Accuracy of a piezoelectric pedometer in persons with and without Down syndrome.

BACKGROUND: Piezoelectric pedometers with a tri-axial accelerometer mechanism may effectively monitor physical activity in persons with Down syndrome (DS), but their accuracy has not been determined in this population. AIM: To examine the accuracy of a pedometer with a tri-axial accelerometer mechanism in measuring steps at different walking speeds in persons with and without DS. METHODS: Eighteen persons with DS (8 women; age 25±7y) and 22 persons without DS (9 women; 26±5y) participated in this study. Participants completed six over-ground walking trials at the preferred speed and at 0.5, 0.75, 1.0, 1.25, and 1.5ms-1, each lasting 6min. The steps taken were measured with hand-tally and with the Walk4Life MVPa piezoelectric pedometer. Pedometer accuracy was assessed with absolute percent error and Bland-Altman plots. RESULTS: Absolute percent error did not differ between persons with and without DS across speeds. Error decreased with increased speed (p<0.001), but leveled off at ≥1.0ms-1. Pedometers underestimated steps at 0.5 and 0.75ms-1, but were highly accurate at the preferred walking speed and at speeds ≥1.0ms-1. CONCLUSIONS: A piezoelectric pedometer with a tri-axial accelerometer mechanism measures steps with high accuracy at the preferred walking speed and at speeds ≥1.0ms-1 in persons with and without DS. Accuracy, however, is compromised at slower speeds. Across speeds, pedometer error is similar between persons with and without DS.

Normal HR with tilt, yet autonomic dysfunction in persons with Down syndrome.

UNLABELLED: Persons with Down syndrome (DS) exhibit altered autonomic function at rest and in response to adrenergic stimuli. It is unknown whether a subset of persons with DS that have similar HR responses to a task would have similar responses in HR variability (HRV). PURPOSE: This study aimed to compare cardiac autonomic function during upright tilt using HRV analysis in persons with and without DS when persons with and without DS were matched for the change in HR. METHODS: Persons with (25 ± 2 yr; 30.4 ± 1.9 kg·m, n = 15) and without DS (27 ± 2 yr; 24.7 ± 1.1 kg·m, n = 15) were matched on their HR response to a 5-min tilt at 80°, whereas a subset of persons with DS (28 ± 3 yr; 33.5 ± 2.0 kg·m, n = 11) were not matched for the change in HR. HRV was assessed in both the frequency (natural log transformation (Ln) of low frequency (LF), high frequency (HF), LF/HF ratio, and total power (TP)) and time domains (root mean square of successive differences [RMSSD]). RESULTS: Changes in HR were similar in DS-matched and control but lower in DS-not matched. Tilt effects were observed for LnHF, LNTP, and RMSSD in all groups (P < 0.05). Both groups of persons with DS exhibited reduction in LnLF, with no change in the control group (P < 0.05). The increase in LF/HF was greater in the group without DS when compared with that in DS-not matched (8.71 ± 2.38 vs 2.34 ± 1.39, P < 0.05) but not when compared with that in DS-matched (3.59 ± 1.10, P = 0.075). CONCLUSIONS: Despite similar HR response to passive upright tilt in the DS-matched, we still observed reduced sympathetic dominance in response to upright tilt in persons with DS.

Impact of obesity and Down syndrome on peak heart rate and aerobic capacity in youth and adults.

