**Background:** Athletes’ performance is a dynamic, non-linear, and multidimensional phenotype that results from complex interactions between individual and environmental factors. The ecological systems theory (Bronfenbrenner, 1977) provides a framework for understanding these interactions across hierarchical levels: the micro-level (intrapersonal and training characteristics, coach-athlete dyad, family support), meso-level (sports clubs, federations), and macro-level (culture, economy, demographic indicators). Previous research has shown that population size, Human Development Index (HDI), and political systems can explain up to half of the performance variance between countries. For example, athletes from cities with high HDI were six times more likely to become elite swimmers compared to those from lower HDI cities. In running, the 20 best sprinters worldwide (2006–2016) came from high-HDI countries, while endurance event specialists (10,000 m or above) predominantly came from low/middle-HDI countries, partly reflecting the African phenomenon. Despite growing interest, research on country-level variables and cross-level interactions in running performance remains limited. The InTrack Project was designed to address this gap.
**Methods:** This is a cross-sectional and cross-cultural study. The sample will comprise runners of both sexes from four countries. The expected sample size is at least 80 participants per country (estimated using Gpower 3.1: effect size 0.35; α err prob 0.05; Power 0.95; number of predictors 10). Ethical approval was obtained in Brazil (Federal University of Sergipe, protocol 5.286.914), Kenya (NACOSTI/P/22/18904), and Portugal (CEFADE 12/2022). Eligibility criteria: runners aged ≥18 years, self-classified as a runner, participation in at least one official competition in the last 12 months, and completion of the online questionnaire. Countries are included only after local ethics committee approval. Data collection occurs entirely in a virtual environment. Recruitment is conducted through athletics federations, higher education institutions, social media, personal networks, and sports clubs (2022/2023). After providing informed consent via a web survey, participants complete a 37-item questionnaire (approximately 15 minutes) covering: identification (age, sex); anthropometrics (body height, body mass); sociodemographic profile (country of residence, monthly income, educational level, marital status); training characteristics (volume, duration, frequency/week, sessions/day, practice time, running pace); involvement in official running events; motivation; relationship with coaches; and perception of contextual support (family, friends, coach, training facilities). Mandatory questions include country of residence and running pace (outcome variable). The questionnaire’s psychometric quality will be tested through expert evaluation and a pilot test among Brazilian runners, assessing content, objectivity, clarity, readability, and understanding. Translation and back-translation will be performed for non-Portuguese speakers. Country-level (meso-level) information will be obtained from free-access web pages and documents, including existence of talent development programs, number of high-performance athletes in national/international rankings, number of sports clubs, number of high-performance competitions, and sports investment. Macro-level information includes population size and density, HDI, gross domestic product, per capita income, annual sports investment, number of high-performance athletes internationally, and cultural dimensions (Hofstede’s six dimensions: power distance, individualism, masculinity, uncertainty avoidance, long-term orientation, indulgence). Expected statistical procedures: descriptive statistics (five-number summary, mean/SD, frequencies); multilevel analysis (hierarchical linear models) with intraclass correlation coefficient to quantify variance attributable to country-level grouping; two-level models (level 1: runners; level 2: countries); Latent Class Analysis (LCA) to cluster subgroups based on economic aspects, training characteristics, and environmental perception; Network analysis to examine non-linear interactions and identify hub variables bridging micro and macro levels; and multiple regression models testing additive and multiplicative effects. Confidence intervals will be fixed at 95%. Results will be disseminated via peer-reviewed journals and scientific events, following the Checklist for Reporting Results of Internet E-Surveys (CHERRIES).
**Clinical Implications:** Although this is not a clinical intervention study, the findings are expected to provide scientific support for public policies and sports development programs by identifying environmental characteristics (at micro, meso, and macro levels) that predict runners’ performance within and between countries. Understanding cross-level interactions may help optimize resource allocation, talent identification, and training environment design. The project also aims to fill gaps regarding variables that connect different levels of information, potentially informing strategies to improve both individual and societal outcomes through sport.