*2.2. Measurements*

The Chinese Version of the Self-efficacy for Exercise Scale (SEES-C), modified from a previous study [40] by Lee et al. [21], was used to examine the degree of an individual's confidence in exercising regularly. The SEES-C includes nine items rated on an 11-point Likert scale where "0" represents "not confident" and "10" represents "very confident". An example of an item (translated from Chinese) on SEES-C is "How confident are you right now that you could run three times per week for 20 min even if the weather is bothersome to you?". The Cronbach's alpha reliability coefficient of the SEES-C in this study was 0.93, suggesting a high level of internal consistency.

Recreation specialization was measured with nine items modified from previous studies [4,16,41]. It is a measure of a marathoner's level of interest and involvement. The items were modified for this study according to how long-distance running is usually characterized in the Chinese culture. Recreation specialization was measured using three factors: behavior (three items), cognition (two items), and affect (four items). Both the behavioral and cognitive dimensions were rated on a five-point Likert scale ranging from "novice" (score 1) to "expert" (score 5). The affect dimension was rated on a five-point

Likert scale where "1" represents "disagree strongly" and "5" represents "agree strongly". An example of an affect item is "I would rather go running than do other activities". The internal consistency coefficient of recreation specialization dimensions ranged from 0.67 to 0.89. The total scores for recreation specialization were used in mediation analyses.

Flow experience was measured by the Flow Short Scale (FSS) adapted from previous studies [42,43]. FSS includes 10 items for two dimensions, including fluency of performance (six items) and absorption by activity (four items). FSS is translated into Chinese using a forward-backward translation approach. The items are rated on a seven-point Likert scale ranging from "not at all" (score 1) to "very much" (score 7). An example of an item for measuring fluency of performance is "my thoughts/activities run fluidly and smoothly". The Cronbach's alpha values of flow experience dimensions ranged from 0.88 to 0.95. The total scores for flow experience were used in mediation analyses.

The Satisfaction With Life Scale (SWLS), developed by Diener et al. [2], was used to measure people's evaluation of the overall quality of their life. The Chinese version of SWLS has shown good reliability and validity for people of Chinese background [44]. The scale consists of five items rated on a seven-point Likert scale ranging from "disagree strongly" (score 1) to "agree strongly" (score 7). An example of an item is "so far, I have gotten the important things I want in life". The internal consistency coefficient of SWLS was 0.92 in this study.

Based on suggestions included in previous studies [4,45,46], six demographic variables were included in this study as control variables: age, sex, marital status, education, annual income, and membership in a running group.

## *2.3. Data Analysis*

JASP 0.16 [47] was used to analyze all data in this study. The respondent's profile, mean value, and standard deviations were evaluated through descriptive statistics. Internal consistency reliability analysis was used to evaluate the reliability of all constructs in this study. The correlation of all variables was evaluated by a Pearson's correlation coefficient. Furthermore, mediation analyses were used to examine research Hypotheses 1 through 7.
