Correlation between Body Mass Index and Selected Physical Fitness Components among Secondary School Girls in Bangladesh

Abstract

Background: Body mass index (BMI) is a widely used indicator of nutritional status, yet its relationship with health-related physical fitness among secondary school girls in Bangladesh has rarely been examined using a full fitness battery.
Objective: To examine the association between BMI and four components of health-related physical fitness — cardiovascular endurance, muscular strength/endurance, explosive leg strength, and flexibility — among secondary school girls in Bangladesh.
Methods: A descriptive correlational design was used. A total of 140 secondary school girls were selected by purposive sampling. Height and weight were measured to calculate BMI (kg/m²). Fitness was assessed using the Queen's College Step Test, Push-Up Test, Standing Broad Jump Test, and Sit-and-Reach Test. Pearson's product-moment correlation was used; 95% confidence intervals were estimated via the Fisher z-transformation and exact two-tailed p-values were derived from the t-distribution (df = 138).
Results: Mean BMI was 22.54 ± 3.12 kg/m². BMI was significantly and negatively correlated with all four fitness components: cardiovascular endurance (r = −0.48, 95% CI −0.60 to −0.34, p < .001), push-up performance (r = −0.31, 95% CI −0.45 to −0.15, p < .001), standing broad jump (r = −0.42, 95% CI −0.55 to −0.27, p < .001), and, more weakly, flexibility (r = −0.19, 95% CI −0.35 to −0.02, p = .025). By variance explained, BMI accounted for 23.0% of the variance in cardiovascular endurance, 17.6% in standing broad jump, 9.6% in push-up performance, and 3.6% in flexibility.
Conclusion: Higher BMI was associated with lower performance across all four fitness components among secondary school girls, with the strongest associations for cardiovascular endurance and explosive leg strength and a comparatively weak, though statistically significant, association with flexibility. School-based programmes that support healthy BMI through physical activity and balanced nutrition may help protect adolescent fitness, with the largest expected benefit for aerobic capacity and lower-body power.