title: Effects of Exercise Training on Cardiorespiratory Fitness and Biomarkers of Cardiometabolic Health: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.
abstract: BACKGROUND
  Guidelines recommend exercise for cardiovascular health, although evidence from trials linking exercise to cardiovascular health through intermediate biomarkers remains inconsistent. We performed a meta-analysis of randomized controlled trials to quantify the impact of exercise on cardiorespiratory fitness and a variety of conventional and novel cardiometabolic biomarkers in adults without cardiovascular disease.
  
  
  RESULTS
  Two researchers selected 160 randomized controlled trials (7487 participants) based on literature searches of Medline, Embase, and Cochrane Central (January 1965 to March 2014). Data were extracted using a standardized protocol. A random-effects meta-analysis and systematic review was conducted to evaluate the effects of exercise interventions on cardiorespiratory fitness and circulating biomarkers. Exercise significantly raised absolute and relative cardiorespiratory fitness. Lipid profiles were improved in exercise groups, with lower levels of triglycerides and higher levels of high-density lipoprotein cholesterol and apolipoprotein A1. Lower levels of fasting insulin, homeostatic model assessment-insulin resistance, and glycosylated hemoglobin A1c were found in exercise groups. Compared with controls, exercise groups had higher levels of interleukin-18 and lower levels of leptin, fibrinogen, and angiotensin II. In addition, we found that the exercise effects were modified by age, sex, and health status such that people aged <50 years, men, and people with type 2 diabetes, hypertension, dyslipidemia, or metabolic syndrome appeared to benefit more.
  
  
  CONCLUSIONS
  This meta-analysis showed that exercise significantly improved cardiorespiratory fitness and some cardiometabolic biomarkers. The effects of exercise were modified by age, sex, and health status. Findings from this study have significant implications for future design of targeted lifestyle interventions.
authors.affiliation: Department of Epidemiology, School of Public Health, Brown University, Providence, RI (X.L., W.C.W., S.L.).
authors.forename: Xiaochen
authors.initials: X
authors.lastname: Lin
authors.affiliation: Department of Epidemiology, Richard M. Fairbanks School of Public Health, Indiana University, Indianapolis, IN (X.Z., Y.S.).
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Center for the Youth Sport Research and Development, China Institute of Sport Science, Beijing, China (J.G.).
authors.forename: Jianjun
authors.initials: J
authors.lastname: Guo
authors.affiliation: Geriatrics, Research, Education and Clinical Centers, VA Greater Los Angeles Healthcare System, Los Angeles, CA (C.K.R.).
authors.forename: Christian K
authors.initials: CK
authors.lastname: Roberts
authors.affiliation: Department of Kinesiology, Center for Physical Activity in Wellness and Prevention, Indiana University-Purdue University at Indianapolis, IN (S.M.K.).
authors.forename: Steve
authors.initials: S
authors.lastname: McKenzie
authors.affiliation: Department of Epidemiology, School of Public Health, Brown University, Providence, RI (X.L., W.C.W., S.L.) Division of Cardiology and Veterans Affairs Medical Center, Department of Medicine, Alpert Medical School, Brown University, Providence, RI (W.C.W., S.L.).
authors.forename: Wen-Chih
authors.initials: WC
authors.lastname: Wu
authors.affiliation: Department of Epidemiology, School of Public Health, Brown University, Providence, RI (X.L., W.C.W., S.L.) Division of Cardiology and Veterans Affairs Medical Center, Department of Medicine, Alpert Medical School, Brown University, Providence, RI (W.C.W., S.L.) Division of Endocrinology, Department of Medicine, Rhode Island Hospital, Providence, RI (S.L.).
authors.forename: Simin
authors.initials: S
authors.lastname: Liu
authors.affiliation: Department of Epidemiology, Richard M. Fairbanks School of Public Health, Indiana University, Indianapolis, IN (X.Z., Y.S.).
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Song
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood*; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*; D015444:Exercise; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D010809:Physical Fitness; D011379:Prognosis; D065840:Protective Factors; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D012307:Risk Factors; D040242:Risk Reduction Behavior; D012737:Sex Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers
keywords: biomarker; cardiometabolic health; cardiovascular disease prevention; exercise training