Social fitness definition and constructs -- Definition -- Constructs -- Measures of social fitness, sources of social fitness, and the link to well-being -- Measures of social fitness -- Social support from family and the link to well-being -- Social support from friends, co-workers, and unit members, and the link to well-being -- Social support from neighborhoods, cyber communities, and imagined communities -- Social networks and well-being -- Negative aspects of social ties -- Summary -- Barriers and bridges to social support -- Intra-individual factors -- Interpersonal factors -- Interventions to promote social fitness -- Efforts related to intra-individual factors and social support -- Efforts related to interpersonal factors and social support -- Efforts related to the influence of social support on well-being -- Conclusion.