A Randomized Trial of High Intensity Circuit Training in Nature and Indoors to Compare Exercise Performance, Emotions, Perceived Exertion, and the Variability of Movement and Heart Rate in Recreational Exercisers.

Introduction: Nature environments are "any outdoor spaces that retain noticeable elements of nature, ranging from pristine or seminatural areas to urban green or blue spaces, including green infrastructure". Exercising in nature settings has been shown to improve well-being outcomes such as lower anxiety and greater positive mood, more so than exercising in artificial environments like urban spaces or indoors.

Over the past decades, the well-being benefits of nature-based exercise have been extensively reported in the literature, but exercise and sport performance have not been studied as much, in spite of some studies showing that performance may be better in natural settings than indoor conventional settings (e.g., dancing more vigorously, more power in cycling, ability to run more distance until exhaustion). This raises the question of how nature may impact performance efficacy (the product of performance, i.e., running faster) and efficiency (the psychological and physiological processes that may enhance performance efficacy) in exercise and sport activities, especially since many studies show, for example, that achieving the same goal in nature is less effortful than doing the same activity indoors.

The relationship between the exercise factor and the environment factor for potential health and performance benefits can be seen as sub-additive (less than total independent benefits of both exposures), additive (equal to the sum of the parts), and synergistic (greater than the sum of the parts).

Mechanisms: The mechanism by which physical activity in nature environments induces greater health and may enhance performance is not yet fully understood. Historically, the exercise and sport communities have created "proper" spaces to undertake their physical activities, such as gyms, stadiums, tracks. However, these standardized and artificial spaces are believed to offer limited variability in action. The ecological dynamics perspective views nature settings as a more varied and challenging landscape of affordances (possibilities for action) than that of built environments. Variability in the environment turns into variability in body systems, allowing for degenerate behavior (changing movement structure without compromising functionality). Assuming that the nature environment presents a richer and more variable landscape of affordances to exercisers has given birth to a theory within the ecological dynamics framework, labelled EVA, or the Empowering Variability of Affordances of Nature. To this end, EVA assumes that the uneven surfaces, objects and obstacles of nature settings such as grassland and trees allow for more variable athletic behavior, which has been deemed beneficial for exercise and sport performance. It must not be a coincidence that activities mostly practiced in natural environments such as extreme sports, are notorious for their demand for adaptability and creativity, and for promoting health.

Furthermore, for exercisers, the nature environment is known to elicit dissociative/exteroceptive attentive focus (i.e., focus on the environment), while the built/indoor environment elicits associative attentive focus (i.e., focus on the task itself). An associative cognitive process (focus on the task) is known to cause lower affective responses and greater exertion during exercise, particularly in high intensity physical activities. In short, exercising in nature may improve wellbeing and athletic performance due to inherent variability in action, and by eliciting exteroceptive attentive focus.