Individuals with Down syndrome (DS) exhibit reduced aerobic capacity with reduced peak heart rate (HRpeak). This condition is often coexistent with higher level of obesity compared to individuals without DS. The purpose of this study is to investigate the effects of obesity and Down syndrome (DS) on peak heart rate (HRpeak) and peak oxygen consumption (VO2peak) in children and adults both with and without intellectual disabilities (ID)s. VO2peak and HRpeak from individualized treadmill tests on 654 individuals were analyzed. Body mass index was used to categorize individuals' weight status using standard cut-offs. DS groups had the lowest HRpeak (167bpm±14, p<0.05) compared to individuals with (183bpm±12) without ID (187bpm±12). Obesity did not affect HRpeak among adults and children with DS. VO2peak was lower among individuals with DS (25.2mL/kg/min±6.3, p<0.05) when compared individuals with (37.0mL/kg/min±10.5) and without ID (36.1mL/kg/min±10.4). Obese adults with DS had lower VO2peak (24.3mL/kg/min±6.9, p=0.001) compared to the normal weight (26.7±7.1mL/kg/min) and overweight groups (27.0mL/kg/min±6.1) with DS. Conversely, in children, obesity level did not impact VO2peak in individuals with DS. Our results suggest that DS attenuates both VO2peak and HRpeak, regardless of obesity status and age group. However, obesity was associated with lower VO2peak in all adults, but not in children with DS.

Heart rate complexity in response to upright tilt in persons with Down syndrome.

People with Down syndrome (DS) show altered autonomic response to sympatho-excitation. Cardiac autonomic modulation may be examined with heart rate (HR) complexity which is associated uniquely with cardiovascular risk. This study examined whether the response of HR complexity to passive upright tilt differs between persons with and without DS and whether potential between-group differences in this response are accounted for by differences in body mass index (BMI). The electrocardiogram of 16 persons with DS (8 women, 8 men) and 16 persons without DS (8 women, 8 men) was recorded during 10 min of supine rest and 10 min of upright tilt. For each participant, 550 continuous, steady state, and ectopy-free R-R intervals under each condition were analyzed. Dependent variables were approximate entropy, correlation dimension, StatAv, and the mean R-R interval. In response to tilt, changes in approximate entropy and correlation dimension were reduced in participants with DS (p<0.05). These differences were explained by higher BMI in participants with DS. StatAv increased in persons with DS (p < 0.05) and stayed the same in those without DS even when controlling for BMI. The response of R-R interval did not differ between groups. None of the variables differed between groups at rest. Therefore, people with DS show smaller decrease in HR complexity in response to upright tilt than people without DS partially due to their higher BMI. Resting HR complexity does not differ between persons with and without DS. These results may have implications for cardiovascular risk in people with DS.

Prediction of VO2peak from the 20-m shuttle-run test in youth with Down syndrome.

This study examined whether 20-m shuttle-run performance, sex, body mass index (BMI), age, height, and weight are associated with peak oxygen uptake (VO2peak) in youth with Down syndrome (DS; n = 53; 25 women, age 8-20 years) and whether these variables can be used to develop an equation to predict VO2peak. BMI, 20-m shuttle-run performance, and sex were significantly associated with VO2peak in youth with DS, whereas age, height, and weight were not. A regression model included only shuttle-run performance as a significant predictor of VO2peak; however, the developed prediction equation had low individual predictability. Therefore, 20-m shuttle-run performance alone does not provide valid prediction of VO2peak in youth with DS. Sex, BMI, age, height, and weight do not improve the prediction of VO2peak.

The effect of progressive resistance training on leg strength, aerobic capacity and functional tasks of daily living in persons with Down syndrome.

PURPOSE: The purpose of this study was to examine the effect of progressive resistance training on leg strength, aerobic capacity and physical function in persons with Down syndrome (DS). METHOD: Thirty persons with DS (age 28 SD 8 years) were assigned to an intervention or control group. The intervention group performed resistance training 2 days per week for 10 weeks. Participants performed tests to measure isometric and isokinetic knee extensor and flexor peak torque, peak aerobic capacity and timed performance on chair rise, walking and stair ascent and descent. RESULT: Persons with DS receiving the intervention significantly increased their isokinetic knee extensor and flexor peak torque [Absolute change (post minus pre-value) was 17.0 SD 29.6 and 12.6 SD 18.9 N m, respectively] and isometric knee extensor peak torque at angles of 45° (2.9 SD 23.2 N m), 60° (3.0 SD 22.9 N m) and 75° (14.2 SD 30.0 N m). These changes were significantly greater than in the control group. In addition, the time to ascend (-0.3 SD 0.8 s) and descend (-0.6 SD 0.9 s) stairs significantly decreased in the intervention group compared to the control group. CONCLUSION: These findings show that progressive resistance training is an effective intervention for persons with DS to improve leg strength and stair-climbing ability.

