Feasibility of social cognitive theory-based fall prevention intervention for people with intellectual disabilities living in group-home.

BACKGROUND: Adults with intellectual disability (ID) have a higher rate of fall events than the general population. Consequently, interventions for reducing fall events and improving health are highly required for individuals with ID. One essential step towards effectively delivering fall prevention interventions among adults with ID involves evaluating their feasibility. This study examined the feasibility of a home-based exercise intervention, supplemented with behavioural change strategies, among individuals with ID living in residential settings. METHOD: This study provided an 8-week intervention, consisting of a workshop for support workers and sessions for participants with ID, focusing on behavioural reward/s, education regarding fall prevention/exercise and exercise training. One week prior to and 1 week following such an intervention, such participants underwent measurements for (1) physical performance, (2) fall efficacy, (3) self-efficacy for activity and (4) social support. RESULTS: Participants having ID (n = 33), support workers (n = 11) and one administrator participated in this study. There were no adverse events during the intervention, and the mean adherence rate was 70.8 ± 19.5%. Two participants with ID dropped out of the programme due to a lack of interest. The participants with ID significantly improved individual physical performance, self-efficacy for activity, fall efficacy and support from friends and support workers. CONCLUSIONS: Fall prevention interventions for adults with ID living in group-homes were highly promising for eventual large-scale implementation within such communities.

Calibration of hip accelerometers for measuring physical activity and sedentary behaviours in adults with Down syndrome.

BACKGROUND: The knowledge base on physical activity and sedentary behaviour in adults with Down syndrome (DS) may advance by accelerometer calibration studies. This study aimed to develop cut-points for sedentary behaviour and moderate-to-vigorous physical activity (MVPA) for adults with DS based on output from accelerometers worn on the dominant and non-dominant hips. METHODS: Sixteen adults with DS (10 men; age 31 ± 15 years) performed 12 tasks including sedentary behaviours and physical activities. We obtained metabolic equivalents (METs) with indirect calorimetry and vector magnitude (VM) output from triaxial accelerometers (wGT3X-BT, ActiGraph) worn on the dominant and non-dominant hips. Receiver operating characteristic curves were used to identify optimal VM cut-points that maximised sensitivity and specificity. RESULTS: Overall classification accuracy was very high (area under the ROC curve: 0.95 and 0.92 for sedentary and MVPA models, respectively). For the non-dominant hip, the optimal VM cut-points were (1) sedentary behaviour ≤236 counts·min-1 and (2) MVPA ≥2167 counts·min-1 . For the dominant hip, optimal cut-points were (1) sedentary behaviour ≤243 counts·min-1 and (2) MVPA ≥2092 counts·min-1 . CONCLUSIONS: The presented VM cut-points for sedentary behaviour and MVPA for adults with DS had high classification accuracy. There were small differences in accelerometer cut-points between the dominant and non-dominant hip.

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.

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

BACKGROUND: Step rate predicts ambulatory intensity as reflected in the rate of oxygen uptake (VO2 ) - a measure of energy expenditure. Whether step rate as measured by an accelerometer predicts VO2 in adults with Down syndrome (DS) is unknown. We examined whether step rate predicts VO2 in adults with and without DS. We also developed an equation for predicting VO2 and examined its accuracy. METHOD: Sixteen adults with DS (6 women and 10 men; age 31 ± 15 years) and 19 adults without DS (9 women and 10 men; age 25 ± 6 years) performed standing and walking at their preferred speed, 0.8 and 1.4 m·s-1 . We measured VO2 with a portable spirometer and step rate with a triaxial accelerometer (wGT3X-BT; ActiGraph) on the non-dominant hip, using the low-frequency extension filter. We ran multilevel regression for predicting VO2 from linear and quadratic terms for step rate, group (1 = DS; 0 = non-DS), body mass, height, body mass index (BMI), leg length and sex. We estimated VO2 with the resultant equation and calculated the equation's absolute per cent error, which we compared between groups. RESULTS: VO2 was higher in persons with than without DS only at the fast walking speed (P = 0.018). DS did not predict VO2 . Step rate, step rate squared and BMI were significant predictors of VO2 (P < 0.001; R2  = 0.80). Absolute error across walking speeds was 13.5-18.8% and 11.7-13.4% for adults with and without DS, respectively, and did not differ between groups or speeds. CONCLUSIONS: Step rate, step rate squared and BMI predict VO2 in adults with and without DS. Prediction error does not differ between groups.

Step-counting accuracy of activity monitors in persons with Down syndrome.

