title: Predicting METs from the heart rate index in persons with Down syndrome.
abstract: Persons with Down syndrome (DS) have altered heart rate modulation and very low aerobic fitness. These attributes may impact the relationship between metabolic equivalent units (METs) and the heart rate index (HRindex-the ratio between heart rate during activity and resting heart rate), thereby altering the HRindex thresholds for moderate- and vigorous-intensity physical activity. This study examined whether the relationship between METs and HRindex differs between persons with and without DS and attempted to develop thresholds for activity intensity based on the HRindex for persons with DS. METs were measured with portable spirometry and heart rate with a monitor in 18 persons with DS (25 ± 7 years; 10 women) and 18 persons without DS (26 ± 5 years; 10 women) during 6 over-ground walking trials, each lasting 6min, at the preferred walking speed and at 0.5, 0.75, 1.0, 1.25, and 1.5m/s. The relationship between METs and HRindex in the two groups was analyzed with multi-level modeling with random intercepts and slopes. Group, HRindex, and the square of HRindex were significant predictors of METs (p<0.001; R(2)=0.65). Absolute percent error did not differ significantly between groups across speeds (DS: 19.6 ± 14.4%; non-DS: 21.0 ± 14.5%). Bland-Altman plots demonstrated somewhat greater variability in the difference between actual and predicted METs in participants with than without DS. The HRindex threshold for moderate-intensity activity was 1.32 and 1.20 for persons with and without DS, respectively. The HRindex threshold for vigorous-intensity activity was 1.80 and 1.65 for persons with and without DS, respectively. Persons with DS have an altered relationship between METs and HRindex and higher HRindex thresholds for moderate- and vigorous-intensity physical activity.
authors: Department of Kinesiology, Mississippi State University, 233 McCarthy Gym, P.O. Box 6186, Mississippi State, MS 39762, United States. Electronic address: sagiovlasitis@colled.msstate.edu.
authors: Stamatis
authors: S
authors: Agiovlasitis
authors: Department of Exercise and Sports Science, Fitchburg State University, 155 North Street, Fitchburg, MA 01420, United States.
authors: Lindy M
authors: LM
authors: Rossow
authors: Department of Kinesiology, East Carolina University, Greenville, NC 27858, United States.
authors: Huimin
authors: H
authors: Yan
authors: Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, United States.
authors: Sushant M
authors: SM
authors: Ranadive
authors: Department of Exercise and Sports Science, Fitchburg State University, 155 North Street, Fitchburg, MA 01420, United States.
authors: Christopher A
authors: CA
authors: Fahs
authors: Department of Kinesiology & Community Health, University of Illinois at Urbana-Champaign, 906 S Goodwin Avenue, Urbana, IL 61801, United States.
authors: Robert W
authors: RW
authors: Motl
authors: College of Applied Health Sciences, University of Illinois at Chicago, 808 S. Wood Street, MC 518, Chicago, IL 60612, United States.
authors: Bo
authors: B
authors: Fernhall
mesh_terms: D000293:Adolescent; D000328:Adult; D004314:Down Syndrome / Q000503:physiopathology*; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D055686:Metabolic Equivalent / Q000502:physiology*; D055815:Young Adult
keywords: Down syndrome; Energy expenditure; Heart rate; Physical activity assessment