Validity of an Accelerometer-Based Activity Monitor System for Measuring Physical Activity in Frail Older Adults.

This study aimed to investigate the validity of the accelerometer-based DynaPort system to detect physical activity in frail, older subjects. Eighteen home-dwelling subjects (Groningen Frailty Indicator [GFI] score ≥ 4, ≥ 75 years) were included. Activities in their home environment were simultaneously observed by two researchers and measured with the DynaPort system during six consecutive hours. Primary outcome measures were the sensitivity and specificity of the DynaPort for locomotion (90% considered as sufficient agreement). Other outcome measures were overall agreement, and sensitivity and specificity for other activities. Sensitivity and specificity for locomotion were 83.3% and 100.0%, respectively. Overall agreement was 74.6%. Sensitivity was sufficient for sitting (94.4%), but not for lying and standing (59.2% and 69.6%, respectively). Specificity was sufficient for lying and standing (100.0% and 93.3%, respectively), but not for sitting (80.7%). In conclusion, the DynaPort system is not a valid method for assessing physical activity in frail, older subjects.

Older adults can improve compensatory stepping with repeated postural perturbations.

The ability to respond quickly and accurately to an external perturbation with a stepping response is critical to avoid falls and this ability is impaired in older, compared to young adults. However, little is known about whether young and older adults improve compensatory stepping responses similarly with practice. This study compares the extent to which young and older adults can improve, retain, and generalize postural compensatory steps in response to external perturbations. Centre of mass displacement, step characteristics and lower leg muscle activation latencies were measured during one training session of compensatory stepping in response to large surface translations in 13 young and 12 older adults. Retention was tested 24 h later. Older adults decreased their center of mass displacements over repeated exposure to large surface translations in both the anterior and posterior directions and retained these improvements. In contrast, young adults only showed adaptation and retention of forward stepping responses. Neither group was able to generalize improvements in stepping responses across directions. These results suggest step training may be beneficial for older adults, however additional, multidirectional training may be necessary to facilitate generalization of postural stepping responses for any direction of a slip or trip.

Daily physical activity in ankylosing spondylitis: validity and reliability of the IPAQ and SQUASH and the relation with clinical assessments.

INTRODUCTION: The aim of this study was to investigate the construct validity and test-retest reliability of the International Physical Activity Questionnaire (IPAQ; long form) and the Short QUestionnaire to Assess Health-enhancing physical activity (SQUASH) and to investigate the relation between daily physical activity and clinical assessments in patients with ankylosing spondylitis (AS). METHODS: For validity, the self-report questionnaires IPAQ and SQUASH were compared with daily physical activity assessed with the ActiGraph accelerometer during 7 consecutive days in 63 AS outpatients. For reliability, the IPAQ and SQUASH were administered twice approximately 1 week apart in 52 AS outpatients. In all 115 patients, clinical assessments were performed at the outpatient clinic. RESULTS: IPAQ and SQUASH total scores correlated significantly with accelerometer outcome: ρ = 0.38 and r = 0.35, respectively. Intraclass correlation coefficients between first and second assessments of the IPAQ and SQUASH were 0.83 and 0.89, respectively. Bland-Altman analyses showed no systemic bias, but in particular for the IPAQ the 95% limits of agreement were wide. Daily physical activity assessed by accelerometer, IPAQ, and SQUASH correlated significantly with disease activity, physical activity, and quality of life. A relation with spinal mobility was found only for the accelerometer and SQUASH. The direction of these correlations indicates that higher daily physical activity is related to lower disease activity and better physical function, spinal mobility and quality of life. CONCLUSIONS: Both physical activity questionnaires showed modest construct validity. The SQUASH showed good test-retest reliability, superior to the IPAQ. These results indicate that the SQUASH is more suitable than the IPAQ to assess daily physical activity in AS population studies. However, it is desirable to add questions on AS-specific physical activity. Further studies are needed to investigate the causality of the relation between daily physical activity and clinical assessments.

Variability of Stepping during a Virtual Reality Paradigm in Parkinson's Disease Patients with and without Freezing of Gait.

BACKGROUND: Freezing of gait is a common and debilitating symptom affecting many patients with advanced Parkinson's disease. Although the pathophysiology of freezing of gait is not fully understood, a number of observations regarding the pattern of gait in patients with this symptom have been made. Increased 'Stride Time Variability' has been one of the most robust of these features. In this study we sought to identify whether patients with freezing of gait demonstrated similar fluctuations in their stepping rhythm whilst performing a seated virtual reality gait task that has recently been used to demonstrate the neural correlate of the freezing phenomenon. METHODS: Seventeen patients with freezing and eleven non-freezers performed the virtual reality task twice, once whilst 'On' their regular Parkinsonian medication and once in their practically defined 'Off' state. RESULTS: All patients displayed greater step time variability during their 'Off' state assessment compared to when medicated. Additionally, in the 'Off' state, patients with freezing of gait had greater step time variability compared to non-freezers. The five steps leading up to a freezing episode in the virtual reality environment showed a significant increase in step time variability although the final three steps preceding the freeze were not characterized by a progressive shortening of latency. CONCLUSIONS: The results of this study suggest that characteristic features of gait disturbance observed in patients with freezing of gait can also be demonstrated with a virtual reality paradigm. These findings suggest that virtual reality may offer the potential to further explore the freezing phenomenon in Parkinson's disease.

