Normative data for tests of neuromuscular performance and DXA-derived lean body mass and fat mass in pre-pubertal children

Aim: To present gender-specific normative data on estimates of neuromuscular performance, such as muscle strength, vertical jump and standing unilateral balance, in pre-pubertal children. Methods: Lean body mass (kg) and fat mass (%) were estimated by dual-energy X-ray absorptiometry in 246 boys and 190 girls aged 6-12 years in Tanner stages 1 and 2. Isokinetic concentric peak torque at 60 and 180 degrees/sec of the right knee extensors, and flexors were evaluated by a computerized dynamometer. Vertical jump height (VJH) was evaluated with an electronic mat and postural control with a one-leg stand test and a blindfolded one-leg stand test. Results: Anthropometry, muscle strength and VJH in both genders showed improved performance with advancing ages (all p < 0.01 for trend) but there were no constant gender differences across the age groups (all ns.). In boys and girls, the ratio muscle strength/muscle mass showed significantly higher ratios with higher ages (both p < 0.01, respectively), but with no constant gender discrepancy. The postural control tests also showed significantly better performance with higher ages in both boys and girls (both p < 0.01). Conclusion: This report, which provides normative gender-specific data on muscle strength, muscle and fat mass and VJH, shows that in Swedish children aged 6-12 years, there seems to be a linear increase with age and no structural gender differences.