Background
The rapid rise in the incidence and the persistent multi-generational occurrence of chronic disease has grave implications for the immediate and long-term health of American Indian and Alaska Native children and the sustainability of our nation’s indigenous people.  Addressing social inequalities contributing to the etiology of multi-generational chronic disease among American Indians and Alaska Natives can occur within this generation’s lifespan.  One potential strategy of a comprehensive public health response may be targeting environmental and policy factors that promote or inhibit exercise, recreational activities, household and occupational activities, and active transportation.  Nevertheless, comparatively fewer studies have examined the associations between chronic diseases and the built environment that are exclusively focused on American Indian and Alaska Native communities; even less direct observational research has focused specifically on the features of the built environment that influence active living.  Far less is known about the role of tribal government in promoting or inhibiting exercise, recreational activities, household and occupational activities, and active transportation through its courses of action, regulatory measures, laws and policies, tribal resolutions, and funding priorities.

Objectives
To advance the state of the science, this review aims to examine the methodology and current evidence on physical activity among American Indian and Alaska Native communities, with particular attention to advancing our understanding of policy, systems and environmental change for promoting active living among these communities.  Taking into account the assets and barriers identified as influential among American Indian and Alaska Native communities, this review also aims to provide guidance on promising strategies and research opportunities to effectively develop, implement, evaluate, sustain and disseminate community changes that promote active living within and across diverse American Indian and Alaska Native communities.

Methods
A systematic review was conducted to identify all peer-reviewed literature addressing physical activity among American Indians and Alaska Natives using three strategies.  First, key words relating to physical activity and American Indian were used to conduct a literature search using PubMed (Medline), Web of Science, and Scopus through May 31, 2014.  In addition, the search engine of Active Living Research, a national program of the Robert Wood Johnson Foundation (http://activelivingresearch.org/) was searched using “Native American”.  The final strategy was searching the United States National Institutes of Health Human Nutrition Research Information Management system database (http://hnrim.nih.gov/) to identify relevant investigators and then conducting a search by their name in PubMed for any missed articles.  The references of each article were reviewed to identify any additional articles. Peer-reviewed studies were considered for review if they included human subjects, were published in English and reported on physical activity among American Indians and Alaska Natives living in the United States.  When possible, the following information was extracted from each study:  year of publication, year of data collection, sample age, sample size used for final analyses, study setting, study design, measures and methods, data sources, psychometric properties, intervening approaches, outcomes, covariates, results, funding, author identified strengths and limitations and author identified lessons learned particular to conducting research or fostering active living among American Indians and Alaska Natives.  One researcher (SF) conducted the search and coded all the articles.  Inter-rater reliability was conducted with high agreement on more than 31 articles categorized as interventions (ER) and 65 of articles categorized as descriptive/associational (RC).

Results
More than 250 articles providing insights on physical activity among American Indians and Alaska Natives have been identified.  Limited work has reported on physical activity patterns across varying life stages and from various geographical settings using objective measures.  More than 90 articles reported descriptive or associational observations providing insights on American Indians or Alaska Natives but a majority of these studies included very small sample sizes.  Few studies focused on measuring physical activity and the built environment associated with active living among American Indian and Alaska Native communities.  Youth interventions were predominantly school-based with one occurring at a childcare center and six having strong child-family-community components.  Few studies reported on community-level strategies to promote physical activity among American Indian and Alaska Native communities, one using a multilevel approach involving school, work site and church.

Conclusions
There is limited and mixed evidence available on physical activity patterns among American Indian and Alaska Native communities.  Family-, school- and community-based approaches have shown promise, as well as integrating cultural and historical connections around healthy living.  Very little research has focused on the role of tribal government actions in fostering community changes that promote active living.

Implications
Tribal leaders have untapped and unexamined potential to accelerate progress in childhood obesity prevention.  More work is needed to understand physical activity and inactivity among American Indian and Alaska Native communities from early infancy into adulthood.  Research is also needed on the role of tribally-led community changes that promote active living.