Using pedometers to measure moderate-to-vigorous physical activity for youth with an intellectual disability.

BACKGROUND: Pedometers serve as one of the most feasible and cost-effective methods for frontline practitioners to measure moderate-to-vigorous physical activity (MVPA) of youth with an intellectual disability (YwID) but, historically, pedometers have been unable to measure MVPA. Technological advancements now allow pedometers to measure MVPA via step frequency (steps per minute). Translating the output of this technology into practical information that frontline practitioners and families can use, however, will require accurate step frequency guidelines. OBJECTIVE: The purpose of this study was to identify steps per minute thresholds corresponding to MVPA for YwID. METHODS: Thirty-eight children and adolescents (10 girls, 11.8 ± 1.8 years) attending a summer camp for youth with an ID walked on a treadmill starting at 2.0 mph and increasing every 2 minutes by 0.5 mph until they reached 4.0 mph. Youth were affixed with a heart rate (HR) monitor. Steps were counted by trained observers using hand-tally counters. Data were collected during the final minute of each speed. HR at each speed was transformed into percentage of heart rate reserve (%HRR), using each participant's resting HR. Percentage of HRR corresponding to 40%HRR or higher was used to define MVPA. Random effects models were constructed to predict steps per minute from %HRR and participant characteristics. RESULTS: The results indicated that, on average, 122 steps·min(-1) was the minimal threshold for MVPA. Height- and age-specific steps·min(-1) ranged from 135 steps·min(-1) to 112 steps·min(-1). CONCLUSIONS: These findings provide preliminary thresholds for steps per minute that frontline practitioners working with YwID can use to promote and evaluate MVPA in this population.

The effect of physical fitness training on reaction time in youth with intellectual disabilities.

The purpose of this study was to assess whether reaction time in persons with intellectual disabilities can be improved with an exercise program. 50 children and adolescents (M age = 14.7 yr., SD = 1.4, range = 11-18) with mild intellectual disability without Downs syndrome were randomly divided into control (20 boys, 5 girls) and experimental (19 boys, 6 girls) groups. The experimental group participated in a structured physical fitness program for 12 weeks. Reaction time was assessed at baseline and after 12 weeks. Significant improvements in reaction time were observed in the exercise group but not for the control group. Results indicated that reaction time can be improved with an exercise program in youth with intellectual disability.

Autonomic response to upright tilt in people with and without Down syndrome.

This study examined whether the autonomic response to passive upright tilt as evidenced by changes in measures of heart rate and blood pressure variability differs between individuals with DS and without DS. Beat-to-beat blood pressure was measured in 26 individuals with Down syndrome (DS) and 11 individuals without DS during 5 min of rest and 5 min of upright tilt. Dependent variables included heart rate, blood pressure, frequency component measures of heart rate and blood pressure variability, and baroreflex sensitivity. The normalized high frequency (HF) power, normalized low frequency (LF) power, and LF/HF of heart rate variability, as well as the LF of blood pressure variability were reduced in persons with DS in response to upright tilt (p<0.05). This was accompanied by smaller change in baroreflex sensitivity (p<0.05) in individuals with DS. Blood pressure responses to upright tilt were also reduced in individuals with DS (p<0.05), but the heart rate response did not differ between groups. Individuals with DS show less vagal withdrawal and sympatho-excitation in response to passive upright tilt. These effects may be partially mediated by smaller change in baroreflex sensitivity in individuals with DS. The results support the hypothesis of altered autonomic modulation in people with DS.

Physical fitness predicts functional tasks in individuals with Down syndrome.

