title: Using threshold messages to promote physical activity: implications for public perceptions of health effects.
abstract: BACKGROUND
  The promotion of physical activity (PA) guidelines to the general public is an important issue that lacks empirical investigation. PA campaigns often feature participation thresholds that cite PA guidelines verbatim [e.g., 150 min/week moderate-to-vigorous physical activity (MVPA)]. Some campaigns instead prefer to use generic PA messages (e.g., do as much MVPA as possible). 'Thresholds' may disrupt understanding of the health benefits of modest PA participation. This study examined the perception of health benefits of PA after exposure to PA messages that did and did not contain a duration threshold.
  
  
  METHODS
  Brief structured interviews were conducted with a convenience sample of adults (n = 1100). Participants received a threshold message (150 min/week MVPA), a message that presented the threshold as a minimum; a generic message or no message. Participants rated perceived health effects of seven PA durations. One-way analyses of variance with post hoc tests for group differences were used to assess raw perception ratings for each duration of PA.
  
  
  RESULTS
  Recipients of all three messages held more positive perceptions of >150 min/week of MVPA relative to those not receiving any message. For MVPA durations <150 min/week, the generic PA message group perceived the greatest health benefits. Those receiving the threshold message tended to have the least positive perceptions of durations <150 min/week.
  
  
  CONCLUSIONS
  Threshold messages were associated with lower perceived health benefits for modest PA durations. Campaigns based on threshold messages may be limited when promoting small PA increases at a population level.
authors.affiliation: 1 School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK.
authors.forename: Emily C L
authors.initials: EC
authors.lastname: Knox
authors.forename: Oliver J
authors.initials: OJ
authors.lastname: Webb
authors.forename: Dale W
authors.initials: DW
authors.lastname: Esliger
authors.forename: Stuart J H
authors.initials: SJ
authors.lastname: Biddle
authors.forename: Lauren B
authors.initials: LB
authors.lastname: Sherar
mesh_terms: D000328:Adult; D000368:Aged; D017408:Guidelines as Topic; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D007407:Interviews as Topic; D008875:Middle Aged; D009043:Motor Activity; D010465:Perception; D011634:Public Health; D006113:United Kingdom