Effects Of Physical Activity And Cardiorespiratory Fitness On Resting Metabolic Rate

Objective:This dissertation consists of two studies that designed to 1) identify effects of exercise program on resting metabolic rate (RMR); 2) Explore the cross-sectional associations and longitudinal effects of habitual physical activity (PA) and cardiorespiratory fitness (CRF) with RMR in young adults followed for 15months.Methods:1. The controlled trials of exercise for RMR in adults were identified from English and Chinese literature database. Meta-analysis was performed via Review Manager 5.3 software.2. In the Energy Balance Study,418 young adults received examinations included RMR, body composition time spent in different intensity of PA and energy expenditure, CRF, and energy intake.Results:1. The pooled result showed that exercises were benefit to increase RMR in adults (SMD=0.14,95%CI:0.06,0.23, P<0.01); In different exercise type subgroups, resistant exercise increased RMR in adults (SMD=0.24,95%CI:0.09,0.38, P<0.01), aerobic exercise and aerobic combined with resistant exercise have a trend to increase RMR (SMD was 0.04,0.17 respectively) but the effects were not significant. In different control type subgroups, exercise alone increased RMR in adults compared with control group (SMD=0.18,95%CI:0.08,0.29, P<0.01); exercise combined with dietary restriction has a trend to increase RMR (SMD=0.08) but the effect was not significantly different with dietary restriction alone. There was difference effect for RMR between different gender groups. Exercise could significantly improve RMR for male, while there was no difference between different age groups in the same gender.2. Moderate to Vigorous Physical Activity in 10 minute-bout (MVPA-10min bout) was positively correlated with RMR in male and female (r=0.476,0.534 respectively, P<0.01), the correlation still significantly after adjusted fat-free mass (FFM) and fat mass (FM); RMR in physically active group was significantly higher than inactive group in males and females (P<0.01); RMR decreased after MVPA-lOmin bout reduced in male (P<0.01); in the linear mixed model (LMM), change of MVPA-10min bout was positively associated with change of RMR in male and female and the association still significant after adjusted FFM and FM.3. Sedentary time was negatively correlated with RMR in male and female (r=-0.31,-0.382 respectively, P<0.01), the correlation was not significant after adjusted FFM and FM; RMR in longest sedentary time group was significantly lower than shortest group in males and females (P<0.01); RMR did not change significantly after sedentary time increase or decrease; in the LMM, change of sedentary time was negatively associated with change of RMR in male and female, and the association still significant after adjusted FFM and FM only in female.4. VO2max was positively correlated with RMR in male and female (r=0.497,0.607 respectively, P<0.01), the correlation still significantly after adjusted FFM and FM; RMR in high CRF group was significantly higher than low group in males and females (P<0.01); RMR increased 0.33mL/kg/min after CRF improved and decreased 0.19 mL/kg/min after CRF reduced in male; in LMM, change of CRF was positively associated with change of RMR in male and female and the association still significant after adjusted FFM and FM.Conclusions:1. Regularly exercise was benefit to increase RMR in adults and the effect of resistant exercise for improving RMR was the most significant.2.The effect of regularly exercise to increase RMR was more significant in male than in female.3. Increasing MVPA-10min bouts, decreasing sedentary time, and improving CRF were benefit to increase RMR.