UNLABELLED: Individuals with Down syndrome (DS) exhibit reduced strength and aerobic capacity, which may limit their ability to perform functional tasks of daily living. PURPOSE: This study was conducted to examine the relationship between timed performance on functional tasks of daily living and age, knee isometric strength, and peak aerobic capacity in a group of individuals with DS. METHODS: This was a cross-sectional study involving 35 individuals (27 +/- 7.5 yr) with DS. Participants completed an isometric test of knee extensor and flexor strength, an individualized exercise test to measure peak aerobic capacity, and three timed functional tasks of daily living, which included chair rise, gait speed, and stair ascent and descent. Multiple regression analyses were performed to examine the relationship between timed task performance and age, knee isometric strength, and peak aerobic capacity. RESULTS: The multiple regression models explained 11-29% of the variance in timed task performance. Knee extensor strength was the most influential variable in predicting timed task performance (squared semipartial correlation coefficient [sr2] = 0.11-0.20), followed by aerobic capacity (sr2 = 0.10-0.14). Age was not a significant predictor of timed task performance. CONCLUSION: These findings suggest that physical fitness (defined here as aerobic capacity and knee extensor strength) limits the ability of adults with DS to perform functional tasks of daily living. Randomized controlled trials should be performed to test the probable causal relationship between exercises designed to improve physical fitness and functional tasks of daily living.

Accuracy of pedometer steps and time for youth with intellectual disabilities during dynamic movements.

Pedometer accuracy for steps and activity time during dynamic movement for youth with intellectual disabilities (ID) were examined. Twenty-four youth with ID (13 girls, 13.1 +/- 3.2 yrs; 11 boys, 14.7 +/- 2.7 yrs) were videotaped during adapted physical education class while wearing a Walk4Life 2505 pedometer in five locations around the waist. Researchers viewed each videotape and recorded observed steps and activity time. Observed findings were compared with pedometer recorded steps and time. On average, pedometer registered steps were underestimated by approximately 14% +/- 16.5%, whereas pedometer registered time was overestimated by approximately 8.7% +/- 21.8%. The findings indicate that the accuracy of pedometers may be compromised during dynamic movement for youth with ID.

Physical activity levels of children with intellectual disabilities during school.

INTRODUCTION: Current guidelines recommend school-age children accumulate at least 60 min of moderate-to-vigorous physical activity (MVPA) on most days of the week. Little is known about the activity level of school-age children with intellectual disabilities (ID). PURPOSE: To evaluate physical activity patterns of children with ID during three school settings: adapted physical education (APE, 55 min), classroom (CR, 55 min), and recess (RE, 25 min). METHODS: HR was measured by telemetry for 15 youth (6 boys, 9 girls, 8.8 +/- 2.2 yr) with ID during APE, CR, and RE on three nonconsecutive school days. Resting HR (RHR) was measured on three nonconsecutive days between 8:00 and 8:45 a.m. The mean of the five lowest RHR was used to create MVPA cutoffs. Total MVPA was determined by the mean time spent (min) above 1.25% RHR (PAHR-25 Index) in each of the three school settings. Three (one for each environment) random effects two-level models (measures nested within child) were used to describe the proportion of time students spend in MVPA across the three environments and to examine the within-child variation across measures within locations. RESULTS: The total daily MVPA across the three environments was 83.5 min (72.9-94 min). Intraclass correlations ranged from 0.06 to 0.53, suggesting considerable within-child variation across the three observations across settings. CONCLUSIONS: Although variation existed across observations for each child, on average, children met and exceeded recommendations for 60 min of MVPA during the day. Theses findings suggest that through allocation of time for APE and RE, coupled with programming designed to maximize activity opportunities, students with ID can achieve recommended levels of MVPA.

Catecholamine response to maximal exercise in persons with Down syndrome.

