[Evaluation of isometric force in lower limbs and body composition in preterm infants]

Introduction: Strength is a physical quality with a clear influence on quality of life. It is determined by the structure of the musculoskeletal system, and depends on the muscular structure. It has been described that prematurity conditions both qualities. The aims of this study are to determine whether prematurity is associated with strength or body composition and evaluate the relationship between prematurity, strength and muscle mass.

Material and methods: Case-control study. Participants were premature 7-to-11 year-old children and full-term birth controls. Strength was measured by a strength gauge and body composition from DEXA (duel-energy X-ray absorptiometry) scans. A total of 89 subjects were included and divided into three groups: 30 prematures with birth-weight ≤ 1500g, 29 prematures with birth-weight 1500-2000g, and 30 controls.

Results: Weight and BMI z-score was lower in the premature group. No differences were found in muscular mass or strength between groups. A ratio was established between strength and weight or muscular mass. It was observed that it was possible for them to move four times their weight, without finding any differences between groups or a relationship with birth-weight.

Conclusions: Between 7 and 11 years of age, children who were premature have lower weight and BMI than the rest of the children. However, there were no differences in body composition or strength between preterm children and controls.