[Association between early menarche and physical fitness among adolescent girls in China].
OBJECTIVE
To explore the association between early menarche and physical fitness among adolescent girls in China.


METHODS
Research material was selected from the data of "2010 National Physical Fitness and Health Survey". Probability unit regression method was used to calculate the age of 10th percentile at menarche and menarche age before the 10th percentile was defined as early menarche(9.0-11.6 years old). A total of 1072 girls with early menarche were selected. Each girl with early menarche was matched with one girl from the same urban or rural locations who hadn't achieved menarche with the age difference less than 0.1 years. A total of 1072 girls without menarche were selected. Indicators of physical fitness included 50 m running, standing broad jump, 50 m×8 shuttle running and sit-ups. Differences of physical fitness between early menarche and without menarche were analyzed using t test stratified by age and urban/rural area. The multilevel models of single dependent variable and multiple dependent variables were used to analyze association between early menarche and physical fitness.


RESULTS
A total of 2144 students were put in this research. Among girls (11.0-11.6 years old) in urban areas, 50 m running, standing broad jump and sit-ups was (9.78 ± 0.85) s, (153.81 ± 18.59) cm, and 27.79 ± 10.25, respectively for those with early menarche, while in girls without menarche was (10.01 ± 0.90) s, (149.71 ± 18.72) cm and 26.28 ± 10.11, respectively. There were significant differences between two groups on all above variables (t values were 4.02, 3.43 and 2.31, respectively with all P values <0.01). Among girls in rural, 50 m×8 shuttle-running and sit-ups was (125.22 ± 15.57) s and 24.96 ± 8.97 for those with early menarche, while it was (120.92 ± 13.06) s and 22.96 ± 9.83 for those without menarche. There were significant differences between two groups on both variables(t values were 3.89 and 2.77 with both P values < 0.01). In addition, 50 m×8 shuttle-running in girls (10.0-10.9 years old) with early menarche was (128.52 ± 15.74) s and it was (123.89 ± 13.50) s in girls without menarche. The difference was significant (t = 2.14, P < 0.05). The multilevel analysis showed that 50 m running, standing broad jump and sit-ups in girls with early menarche was 0.12 s, 3.14 cm and 1.11 higher than girls without menarche (Waldχ(2) values were 4.00, 6.22 and 4.07, respectively with all P values < 0.05). But 50 m×8 shuttle-running in girls with early menarche was 1.95 s less than girls without menarche (Waldχ(2) = 3.96, P < 0.05).


CONCLUSIONS
Early menarche may be associated with higher speed fitness, leg power and muscle power and lower physical stamina.
School of Public Health & Institute of Child and Adolescent Health, Peking University, Beijing 100191, China.
Lian-guo
LG
Fu
Yi-de
YD
Yang
Jun
J
Ma
Hai-jun
HJ
Wang
Yi
Y
Song
Pei-jin
PJ
Hu
Xiao-hui
XH
Li
Li-jing
LJ
Wu
Xiang-rui
XR
Meng
D002648:Child; D002681:China; D005260:Female; D006801:Humans; D008572:Menarche / Q000502:physiology*; D015233:Models, Statistical; D010809:Physical Fitness / Q000502:physiology*; D012424:Rural Population; D013334:Students; D014505:Urban Population