Healthy Lifestyle Program to Improve physical literacy and Physical Fitness of Junior High School Students: A Quasi-Experimental Approach

Objectives. This quasi-experimental study aimed to evaluate the effectiveness of the Healthy Lifestyle Program (HLP), integrated into regular physical education classes, in enhancing physical literacy and physical fitness among junior high school students aged 13–14, while addressing sedentary behaviors associated with high screen time and limited outdoor play. Materials and Methods. Seventy-two eligible students (mean age = 13.6 ± 0.4 years; 19 males and 17 females per group) were allocated to an experimental group (EXP; n = 36) or a control group (CON; n = 36) using a non-random assignment based on intact classes, consistent with a quasi-experimental design. The EXP group participated in the HLP, which consisted of weekly 80-minute sessions incorporating warm-up activities, motor skill activation, fitness circuits, small-sided games, classroom active breaks, and home-based physical activity assignments at a target intensity of Borg RPE 12–14, complemented by weekly healthy lifestyle education. The CON group followed the standard physical education curriculum. Physical literacy was assessed using the Indonesian-adapted Adolescent Physical Literacy Questionnaire (APLQ; Cronbach’s α = 0.951), and physical fitness was measured using the Indonesian Physical Fitness Test (TKJI; validity = 0.720; reliability = 0.920). Inter-rater reliability was high (APLQ ICC = 0.82; TKJI ICC = 0.88). Program content validity was confirmed using Aiken’s V (0.94). Data were analyzed using descriptive statistics, Shapiro–Wilk tests for normality, Levene’s tests for homogeneity, and MANOVA with partial η² effect sizes. Results. Baseline scores were comparable between groups. The EXP group demonstrated substantial improvements in physical literacy (gain = 24.75 ± 14.52) and physical fitness (gain = 6.94 ± 2.51), whereas the CON group showed minimal change (physical literacy gain = −0.44 ± 2.18; physical fitness gain = 0.08 ± 0.60). MANOVA revealed a significant multivariate effect (Wilks’ Λ = 0.180, p < 0.001), with large effect sizes for both physical literacy (η² = 0.602) and physical fitness (η² = 0.785). All statistical assumptions were met. Conclusions. The Healthy Lifestyle Program significantly improved physical literacy and physical fitness among early adolescents. These findings support the integration of educationally grounded, multicomponent lifestyle programs into school curricula, such as Kurikulum Merdeka, to address sedentariness using accessible and contextually appropriate resources. Future research should examine longer intervention durations and more diverse socioeconomic contexts.