enhance balance and prevent falls on 3 or more days per week, and muscle-strengthening activities involving major muscle groups on 2 or more days a week (http://www.who.int/dietphysicalactivity/pa/en/index.html).
It is known that older people are less keen than younger adults to attend gyms regularly, both because of different aptitudes and because of economic reasons.
We conducted the PoliFIT study to test the efficacy of an Adapted Physical Activity (APA) group-based 4-month programme on the physical performance of a group of 70 years old or older community dwelling adults living in Milan. The study was based on a methodological sound design (i.e. a randomized trial with a waiting list control) that also allowed every participant to attend the programme. The study has been run in collaboration with A.N.T.E.A.S. (Associazione Nazionale Terza Età Attiva per la Solidarietà), an association of older volunteers, and was endorsed by the Municipality of the city of Milan.
The Adapted Physical Activity is defined as an activity relates to movement, physical activity and sport in which emphasis is given to the interests and abilities of individuals characterized by disadvantaged physical condition, such as the disabled, sick or elderly people [International Federation of Adapted Physical Activity (IFAPA) - 9° International Symposium – Berlin, 1989]. It is based upon an attitude of acceptance of individual differences, it advocates access to active lifestyles and sport, and promotes innovation and cooperative service delivery programs and empowerment systems.
Our APA programme consisted in aerobic, strength, balance, coordination and flexibility exercises. It was delivered to groups of 10 people as weekly sessions of 45 minutes. The intervention finished in July 2016. The second cycle of activity offered to the control group has just finished. 
The attendance has been always very high. People enjoyed being there together.
We are now analysing the results of the PoliFIT study, and planning to conduct a follow-on study (the PoliFIT-INFOcus study) testing the effect of different strategies to promote aerobic physical activity based on walking and exercises for balance,  lexibility and strength training, which the older adult can safely perform at home. This follow-on study has been designed to test the FOCUS guidelines on interventions to prevent or treat frailty in older ages when implemented in practice.