Effects of Bioelectrical Impedance-Derived Fat and Lean Mass on Fitness Levels in 8- to 13-Year-Old Children

Childhood obesity prevalence is continuing to rise in developed countries, including New Zealand. The effect of increased adiposity on children’s fitness is relatively unresearched, particularly when using methods other than BMI or skinfold thickness to estimate body fatness. The purpose of the study was to examine the association between fitness and bioelectrical impedance-derived body composition in children. Participants (n = 54) performed a treadmill run to exhaustion, a countermovement vertical jump, and 10m sprint test within 2 weeks of each other. Lean and fat mass were estimated via bioelectrical impedance (MF-BIA2; InBody 230, Biospace, Seoul, Korea). Pearson correlations showed that in females, higher fat mass percentage was associated with lower countermovement jump (r = -0.57), longer 10m sprint time (0.51) and a lower VO2peak performance (-0.48). In boys, higher fat mass percentage was associated with lower VO2peak (-0.36). In both boys and girls lean mass percentage was highly correlated with improved performance in all fitness tests (r = 0.40-0.70). We conclude that lean mass in all cases has a beneficial effect on performance, whereas fat mass tends to be detrimental to girls performance and is likely to be detrimental (VO2peak) or possibly beneficial (countermovement jump) in boys physical performance.