title: Step-rate thresholds for moderate and vigorous-intensity activity in persons with Down syndrome.
abstract: OBJECTIVE
  Monitoring physical activity intensity in persons with Down syndrome (DS) may be affected by an altered relationship between metabolic equivalent units (METs) and step-rate. This study examined whether the relationship between METs and step-rate is altered in persons with DS and developed step-rate thresholds for activity intensity for these persons.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  Eighteen persons with DS (25±7years; 8 women) and 22 persons without DS (26±5 years; 9 women) completed six over-ground walking trials each lasting 6 min at their preferred speed and at 0.5, 0.75, 1.0, 1.25, and 1.5 ms⁻¹. METs were measured with portable spirometry and step-rate with hand-tally. Random effects models were used to predict METs from step-rate, squared step-rate, height, presence of DS, sex, and body mass index (BMI).
  
  
  RESULTS
  Step-rate, squared step-rate, height, and presence of DS contributed significantly to the model (SE=0.20 METs; R²=0.63); sex and BMI did not contribute. As height increased, step-rate thresholds for moderate and vigorous-intensity activity decreased. For a given height, participants with DS had lower step-rate at the moderate-intensity threshold than participants without DS. Across participant heights, the moderate-intensity cut-off ranged between 101 and 76 steps min⁻¹ in persons with DS and between 103 and 80 steps min⁻¹ in persons without DS. For persons with DS, step-rate at the vigorous-intensity threshold ranged between 136 and 126 steps min⁻¹.
  
  
  CONCLUSIONS
  Persons with DS showed altered relationship between METs and step-rate and had lower step-rate thresholds for moderate-intensity activity than persons without DS.
authors.affiliation: Department of Kinesiology, Mississippi State University, MS, USA. sagiovlasitis@colled.msstate.edu
authors.forename: Stamatis
authors.initials: S
authors.lastname: Agiovlasitis
authors.forename: Michael W
authors.initials: MW
authors.lastname: Beets
authors.forename: Robert W
authors.initials: RW
authors.lastname: Motl
authors.forename: Bo
authors.initials: B
authors.lastname: Fernhall
mesh_terms: D000328:Adult; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D004314:Down Syndrome / Q000503:physiopathology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D055686:Metabolic Equivalent; D018670:Monitoring, Ambulatory; D013147:Spirometry; D016138:Walking / Q000502:physiology; D055815:Young Adult