Physical activity is effective in preventing and treating many of these age-related diseases. However, two thirds of Dutch older adults do not reach the recommended level of physical activity.... Show morePhysical activity is effective in preventing and treating many of these age-related diseases. However, two thirds of Dutch older adults do not reach the recommended level of physical activity. Current efforts to increase physical activity with professional led physical activity interventions are effective during the intervention period, but do not manage to have a sustainable effect. In this thesis we studied the possibility of peer coaching to sustainably increase physical activity in older adults. We do this by studying the effectiveness, implementation and organization of peer coach physical activity intervention. The conclusion of this thesis is that older adults can effectively and sustainably increase physical activity of older adults through peer coach physical activity interventions. After a small investment for implementation, a sustainable self-organising exercise intervention can be created which exist for years. The reach of the groups can be increased through an exercise referral scheme in primary care, but the effectivity needs to be improved through research. Nationwide implementation of exercise groups for older adults is possible, but it requires effort from a large (governmental) party. Show less