The academic performance of secondary students can be affected by several factors. The present study aimed to evaluate whether the body mass index, upper-body strength, lower-body strength, and sports engagement can influence academic outcomes. For such purpose, 328 students (47.9% girls, 52.1% boys, age: 14.58 ± 1.52 years) from one high school in Valencia (Spain) answered a self-reported online questionnaire enquiring about their sports engagement after school. Afterward, they underwent anthropometric measurements (height [cm], weight [kg], and body mass index [kg/m2]) and physical tests (handgrip strength [kg], and countermovement jump [cm]). Additionally, we accessed the academic record to calculate the academic outcomes of each participant (average grades and physical education marks). Groups were formed according to body mass index (underweight, normoweight, overweight), strength (weak, normal, strong), and sports engagement (no sport, non-federated sport, and federated sport). We conducted robust one-way analyses of variance with Welch’s correction for each independent variable (i.e., body mass index, upper- and lower-body strength, and sports engagement) to evaluate their influence on academic outcomes. A significant effect of the body mass index on the average grades (F= 7.085, p= .001, ηp2= .038) and physical education marks (F= 8.145, p= .001, ηp2= .046) was encountered, with significantly better results for both the underweight (mean difference [m.d.] 0.80, 95% confidence interval [CI] 0.10 – 1.51, p= .020) and normoweight students (m.d. 0.77, 95%CI 0.25 – 1.29, p= .002) compared to those overweighted. The strength did not show significant effects on the academic outcomes (all p > .373). Finally, sports engagement showed a significant effect on the physical education marks (F= 17.625, p< .001, ηp2= .099) but non-significant effects on the average marks (p = .125, ηp2= .013). In this regard, the students participating in federated sports obtained the best marks compared to those students who do not practice federated sports (all p< .001). With these results in mind, academic institutions may implement academic enhancement programs focused on promoting active lifestyles, weight control, and sports participation to improve academic outcomes of students. Future research should elaborate on the mechanisms that mediate the effects of the independent variables (body mass index and sports engagement) on academic outcomes.

Keywords: Strength, relative strength, body composition, academic performance, adolescents, school.