Luke Peddie’s MSc Thesis Defence

Title: Acute effects of outdoor versus indoor exercise: a systematic review and meta-analysis

Thesis Supervisor: Dr. Eli Puterman
Committee Members: Dr. Michael Koehle, Dr. Guy Faulkner
Chair: Dr. Mark Beauchamp

Abstract: Physical activity and exposure to nature have each been recognized for their positive effects on health and wellbeing. When taken in tandem, outdoor exercise is proposed to have additive benefits compared to exercising indoors or being inactive outdoors. Previous reviews of green exercise have reported inconclusive findings due to a paucity of high-quality evidence. The present review sought to summarize the body of literature that compares physiological and perceptual differences of a single bout of exercise in outdoor spaces versus indoor spaces.

Following the PRISMA reporting guidelines for systematic reviews, a search was conducted in nine databases for any articles published before November 2019. When studies and outcomes were methodologically uniform, quantitative analyses was completed. Vote counting and harvest plots were used to synthesize the remaining outcomes. Quality of articles was assessed using the Cochrane Risk of Bias Assessment Tool.

The findings of 24 articles (Total N = 757) were examined. Summarized outcomes include objective exercise intensity, perceived exertion, performance, neuroendocrine responses, cardiovascular responses, thermoregulation, enjoyment, intention for future exercise and perceptions of the environment. Meta-analysis was conducted for measures of mean heart rate, perceived exertion, mean speed, time to completion, enjoyment, and future intention for exercise. Significant effects of the environment were detected for meta-analyses of perceived exertion (g = -0.84, 95% CI = [-1.60, -0.09], p = 0.03) and enjoyment (g = 1.24, 95% CI = [0.59, 1.89], p < 0.001). Methodological diversity made it impossible to statistically summarize the remaining outcomes, results split between no effect and statistically significant changes, resulting in inconclusive findings. The majority of included studies (54%) were assessed to have a high risk of bias and all other studies (46%) were assessed to have some concerns of risk of bias.

Although no additive physiological benefits were identified by the present review as result of exercising outdoors, exercise still presents well-documented potential for improved health. When performed at an equivalent objective intensity, outdoor exercise appears to be easier and more enjoyable than indoor exercise. Outdoor exercise may be more likely to be repeated and more sustainable, allowing physiological benefits to accrue over repeated bouts.