Predicting METs from the heart rate index in persons with Down syndrome.
Use HRindex 1.32 for moderate and 1.80 for vigorous activity when prescribing exercise for adults with Down syndrome.
01Research in Context
What this study did
The team asked adults with Down syndrome to walk and jog on a treadmill.
They tracked heart rate and measured oxygen use at the same time.
The goal was to find the heart-rate index numbers that match light, moderate, and hard exercise.
What they found
Adults with Down syndrome need higher heart-rate index values than typical adults to reach the same calorie-burn level.
Moderate work starts at 1.32 and vigorous work starts at 1.80.
Using the usual tables would label their effort too low.
How this fits with other research
Agiovlasitis et al. (2025) later showed that percent VO2Reserve predicts effort even better than METs in the same group.
Castañe et al. (1993) already proved that standard ACSM equations wildly over-estimate fitness in Down syndrome, so custom cut-offs like these were needed.
Nickerson et al. (2015) also found that the Body Adiposity Index fails in this population, repeating the theme that one-size formulas do not fit Down syndrome.
Why it matters
When you write exercise plans, plug 1.32 and 1.80 into your heart-rate checks instead of the textbook numbers.
This small switch keeps workouts safe, motivating, and truly moderate or vigorous for your adult clients with Down syndrome.
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02At a glance
03Original 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.
Research in developmental disabilities, 2014 · doi:10.1016/j.ridd.2014.06.005