Predicting the rate of oxygen uptake from step counts using ActiGraph waist-worn accelerometers in adults with Down syndrome

Accelerometer-based estimation of oxygen uptake in adults with Down syndrome: vector magnitude vs. vertical axis

BACKGROUND

Triaxial accelerometer output [vector magnitude (VM) counts] may better estimate physical activity intensity as reflected in the rate of oxygen uptake (V̇O₂ ) than the traditional vertical axis (VA) counts in adults with Down syndrome (DS). This study examined the accuracy of VM vs. VA counts in estimating V̇O₂ in adults with and without DS across different physical activities and sedentary behaviours.

METHODS

Sixteen adults with DS (10 men and 6 women; 31 ± 15 years) and 19 adults without DS (10 men and 9 women; 24 ± 5 years) performed 12 tasks. V̇O₂ was measured by portable spirometer (K4b² , Cosmed) and VM and VA with an accelerometer (wGT3X-BT, Actigraph).

RESULTS

Vector magnitude and VA were significant predictors of V̇O₂ in adults with DS (P < 0.001; R²  = 0.74 and 0.65, respectively) and adults without DS (P < 0.001; P < 0.001; R²  = 0.75 and 0.61, respectively). Absolute error of prediction was significantly smaller for VM than VA for sitting, playing app, drawing, sweeping, standing and basketball (P ≤ 0.005), but smaller for VA than VM for walking at 0.8 m·s^-1 (P = 0.005). Bland-Altman plots for adults with and without DS indicated narrower limits of agreement for VM than VA (-5.57 to 5.57 and -6.44 to 6.44 mL·kg^-1 ·min^-1 ; -6.21 to 6.17 and -7.75 to 7.74 mL·kg^-1 ·min^-1 , respectively).

CONCLUSIONS

Vector magnitude and VA are significant predictors of V̇O₂ in adults with and without DS, yet VM more accurately estimated V̇O₂ than VA for most tasks. Development of accelerometer-based prediction of physical activity levels in adults with and without DS may improve by utilising VM counts.

Brief report: Caregiver perceived physical activity preferences of adults with Down syndrome

BACKGROUND

Adults with Down syndrome commonly have low levels of physical activity and face social barriers to engaging in physical activity, including boredom and companionship concerns. Adults with Down syndrome are at increased risk for several co-occurring medial conditions known to benefit from physical activity, including obesity and dementia.

METHOD

This study surveyed 140 caregivers of adults with Down syndrome to determine the physical activity preferences of their adult with Down syndrome.

RESULTS

Dancing was the most frequently caregiver-reported physical activity preference for adults with Down syndrome, followed by walking and active video gaming. Rowing, using an elliptical machine, and jogging were the least preferred activities. Most caregivers reported that their adult with Down syndrome has a companion available for physical activity.

CONCLUSION

Promoting dance in adults with Down syndrome, a caregiver-reported preferred form of physical activity, may help improve physical activity levels and decrease sedentary behaviours in this population.