title: Long-term effects of varying intensities and formats of physical activity on participation rates, fitness, and lipoproteins in men and women aged 50 to 65 years.
abstract: BACKGROUND
  Although exercise parameters such as intensity and format have been shown to influence exercise participation rates and physiological outcomes in the short term, few data are available evaluating their longer-term effects. The study objective was to determine the 2-year effects of differing intensities and formats of endurance exercise on exercise participation rates, fitness, and plasma HDL cholesterol levels among healthy older adults.
  
  
  RESULTS
  Higher-intensity, group-based exercise training; higher-intensity, home-based exercise; and lower-intensity, home-based exercise were compared in a 2-year randomized trial. Participants were 149 men and 120 postmenopausal women 50 to 65 years of age who were sedentary and free of cardiovascular disease. Recruitment was achieved through a random digit-dial community telephone survey and media promotion. All exercise occurred in community settings. For higher-intensity exercise training, three 40-minute endurance training sessions per week were prescribed at 73% to 88% of peak treadmill heart rate. For lower-intensity exercise, five 30-minute endurance training sessions per week were prescribed at 60% to 73% of peak treadmill heart rate. Treadmill exercise performance, lipoprotein levels and other heart disease risk factors, and exercise adherence were evaluated at baseline and across the 2-year period. Treadmill exercise test performance improved for all three training conditions during year 1 and was successfully maintained during year 2, particularly for subjects in the higher-intensity, home-based condition. Subjects in that condition also showed the greatest year 2 exercise adherence rates (P < .003). Although no significant increases in HDL cholesterol were observed during year 1, by the end of year 2 subjects in the two home-based training conditions showed small but significant HDL cholesterol increases over baseline (P < .01). The increases were particularly pronounced for subjects in the lower-intensity condition, whose exercise prescription required more frequent exercise sessions per week. For all exercise conditions, increases in HDL cholesterol were associated with decreases in waist-to-hip ratio in both men and women (P < .04).
  
  
  CONCLUSIONS
  While older adults can benefit from initiating a regular regimen of moderate-intensity exercise in terms of improved fitness levels and small improvements in HDL cholesterol levels, the time frame needed to achieve HDL cholesterol change (2 years) may be longer than that reported previously for younger populations. Frequency of participation may be particularly important for achieving such changes. Supervised home-based exercise regimens represent a safe, attractive alternative for achieving sustained participation.
authors.affiliation: Department of Health Research and Policy, Stanford University School of Medicine, Palo Alto, Calif, USA.
authors.forename: A C
authors.initials: AC
authors.lastname: King
authors.forename: W L
authors.initials: WL
authors.lastname: Haskell
authors.forename: D R
authors.initials: DR
authors.lastname: Young
authors.forename: R K
authors.initials: RK
authors.lastname: Oka
authors.forename: M L
authors.initials: ML
authors.lastname: Stefanick
mesh_terms: D000368:Aged; D008076:Cholesterol, HDL / Q000097:blood; D005080:Exercise Test; D005260:Female; D006321:Heart / Q000502:physiology; D006801:Humans; D008055:Lipids / Q000097:blood; D008074:Lipoproteins / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D010101:Oxygen Consumption; D010806:Physical Education and Training; D005082:Physical Exertion; D010809:Physical Fitness; D012143:Respiratory Physiological Phenomena; D013997:Time Factors
chemical_list: D008076:Cholesterol, HDL; D008055:Lipids; D008074:Lipoproteins