Associations of Serum Irisin and Fibroblast Growth Factor-21 Levels With Bone Mineral Characteristics in Eumenorrheic Adolescent Athletes With Different Training Activity Patterns.

PURPOSE: To describe serum irisin and fibroblast growth factor-21 (FGF-21) concentrations in healthy female adolescents with different training activity patterns and their associations with bone mineral properties and metabolic markers. METHODS: A total of 62 adolescent girls aged 14-18 years were recruited: 22 rhythmic gymnasts, 20 swimmers, and 20 untrained controls. Bone mineral characteristics by dual-energy X-ray absorptiometry, daily energy intake by dietary recall, serum irisin, FGF-21, undercarboxylated osteocalcin, and C-terminal telopeptide of type I collagen were measured in all girls. RESULTS: Whole body and lumbar spine areal bone mineral density and lumbar spine bone mineral content were higher in the rhythmic gymnasts group compared with swimmers and untrained controls groups (P < .05). Serum irisin, FGF-21, undercarboxylated osteocalcin, and C-terminal telopeptide of type I collagen levels were not significantly different between the groups. In the rhythmic gymnasts group, serum FGF-21 concentration was positively correlated with lumbar spine areal bone mineral density independently of confounding factors (r = .51; P = .027). CONCLUSIONS: Serum irisin and FGF-21 levels were not different between adolescent eumenorrheic girls with different training activity patterns. FGF-21 was positively associated with lumbar spine areal bone mineral density, which predominantly consists of trabecular bone in adolescent rhythmic gymnasts.

Longitudinal Associations of Body Fatness and Physical Fitness with Cognitive Skills in Preschoolers.

A good cognitive status predicts academic, professional, and health outcomes. However, longitudinal data regarding the associations of body fatness, physical fitness, and cognition are relatively scarce and mixed. The purpose of this longitudinal study was to investigate whether body fatness, cardiorespiratory fitness (CRF), and muscular fitness (MF) in preschool are associated with cognitive skills in the first grade of school. A total of 133 South Estonian children whose age was 6-7 years were recruited from 13 kindergartens and again at 7-8 years after they had entered school. Body fat percentage (BF%), CRF, MF as the mean of z-scores of relative upper-limb strength, standing long jump results, and cognitive skills (verbal, conceptual, and perceptual) were studied. There were no associations between BF% and CRF in preschool with perceptual, conceptual, or verbal skills in school in boys and girls. In boys, a higher MF in preschool was associated with higher verbal skills (ß = 0.293, p = 0.021) in school after adjustment for confounders. Cognitive skills at baseline seemed to be frequently associated with cognitive performance in school. In conclusion, higher MF in preschool was associated with better verbal skills in the first grade of school in boys but not in girls. Body fatness and cardiorespiratory fitness in preschool were not associated with cognitive skills in school.