Dose-response Relationship Between Defined Exercise And Cardiorespiratory Fitness In40-49yr Men

Purpose:Through analyze the associations of CRF and PA with MS morbidity and risk factors from sedentary to very vigorous levels of PA in health adult men through cross-sectional investigation and intervention. The paper was to discuss the effect of cardiorespiratory fitness on MS risk factors. Moreover, this study was to determine whether exercise prescriptions differing in volume or intensity also differ in their CRF and MS risk factors after12weeks training, and investigate the mechanisms for in-creases in V02peak with different dose. The research altogether divides into three parts as follow:Part1:the associations of CRF and PA with MS morbidity and risk factorsMethods:This cross-sectional study included246adult men aged40-49years. PA was assessed with an International Physical Activity Questionnaire (IPAQ), including PA volume (PAv), intensity (PAi) and PA duration (PAd), CRF indexed by peak oxy-gen uptake(V02peak) was assessed by using respiratory gas exchange in a cycle max-imal ergometer exercise test. The clustering of MS risk factors, including blood pres-sure, fasting glucose, fasting triglycerides, lipoprotein cholesterol and waist-hip ratio were determined. Results:CRF was inversely associated with MS risk fac-tors (r=0.19, P<0.05), the odd ratios between BMI, SBP, TG, HDL-C, FBP and low levels of CRF reduces by0.337-0.873, which show the dose-response relationship between CRF and MS morbidity and risk factors.Part2:Effect of different dose of exercise volume and intensity on V02max and MS risk factors.Methods:A total of58sedentary subjects aged40-49yr were assigned to participate for12weeks in a control group or in one of three exercise groups:1) low vo-lume/moderate intensity (LVMI, equivalent of1200kcal/wk at40-55%V02peak,2) low volume/vigorous intensity (LVVI, 1200kcal/wk at65-80%V02peak) and3) high vo-lume/vigorous intensity (HVVI,2000kcal/wk at65-80%VO2peak). Participants were instructed to not change their usual diet throughout the study. The47subjects who complied with these guidelines served as the basis for the main analysis. V02peak and time to exhaustion (TTE) were tested before and after12weeks training. Results:All exercise groups increased V02peak and TTE compared to the baseline. V02peak increased significantly(p<0.05) in both LVVI (29.33±3.4ml/kg/min vs33.97±3.7ml/kg/min) and HVVI (30.71±4.7ml/kg/min vs36.11±5.6ml/kg/min) groups,15.8%and17.6%respectively; the LVVI resulted in greater improvement than the LVMI(27.91±4.9vs29.02±3.0)1ml/kg/min(4%). It seems that V02peak is respond to intensity not volume. Moreover, SBP, DBP, TG, HDL-C and LDL-C also respond to intensity and volume, but HVVI would obtain most benefits.Part3:The mechanisms of different dose of exercise volume and intensity on cardiorespiratory fitnessMethods:the subjects and exercise protocols like the part2. Maximal cardiac output (Q) and stroke volume (SV) were measured using echocardiography, maximal arteri-al-venous02difference (a-v02diff) was calculated from the equation:a-v02diff(ml02/100ml blood)=V02(L/min)/Q(L/min) X100. Results:1) Both of intensity and vo-lume not only improve RBC, Hb and baPWV, which shows significantly only in high volume/vigorous intensity group, but also Tei index. There are different between low volume/moderate intensity and low volume/vigorous intensity groups to ESV, EF and FS, such as systole responds to intensity, diastole only responds to high volume.2) Maximal a-v02diff increased in all exercise groups, but a-v02diff and SV only enhance in the two vigorous groups, which also improving significantly in high vo-lume/vigorous intensity group.Conclusion:(1) Cardiorespiratory fitness not only matters more than physical activity to predict MS cardiovascular risk factors in healthy men, but also was the independent predictor of CRF. High level of Cardiorespiratory fitness would obtain more benefits, and show dose-response with MS morbidity and risk factors.2) Intensity is the main factor for improving V02max than volume.3) Both of volume and intensity would improve lipids and blood pressure, and high volume/vigorous intensity would obtain more benefits.4) Cardiac function and a-v02diff are main factors for increasing V02max. Although it is same for low volume/vigorous intensity and high vo-lume/vigorous intensity to increase V02max, the mechanisms are different. V02max increased in high volume/vigorous intensity not only caused by Cardiac function and a-v02diff, but peripheral mechanisms such as RBC, Hb, baPWV.