Individuals with Down syndrome (DS) exhibit low peak aerobic capacities and heart rates. Although autonomic modulation is attenuated in individuals with DS at rest, the exercise response appears normal. This suggests that mechanisms other than autonomic control influence the low aerobic capacity, such as catecholamine responsiveness to exercise. The purpose of this study was to determine catecholamine responses to a peak treadmill test in a group of subjects with DS compared with a nondisabled group. Epinephrine and norepinephrine concentrations were measured at rest and immediately after graded exercise tests on a treadmill in 20 subjects with DS (mean age, 24 +/- 7 years) and 21 nondisabled subjects (mean age, 26 +/- 6 years). Catecholamines increased significantly with peak exercise in the control group (p <0.05), with little to no change in subjects with DS. In conclusion, the different catecholamine responses to peak exercise, in particular the lack of a response in individuals with the DS, may be a primary mechanism to explain the reduced peak heart rates and low work capacities observed in this population.

Complexity of force output during static exercise in individuals with Down syndrome.

Force variability is greater in individuals with Down syndrome (DS) compared with persons without DS and is similar to that seen with normal aging. The purpose of this study was to examine the structure (in both time and frequency domains) of force output variability in persons with DS to determine whether deficits in force control are similar between individuals with DS and older adults. An isometric handgrip task at a constant force (30% of maximal voluntary contraction) was completed by individuals with DS (n = 29, age 26 yr), and healthy young (n = 26, age 27 yr) and older (n = 33, age 70 yr) individuals. Mean, standard deviation (SD), and coefficient of variation (CV) were used to analyze the magnitude of force output variability. Spectral analysis and approximate entropy (ApEn) were used to analyze the structure of force output variability. Mean force output for DS was lower than in young controls (P < 0.05) but no different from old controls. Individuals with DS had greater SD and CV than young and old controls (P < 0.05). The DS group had a significantly greater proportion of spectral power within the 0-to 4-Hz bandwidth than the young and older controls (P < 0.05). The DS group had significantly lower ApEn values than the young controls (P < 0.05), but there were no differences in ApEn between the DS group and the old controls (P > 0.05). In conclusion, young persons with DS demonstrate enhanced temporal structure and greater amplitude of low-frequency oscillations in the force output signal than age-matched non-DS peers. Interestingly, young persons with DS and older persons without DS have similar time-dependent structure of force output variability. This would suggest a possible link between premature aging and less complex force output in persons with DS.

Age-related changes in aerobic capacity in individuals with mental retardation: a 20-yr review.

INTRODUCTION: Persons with mental retardation (MR), particularly individuals with Down syndrome (DS), have been found to have attenuated peak exercise responses in previous research. However, it is unknown if the pattern of age-associated changes in HR or aerobic capacity (VO2peak) is similar to individuals without disabilities. PURPOSE: To investigate age-related changes in aerobic capacity in persons with MR, with and without DS, using a retrospective analysis. METHODS: Data were collected in university research laboratories, using 180 persons with MR without DS, 133 persons with MR with DS, and 322 persons without disabilities in four age categories: 9-15, 16-21, 22-29, and 30-45 yr. Subjects underwent treadmill testing with peak HR and VO2peak measurements. RESULTS: Relative VO2peak was lowest for persons with DS across all age groups. VO2peak did not change after 16 yr in the individuals with DS, whereas the other groups exhibited a slight decline (approximately 10 mL x kg(-1) x min(-1)) with age. Peak HR was overall different between all three groups (P < 0.001), and the youngest age group had the highest peak HR versus the other three age groups (P < 0.0001). CONCLUSIONS: Persons with MR without DS exhibit similar age-related changes in VO2peak and peak HR as individuals without disabilities. Similar age-related changes were also observed for peak HR in individuals with DS, despite overall lower levels. However, relative VO2peak did not decline with age in persons with DS, suggesting that aerobic capacity exhibits a different age-related response in individuals with DS.

Gait parameters in children with motor disabilities using an electronic walkway system: assessment of reliability.

PURPOSE: The study was designed to determine the reliability of temporal-spatial gait parameters in children with motor disabilities in two conditions: bare foot and with shoes and orthoses. SUBJECTS: : Nineteen children (mean age of 6.8 years) with Gross Motor Functional Classification System levels I-III participated. METHODS: Participants walked over the GAITRite(R) Walkway System and gait velocity (cm/sec), cadence (steps/min), stance time (% gait cycle), stride length (cm), base width (cm), and cycle time (sec) were evaluated. RESULTS: The single and three-trial average relative reliability estimates of the intraclass correlation coefficients met the minimum reliability coefficient criteria of 0.80. CONCLUSION: This was an initial attempt to evaluate the reliability of an instrumented walkway system. Further study should include more participants and address age, functional limitations, diagnoses, and use of assistive devices.

