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Chest. 2014 Aug;146(2):318-327. doi: 10.1378/chest.13-1968.

Standardizing the analysis of physical activity in patients with COPD following a pulmonary rehabilitation program.

Author information

1
Faculty of Kinesiology and Rehabilitation Sciences, Department of Rehabilitation Sciences, KU Leuven, Leuven, Belgium; Respiratory Rehabilitation and Respiratory Division, University Hospital Leuven, Leuven, Belgium.
2
Faculty of Kinesiology and Rehabilitation Sciences, Department of Rehabilitation Sciences, KU Leuven, Leuven, Belgium; Respiratory Rehabilitation and Respiratory Division, University Hospital Leuven, Leuven, Belgium; Department of Allied Health Professions, Fontys University of Applied Sciences, Eindhoven, The Netherlands.
3
Respiratory Rehabilitation and Respiratory Division, University Hospital Leuven, Leuven, Belgium.
4
Faculty of Kinesiology and Rehabilitation Sciences, Department of Rehabilitation Sciences, KU Leuven, Leuven, Belgium; Respiratory Rehabilitation and Respiratory Division, University Hospital Leuven, Leuven, Belgium. Electronic address: thierry.troosters@med.kuleuven.be.

Abstract

BACKGROUND:

There is a wide variability in measurement methodology of physical activity. This study investigated the effect of different analysis techniques on the statistical power of physical activity outcomes after pulmonary rehabilitation.

METHODS:

Physical activity was measured with an activity monitor armband in 57 patients with COPD (mean ± SD age, 66 ± 7 years; FEV1, 46 ± 17% predicted) before and after 3 months of pulmonary rehabilitation. The choice of the outcome (daily number of steps [STEPS], time spent in at least moderate physical activity [TMA], mean metabolic equivalents of task level [METS], and activity time [ACT]), impact of weekends, number of days of assessment, postprocessing techniques, and influence of duration of daylight time (DT) on the sample size to achieve a power of 0.8 were investigated.

RESULTS:

The STEPS and ACT (1.6-2.3 metabolic equivalents of task) were the most sensitive outcomes. Excluding weekends decreased the sample size for STEPS (83 vs 56), TMA (160 vs 148), and METS (251 vs 207). Using 4 weekdays (STEPS and TMA) or 5 weekdays (METS) rendered the lowest sample size. Excluding days with < 8 h wearing time reduced the sample size for STEPS (56 vs 51). Differences in DT were an important confounder.

CONCLUSIONS:

Changes in physical activity following pulmonary rehabilitation are best measured for 4 weekdays, including only days with at least 8 h of wearing time (during waking hours) and considering the difference in DT as a covariate in the analysis.

TRIAL REGISTRY:

ClinicalTrials.gov; No.: NCT00948623; URL: www.clinicaltrials.gov.

PMID:
24603844
PMCID:
PMC4122275
DOI:
10.1378/chest.13-1968
[Indexed for MEDLINE]
Free PMC Article
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