Dynamic Mechanisms Of Aerobic Exercise And Strength Training On Negative Body Image

Objective:This experiment explored the influence and dynamic mechanisms of8 weeks of physical exercise intervention on negative body image,as well as the moderating effect of exercise type and gender.Methods:First of all,66 inactive college students with negative body image were randomly assigned to the aerobic exercise group and the strength training group by using Body Areas Satisfaction Scale and Physical Activity Rating Scale.Using a univariate longitudinal design,the independent variable was the type of exercise?aerobic exercise vs.strength training?.The dependent variable was negative body image?body satisfaction and social physique anxiety?,the mediating variable were body composition?body mass index,percentage of body fat,waist-Hip ratio and skeletal muscle mass?,perceived fitness?perceived body fat,perceived body strength and perceived physical endurance?and exercise self-efficacy?aerobic self-efficacy and strength self-efficacy?.First,aerobic fitness was assessed by VO₂max,and muscular strength was assessed by 1 repetition maximum?1-RM?tests.Then,energy consumption during exercise and excess post-exercise oxygen consumption was assessed.Then,participants in 8-week aerobic exercise condition performed a 30 min moderate intensity?65-75%VO₂max?,and participants in 8-week strength training condition performed a 30 min moderate intensity?65-75%1-RM?.Training consisted of a 5 min warm up and a 5 min cool down,3 days/week.The most important thing is to make sure the volumes of exercise?i.e.,kcal expended?were equal.The mediating and dependent variables were assessed at baseline,week 2,week 4,week 6,and week8.Results:1)The Repeated Measures results for each independent variable and mediating variable were presented.For the body satisfaction,a significant main effect for time[F?4,46?=131.153,p<.001,partial?²=.919]indicated increases in body satisfaction across both conditions.The main effect at the type of exercise was not significant[F?1,49?=.087,p>.05,partial?²=.002],and the main effect at the gender was not significant[F?1,49?=1.750,p>.05,partial?²=.034],the interaction was not significant.For social physique anxiety,the main effect at the time point of measurement was significant[F?4,46?=14.017,p<.001,partial?²=.549],the main effect at the type of exercise was not significant[F?4,46?=14.017,p<.001,partial?²=.549],and the main effect at the gender was significant[F?1,49?=5.462,p<.05,partial?²=.100],the interaction was not significant.The results showed that8 weeks of physical exercise could reduce negative body image,there was no difference between the intervention effect of aerobic exercise and strength training,there was no difference between the effect of male and female.2)Bivariate correlations between changes in negative body image and changes in the mediating variables were shown,all significant variables were entered into the regression equation.For all study participants,baseline to week 2:changes in perceived body fat[?=-.435,t=-3.657,p=.001]and perceived strength[?=.293,t=2.461,p=.017]were significant predictors of change in body satisfaction scores.Week 2 to week 4:changes in perceived body fat[?=-.506,t=-4.469,p=.000]and perceived strength[?=.288,t=2.544,p=.014]were significant predictors of change in body satisfaction scores.Week 4 to week 6:change in percentage of body fat[?=-.575,t=-4.486,p=.000]was significant predictor of change in body satisfaction scores.Week 6 to week 8:change in percentage of body fat[?=-.657,t=-6.230,p=.000]was significant predictor of change in body satisfaction scores.The results showed that,in the early period of physical exercise intervention,the change of perceived fitness was the mechanism of physical exercise reducing negative body image,and in the later period of intervention,the change of objective body composition was the mechanism of physical exercise reducing negative body image.Conclusion:Physical exercise can first improve the perceived physical fitness of the sedentary group,and then reduce the negative body image of the group by improving the body composition.When the volumes of exercise were equal,there was no difference between the intervention effect of aerobic exercise and strength training.