Accuracy of pedometer steps and time for youth with disabilities.

The purpose of the study was to examine the accuracy of pedometer steps and activity time (Walk4Life, WL) for youth with developmental disabilities. Eighteen youth (11 girls, 7 boys) 4-14 years completed six 80-meter self-paced walking trials while wearing a pedometer at five waist locations (front right, front left, back right, back left, middle back). Trials were video taped to determine actual steps and activity time. Time exhibited a smaller percent error in comparison to steps across locations. Apart from the front left, location had minimal influence on accuracy. The WL demonstrates acceptable accuracy for steps and activity time.

Case report on PWC of a competitive cyclist before and after heart transplant.

INTRODUCTION: It has been well documented that for heart transplant recipients (HTR), posttransplantation physical work capacity (PWC) normally does not exceed 60% of the value for healthy age-matched controls. Few, if any, studies have undertaken posttransplantation PWC measurements of well-conditioned individuals (i.e., PWC>300 W). CASE SUMMARY: A 37-yr-old professionally trained male cyclist suffered an acute myocardial infarction (AMI) immediately after a road race and received a heart transplant (HT) 4 months after the AMI. The participant resumed training 1 month after surgery and underwent a maximal exercise test 6 months after surgery. Peak PWC (33.8 mL.kg(-1).min(-1), 250 W) was 92% of the age-predicted maximum, and peak heart rate (165 bpm) was 96% of his known maximum. These results were similar to the participants in a study who had been training regularly for 36+/-24 months before testing, and PWC evaluations occurred 43+/-12 months after HT. CONCLUSION: Results suggest that 1) lifestyle before HT may positively affect posttransplantation PWC, 2) exercise capacity was not limited by chronotropic incompetence, and 3) a more aggressive approach to HT recovery could be applied to HTR with similar activity histories.

Promotion of physical fitness and prevention of secondary conditions for children with cerebral palsy: section on pediatrics research summit proceedings.

Inadequate physical fitness is a major problem affecting the function and health of children with cerebral palsy (CP). Lack of optimal physical activity may contribute to the development of secondary conditions associated with CP such as chronic pain, fatigue, and osteoporosis. The purpose of this article is to highlight the content and recommendations of a Pediatrics Research Summit developed to foster collaborative research in this area. Two components of physical fitness-muscle strength and cardiorespiratory fitness-were emphasized. Although there is evidence to support the use of physical fitness interventions, there are many gaps in our current knowledge. Additional research of higher quality and rigor is needed in order to make definitive recommendations regarding the mode, intensity, frequency, and duration of exercise. Outcome measurements have focused on the body functions and structures level of the International Classification of Functioning, Disability and Health (ICF), and much less is known about effects at the activities and participation levels. Additionally, the influence of nutritional and growth factors on physical fitness has not been studied in this population, in which poor growth and skeletal fragility have been identified as serious health issues. Current intervention protocols and outcome measurements were critically evaluated, and recommendations were made for future research.

The role of self-efficacy and referent specific social support in promoting rural adolescent girls' physical activity.

OBJECTIVE: To examine the role of social support (SS) and self-efficacy (SE) for physical activity (PA) in rural high school girls (N = 259, 15.5+1.2 yrs). METHODS: Using structural equation modeling, the relationships among PA, SS for PA from mother, father, and peers, and SE for overcoming barriers, seeking support, and resisting competing activities were tested. RESULTS: The effect of peer SS on PA was partially mediated through overcoming barriers. The effect of support seeking on PA was fully mediated through peer SS to overcoming barriers. Neither parent influenced PA. CONCLUSIONS: Peer SS and specific dimensions of SE should be considered in intervention studies.