Effect Of Different Types Of Upper Body Strength Training Within Gym Class On The Distal Radius BMD Of Junior Middle School Students

In recent years, research on the effect of strength training on children and adolescents’ skeleton has received world-wide attention. Compared with the relative mature theory research, the relevant experiment research has been in the stage of exploration, especially in the correlations between the type, intensity and duration of strength training and bone mineral density (hereinafter referred to as BMD).This thesis adopts the methods including literature data, questionnaire survey, measurement, experiment and mathematical statistics. By conducting a 17-week experiment among the 97 junior one students in the three classes in Minhang Third Middle School, it explores the difference of effect of various types of upper limb strength training on the BMD of distal radius (hereinafter referred to as DR). Based on the variables of genders, BMI leves, grip strength levels and bone mass, this thesis explores their correlations, aiming to find a solution to optimize the access of bone mass, reduce the incidence of fracture in children and adolescents and conduct the strength training in PE class for reference.Results:(1) After the 4 times* 17 weeks’ moderate intensity strength training, compared with the students in control group, there is a remarkable growth in the BMD of DR among the students of the static training group and dynamic training group, which is a significant difference (P=0.000<0.01).(2) After the 4 times* 17 weeks’ moderate intensity strength training, there is a larger increment in the BMD of DR in male students than female students in the static strength training group, which is a significant difference (P=0.012<0.05). While there is no significant difference between the dynamic strength training group and the control group (P> 0.05).(3) After the 4 times* 17 weeks’moderate intensity strength training, there is a remarkable growth (P< 0.05) in the BMD of DR in the normal-weight students and the underweight students in the static strength training group as well as the dynamic strength training group. But there is no significant difference between the above two groups (P>0.05). In contrast, there is no significant growth in the BMD of DR in the overweight students in the above two groups (P>0.05).(4) After the 4 times* 17 weeks’moderate intensity strength training, there is a remarkable growth (P=0.000<0.01) in the BMD of DR in the students with moderate grip strength in the static strength training group as well as the dynamic strength training group. There is also an obvious growth (P=0.005<0.01) in the BMD of DR in the students below moderate grip strength level in both groups. But there is no significant growth (P>0.05) in BMD of DR in the students above the moderate grip strength level in both groups.(5) After the 4 times* 17 weeks’moderate intensity strength training, there is an obvious growth (P<0.05) in the BMD of DR in the students with normal bone mass level in the static strength training group as well as the dynamic strength training group. While for those students with an initial low bone mass level, there is a significant growth (P<0.01) in the BMD of DR in both groups, but there is no obvious difference between the above two groups (P>0.05).Conclusions:(1) Both the dynamic strength training and the static strength training are effective in contributing to the growth of the BMD of DR among junior one students. And the results further prove that the actions through muscles pulling on bones may result in the change of BMD.(2) For the female junior one students, the dynamic upper limb strength training is more effective than the static upper limb strength training in the BMD of DR. While for the female students, there is no significant difference.(3) For normal-weight or underweight junior students, both the static upper limb strength training and the dynamic upper limb strength training are effective in the growth of the BMD of DR, but there is no significant difference in the two types of training. While there is no obvious effect on the growth of the BMD of DR for the overweight students.(4) For the junior one students with moderate grip strength level, both the static upper limb strength training and the dynamic upper limb strength training are effective in the growth of the BMD of DR. But for the students below the moderate grip strength level, only the dynamic strength training is effective in the growth of the BMD of DR. Meanwhile, for the students above the moderate grip strength level, there is no significant change in their BMD of DR.(5) Compared with junior one students with initial normal bone mass, the static upper limb strength training and the dynamic upper limb strength training have a more significant effect on the students below the normal bone mass level.