The relationship between lower limb alignment and physical fitness in children aged 10-12: A sex-specific analysis using the ALPHA-fitness test battery.

BACKGROUND

Physical fitness predicts health outcomes during childhood and later life. While the influence of obesity on physical fitness is well established, the impact of lower limb alignment (such as knee alignment, foot posture, and plantar footprint) on physical fitness has been less explored.

OBJECTIVE

To evaluate the relationship between lower limb alignment, body mass index (BMI), and physical fitness in children aged 10-12 with a sex-specific analysis.

METHODS

Fifty-nine children (33 girls, 26 boys) participated in this cross-sectional study. Knee alignment (genu valgum, normal), foot posture (using FPI-6), and plantar footprint (classified by the Hernández-Corvo method) were measured. BMI was calculated to classify children into underweight, normal weight, overweight, and obese. Physical fitness was assessed using the ALPHA-Fitness Test Battery, measuring cardiorespiratory fitness, muscular strength, and speed/agility. Multiple linear regression models were developed to analyse the associations between variables.

RESULTS

Sex and BMI were significant predictors of muscular and cardiorespiratory fitness, with boys presenting better muscular and cardiorespiratory fitness. Larger BMI was associated with poorer muscular fitness (p = 0.003). Knee alignment in the frontal plane was not a predictive factor in physical fitness. Pronated foot was a weak predictor of lesser muscular fitness (p = 0.041). Plantar footprint did not significantly predict physical fitness.

CONCLUSIONS

Sex and BMI were the main determinants of physical fitness. Despite some musculoskeletal factors having some influence, their relationship with physical fitness is not as direct as sex and BMI. Clinical practice should prioritise weight control in the interventions for physical fitness in children, considering sex differences.