BACKGROUND: Accelerometers and pedometers have been used to monitor the number of steps. However, the evidence on the step-counting accuracy of these devices - especially accelerometers - is limited in persons with Down syndrome (DS). This study therefore examined the accuracy of accelerometers placed on the hip or wrist and of a pedometer with a uni-axial accelerometer mechanism in measuring steps in persons with DS and whether device error is associated with walking speed, height, weight, body mass index, waist circumference, leg length, age or sex. METHOD: Seventeen persons with DS (eight women and nine men; age 33 ± 15 years) walked over-ground for 6 min at their preferred speed. The steps were measured with a hip-worn and a wrist-worn ActiGraph accelerometer using the manufacturer's default (DF) and low-frequency extension (LFE) filters, and with the NL-1000 New Lifestyles pedometer on the hip. Steps were also measured with hand tally which served as the criterion. RESULTS: Absolute percent error was considerable and differed statistically between devices (P = 0.001); however, error improved for accelerometers when LFE was applied (Hip-DF: 31.6 ± 18.8%; Hip-LFE: 9.7 ± 12.8%; Wrist-DF: 32.7 ± 14.2%; Wrist-LFE: 13.6 ± 10.2%; Pedometer: 23.2 ± 22.8%). Bland-Altman plots indicated underestimation of steps for accelerometers and the pedometer. Application of LFE, however, improved the prediction of the accelerometers. The number of steps measured by the hip accelerometer with LFE and by the pedometer did not differ statistically from actual steps. Steps by the remaining methods were significantly lower than hand tally (P ≤ 0.001). Correlations between percent error for each device and walking speed, anthropometry, age or sex ranged between -0.28 and +0.48, and were non-significant, except for age. CONCLUSIONS: The results demonstrated that the pedometer and ActiGraph accelerometers have considerable error in measuring steps of persons with DS. Application of LFE, however, significantly improved the step-counting performance of the Actigraph accelerometers.

Resting and post exercise arterial-ventricular coupling in endurance-trained men and women.

The relationship between effective arterial elastance (EA) and left ventricular end-systolic elastance (ELV) is a determinant of cardiac performance, known as arterial-ventricular coupling (AVC). The purpose of this study was to examine the acute effects of high-intensity interval (HI) and low-intensity steady state (SS) exercise on AVC. Twenty-three (13 men, 10 women) young (26 years), endurance-trained individuals completed a VO2 peak test followed by an acute SS and HI exercise bout on separate visits. Before (Pre) and 30- and 60-min after each bout, measures of aortic end-systolic pressure (ESP), left ventricular end-systolic volume and stroke volume were obtained. Across both conditions (HI and SS) and both sexes, at 30 and 60 min post exercise, ESP and ELV were reduced from Pre 30 and 60-min exercise (ESP: 86±7, 77±8 and 73±8 mm Hg; ELV: 4.93±1.53, 4.19±1.38 and 4.10±1.53 mm Hg ml(-1) m(-2)). EA was only reduced at 60 min post exercise (1.90±0.36, 1.78±0.50 and 1.57±0.36). Both EA and ELV were reduced following acute SS and HI exercise. This is likely because of similar reductions in total peripheral resistance following both exercise bouts. These results suggest that endurance-trained individuals are able to match peripheral vascular changes with changes in left ventricular function following dynamic exercise of different intensities.

Comparison of the acute impact of maximal arm and leg aerobic exercise on arterial stiffness.

Acute aerobic exercise decreases arterial stiffness based on the intensity of the exercise and the arterial segment studied. Arm exercise may differentially affect arterial stiffness compared to leg exercise but this has not been studied. We hypothesized that maximal aerobic exercise would reduce local peripheral pulse wave velocity i.e. femoral-dorsalis pedis (LPWV) following leg exercise and carotid-radial (APWV) following arm exercise without any crossover effect. The main purpose of the study is to compare the effects of maximal arm versus leg aerobic exercise on peripheral and central arterial stiffness. Fifteen healthy participants (9 males and 6 females, 25 ± 5 years) performed maximal arm-ergometer and leg-ergometer exercise in a randomized, crossover design. Peripheral and central pulse wave velocities (PWV) were obtained using applanation tonometry before and 10 min after each maximal exercise bout. 2 × 2 repeated measures analysis of variance was used to detect differences between conditions. There was a significant interaction in the APWV between the two exercise modes. However, there was no condition or interaction effect on LPWV following maximal arm versus leg exercise. There was no significant difference in central PWV between conditions or with time. There was no change in MAP (75 ± 6-77 ± 3) after maximal arm exercise as compared to the maximal leg exercise (73 ± 6-80 ± 2). Arm exercise produced a more generalized effect on arterial stiffness than leg exercise. The prescription of upper limb exercise may be considered for purposes of eliciting post-exercise systemic changes in arterial stiffness.