Psychometric properties of the PAT: an assessment tool for ADL performance of older people living in residential homes.

BACKGROUND: As the world population ages, the number of people with diminished performance on the Activities of Daily Living (ADL) increases. A reliable and valid measure needs to be developed to determine the effects of interventions focused at increasing self-care abilities. We developed the Performance ADL Test (PAT) for this purpose. OBJECTIVE: The aim of this study was to investigate the reliability and validity of the PAT in older people living in residential homes. METHODS: The PAT contains 16 test items, covering the entire range of Basic ADL and Instrumental ADL performance in elderly people. For this assessment, 40 older people (mean age of 85 ± 7.5 years) participated. All 40 subjects lived in residential institutions in the Netherlands, were able to walk at least 10 m, could understand instructions spoken in Dutch, and had no cognitive impairment. During the first test session, subjects completed the PAT, the Groningen Activity Restriction Scale (GARS), and performance-based physical fitness tests. Two weeks later, subjects were retested on the PAT. RESULTS: Factor analysis revealed three subscales: Organization of Performance, Gross Motor Function, and Fine Motor Function. Internal consistency (Cronbach's α) of all scales and subscales ranged from 0.731 to 0.881. Test-retest reliability (intraclass correlation) ranged from 0.316 to 0.950. Paired sample t-tests revealed no significant differences between subject performance obtained during the two test periods. Pearson's correlations between the PAT and the GARS ranged from 0.490 to 0.831, and between the PAT and the fitness tests from 0.317 to 0.781. CONCLUSION: Although the number of participants was limited (n = 40), the PAT seems to be a useful instrument for assessing ADL performance in older people living in residential homes. In general, internal consistency, test-retest reliability, and validity were satisfactory.

Rehearsal strategies during motor-sequence learning in old age: execution vs motor imagery.

Motor imagery and action-based rehearsal were compared during motor sequence-learning by young adults (M = 25 yr., SD = 3) and aged adults (M = 63 yr., SD = 7). General accuracy of aged adults was lower than that of young adults (F(1,28) = 7.37, p =.01) even though working-memory capacity was equivalent in the two groups. Motor imagery and rehearsal by action increased accuracy in both age groups, compared with minimization of opportunity for rehearsal (F(1,28) = 30.95, p < .001), but no interaction was found with age group, which suggests that young and aged adults were equally capable of motor imagery and action-based rehearsal. It was assumed that differences in performance between young and aged participants related to the formation of mental representations of sequences and integration of new elements into these representations rather than the capacity for motor imagery or rehearsal by action per se. The current study was exploratory and involved a relatively small sample of 15 participants per age group. Caution must be taken when considering the results.

Detection of walking periods and number of steps in older adults and patients with Parkinson's disease: accuracy of a pedometer and an accelerometry-based method.

The aim of this study was to examine if walking periods and number of steps can accurately be detected by a single small body-fixed device in older adults and patients with Parkinson's disease (PD). Results of an accelerometry-based method (DynaPort MicroMod) and a pedometer (Yamax Digi-Walker SW-200) worn on each hip were evaluated against video observation. Twenty older adults and 32 PD patients walked straight-line trajectories at different speeds, of different lengths and while doing secondary tasks in an indoor hallway. Accuracy of the instruments was expressed as absolute percentage error (older adults versus PD patients). Based on the video observation, a total of 236.8 min of gait duration and 24,713 steps were assessed. The DynaPort method predominantly overestimated gait duration (10.7 versus 11.1%) and underestimated the number of steps (7.4 versus 6.9%). Accuracy decreased significantly as walking distance decreased. Number of steps were also mainly underestimated by the pedometers, the left Yamax (6.8 versus 11.1%) being more accurate than the right Yamax (11.1 versus 16.3%). Step counting of both pedometers was significantly less accurate for short trajectories (3 or 5 m) and as walking pace decreased. It is concluded that the Yamax pedometer can be reliably used for this study population when walking at sufficiently high gait speeds (>1.0 m/s). The accelerometry-based method is less speed-dependent and proved to be more appropriate in the PD patients for walking trajectories of 5 m or more.

Gait in ageing and associated dementias; its relationship with cognition.

The focus of this review is on the close relationship between gait and cognition in ageing and associated dementias. This close relationship is supported by epidemiological studies, clinical studies of older people with and without dementia that focused on the intensity of the physical activity, clinical studies with older persons without dementia examining a relationship between gait and specific cognitive processes, and human and animal experimental studies examining a neural basis for such a relationship. Despite these findings, most studies with patients with dementia focus exclusively on the relationship between cognition and dementia, with relatively few addressing the relationship between gait and dementia. However, subtle disturbances in gait can be observed in ageing and in (preclinical) subtypes of dementia that are not known for prominent motor disturbances, i.e. Mild Cognitive Impairment, Alzheimer's Disease, vascular Cognitive Impairment No Dementia, Subcortical Ischaemic Vascular Dementia, Frontotemporal Mild Cognitive Impairment, and Frontotemporal Dementia, supporting a close relationship between gait and cognition. The relationship between gait and cognition is weakened by the few available intervention studies that examine the effects of walking on cognition in patients with (preclinical) dementia. These studies report equivocal results, which will be discussed. Finally, suggestions for future research will be made.