Differences in muscle power and aerobic endurance in pre- and post-menarche girls during mid-adolescence: A two-year follow-up study

Abstract

Problem Statement: Research indicates that early- and late-maturing girls’ physical fitness skills are influenced differently by anthropometric changes, initially favouringearly maturing girls. Purpose: The aim of the study, therefore, is to investigate differences in pre- and post-menarche girls’ physical fitness capabilities. Approach:: Over three school years, fifty-eight (N=58) girls with a mean age of 13.51±3.51, were divided at baseline into a pre- (n=13) and post-menarche group (n=45) for comparison of muscular power and aerobic endurance. Measurements were taken annually (2010-2012) providing data over three time points. The Australian Sports Commission (1996) protocol was used. Basic statistics, a Spearman correlation analysis, and a repeatedmeasures ANOVA, adjusted for with a Bonferroni post hoc correction were applied. Results: Developmental differences between the pre- and post-menarche groups were relatively small and insignificant. Early menarche status was to the advantage of power while reaching menarche later positively affected aerobic endurance at younger ages. Changes in these abilities over the follow-up period were different in the groups and levelled out most differences during final measurements. Conclusion: Timing of menarche contributed to differences in muscle power and aerobic endurance of girls, particularly during mid-adolescence, although only on a practical level. The period at and immediately after reaching menarche is characterized by instability, with changes in power and endurance that are associated with menarche status. Influences of somatic and biological growth in same-aged girls of the same age and the influence thereof on power and endurance will only be levelled out 1-2 years after reaching menarche.