The influence of anthropometric variables, body composition, propulsive force and maturation on 50m freestyle swimming performance in junior swimmers: An allometric approach.

The purpose of the current article was to use allometric models to identify the best body size descriptors and other anthropometric variables, body composition, and offset maturity that might be associated with the youngsters' 50m personal-best (PB) swim speeds (m·s-1). Eighty-five competitive swimmers (male, n=50; 13.5±1.8 y; female, n=35; 12.6±1.8 y) participated in this study. Height, body mass, sitting height, arm span, skinfolds, arm muscle area (AMA), and maturity offset were assessed. Swimming performance was taken as the PB time recorded in competition, and the propulsive force of their arm (PFA) was assessed by the tied swimming test. The multiplicative allometric model relating 50m PB swim speeds (m·s-1) to all the predictor variables found percentage body fat as a negative [(BF%) ß= -.121±.036; P=0.001], and PFA (PFA ß=.108±.033; P=0.001) and the girl's arm span (ß=.850±.301; P=0.006), all log-transformed, as positive significant predictors of log-transformed swim speed. The adjusted coefficient of determination, Radj2 was 54.8% with the log-transformed error ratio being 0.094 or 9.8%, having taken antilogs. The study revealed, using an allometric approach, that body fatness and PFA were significant contributors to 50m freestyle swim performance in young swimmers.

Are there gross motor coordination spurts during mid-childhood?

OBJECTIVES: The aims of this study were (1) to identify the timing of the mid-growth spurt (MGS) in stature in children and (2) to identify gross motor coordination (GMC) spurts when aligned by the age of attainment of the MGS (aMGS). METHODS: Stature, weight, and GMC were measured in 245 Portuguese children followed annually from 6 to 10 years. GMC was assessed and to estimate children's MGS in stature as well as GMC spurts in each of the four tests aligned by aMGS, we used a nonsmoothed polynomial methodology. RESULTS: In boys, the aMGS was attained at 7.8 years, whereas in girls it was 8.0 years. In boys, the peak MGS was 6.2 cm∙yr-1 and in girls it was 6.4 cm∙yr-1 . In boys, the peak for walking backwards (WB) occurred 18 months before aMGS (14.9-points∙yr-1 ), jumping sideways (JS) was 12 months after aMGS (13.5-points∙yr-1 ), hopping on one leg (HO) was 18 months before aMGS (11.7-points∙yr-1 ), and shifting platform (SP) was 12 months before aMGS (6.8-points∙yr-1 ). In girls, WB spurts occurred 12 months after aMGS (13.3-points∙yr-1 ), JS was 12 months before aMGS (10.5-points∙yr-1 ), HO was coincident with aMGS (10.4-points∙yr-1 ), and SP was 18 as well as 12 months before aMGS (7.2-points∙yr-1 ). No differences were observed in the mean peak spurts between sexes in the GMC tests. CONCLUSIONS: Boys and girls reached their MGS in stature at about the same chronological age. Spurts in GMC did not express themselves in the same biological timing relative to aMGS in stature, and there are sex differences.