title: What intensity of physical activity do previously sedentary middle-aged women select? Evidence of a coherent pattern from physiological, perceptual, and affective markers.
abstract: BACKGROUND
  The intensity of physical activity has been found to be inversely related to adherence, thus contributing to the problem of physical inactivity. Although most physical activity is unsupervised and participants, therefore, self-select the intensity, very little is known about the level of intensity that they select. We hypothesized that participants would select, on average, an intensity proximal to the level of transition from aerobic to anaerobic metabolism.
  
  
  METHODS
  Twenty-three middle-aged, formerly sedentary women participated in (a) an incremental treadmill test to determine their maximal aerobic capacity and gas exchange ventilatory threshold, an index of the aerobic-anaerobic transition, and (b) a 20-min bout of treadmill exercise during which they were allowed to select the speed.
  
  
  RESULTS
  On average, but with considerable interindividual variability, the women selected an intensity that, in terms of treadmill speed, heart rate, oxygen uptake, and perceived exertion was no different from the intensity corresponding to their gas exchange ventilatory threshold. Moreover, affective valence remained positive and stable.
  
  
  CONCLUSIONS
  On average, middle-aged, formerly sedentary women selected an intensity that is considered physiologically effective and reported that it did not feel hard or unpleasant. Future research should examine the sources of interindividual variability and the consequences of exercising at an intensity that exceeds one's preferred level.
authors.affiliation: Department of Health and Human Performance, Iowa State University, Ames, IA 50011, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Lind
authors.forename: Roxane R
authors.initials: RR
authors.lastname: Joens-Matre
authors.forename: Panteleimon
authors.initials: P
authors.lastname: Ekkekakis
mesh_terms: D000328:Adult; D015992:Body Mass Index; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008875:Middle Aged; D010807:Physical Endurance / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012132:Respiratory Muscles / Q000502:physiology
chemical_list: D019344:Lactic Acid