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Both physical activity (PA) and nature exposure are associated with several youth health benefits. However, the health outcomes when being physically active in nature, called Green Exercise (GE), are less clear. Thus, the purpose of this systematic review was to provide an overview of the psychosocial and physiological outcomes of GE in children and adolescents and to outline future GE research directions. The PRISMA statement guided the review. Web of Science, PubMed, ERIC, and APA PsychNET were systematically searched in February 2019, including studies between 2000 and 2019. Fourteen of 1175 identified publications were included, which reported 15 different psychosocial and six different physiological outcomes, with some studies reporting more than one outcome. For 16 outcomes, studies reported either similar or no effects for both GE and comparison groups. For six outcomes, studies reported stronger effects for GE, for three outcomes, studies reported stronger effects in the comparison group. Evidence was rated as weak, using the EPHPP tool. Thus, GE does not have deleterious effects for children and adolescents compared to PA in other settings. GE might be beneficial; however, due to the study’s heterogeneity and quality, it is premature to make definite conclusions. Future research should build the quality of evidence for GE, use more rigorous research designs, and investigate the underlying effects and mechanisms of GE.

Background: Several theories have been established to explain physical activity (PA) participation. However, many of these theories might not be applicable to adolescent PA behavior as they require a high level of cognitive reflection. Weiss suggests a model for youth which is based on the theoretical concept of Harter, focusing on self-esteem within social, emotional, and developmental aspects to explain behavior. The aim of this study was to test the original and a social support focused alternative version of the Weiss-Harter-model, and to cross-validate the findings in two separate studies. Methods: Data from two cross-sectional studies was retrieved and the models tested using structural equation modeling. Participants aged 11-17 years were recruited from a school (Study 1: N = 182) and from the German MoMo study (Study 2: N = 2,274). They filled in questionnaires about perceived competence, social support, self-esteem, PA enjoyment, and minutes of moderate-vigorous PA (MVPA). Results: None of the studies showed a good model fit for the original model [Study 1: CFI = 0.870, RMSEA 0.118 (90% CI 0.081-0.158), χ 2 = 38.7, p < 0.01; Study 2: CFI = 0.871, RMSEA 0.148 (90% CI 0.140-0.155), χ 2 = 1112.6, p < 0.01], explaining only 12% and 17% of MVPA variance, respectively. The alternative model which added the direct paths of social support to MVPA and PA enjoyment had a very good model fit for both Study 1 [CFI = 1.000, RMSEA 0.000 (90% CI 0.000-0.031), χ 2 = 4.8, p > 0.05] and Study 2 [CFI = 0.990, RMSEA 0.043 (90% CI 0.035-0.051), χ 2 = 103.7, p < 0.01]. The addition of these paths led to changes in effect size and directions of other path coefficients, with self-esteem having a small to meaningless impact on MVPA. The revised models accounted for 38% and 42% explained variance in MVPA, respectively. Discussion: The prominent role of self-esteem in the original model could not be confirmed. Instead, the results emphasize the role of social support for PA and PA enjoyment, which is in line with current research. Interventions to increase adolescent PA levels should thus focus more on components of social support instead of selfesteem. Future studies are needed to examine the interplay between social support, PA enjoyment and perceived competence as PA determinants.

Background: University students are prone to sedentary behavior (SB) which is associated with multiple negative health outcomes. Sit-stand desks may allow for a reduction of SB through standing bouts. To promote standing in university students, decisional cues might be a low-cost approach that can easily be implemented. Purpose: To investigate the effects of decisional cues on students' SB, standing, and active behavior. Method: Over 3 weeks, students were observed in a building on a German university campus, which provides sit-stand-desks in study areas, using an adapted version of the SOPLAY protocol. Baseline data was collected in the first week (T1), before posters and table plaques containing decisional cues were set up in the study areas. Effects were measured in the following 2 weeks (T2 and T3). Results: 2,809 (33% female) students were observed. Sitting decreased from 92.9% [SD = 14.9] to 84.5% [SD = 22.1] from T1 to T3 [ F (1, 141) = 15.6; p < 0.01; η 2 = 0.10]. Standing increased from 5.6% [SD = 13.5] to 10.9% [SD = 14.4] [ F (1, 141) = 9.0; p < 0.01; η 2 = 0.06] and being active from 1.5% [SD = 6.9] to 4.5% [SD = 14.8] from T1 to T3 [ F (1, 141) = 4.2; p < 0.05; η 2 = 0.03). Main effect analyses revealed more students standing in the afternoon compared to morning and lunchtime [ F (2, 140) = 3.2; p < 0.05; η 2 = 0.04). Discussion: Decisional cues could decrease students' SB and promote standing or being active as alternatives. Future research should use a more rigorous study design. The content of the decisional cues should be explored more and expanded to other health promotion areas on campus.

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