Chest
Volume 117, Issue 5, May 2000, Pages 1359-1367
Journal home page for Chest

Clinical Investigations
COPD
Quantitating Physical Activity in COPD Using a Triaxial Accelerometer

https://doi.org/10.1378/chest.117.5.1359Get rights and content

Study objective

To determine the reliability, validity, and stability of a triaxial accelerometer for walking and daily activity measurement in a COPD sample.

Design

Cross-sectional, correlational, descriptive design.

Setting

Outpatient pulmonary rehabilitation program in a university-affiliated Veterans Affairs medical center.

Participants

Forty-seven outpatients (44 men and 3 women) with stable COPD (FEV1, 37% predicted; SD, 16%) prior to entry into a pulmonary rehabilitation program.

Measurements and results

Test-retest reliability of a triaxial movement sensor (Tritrac R3D Research Ergometer; Professional Products; Madison, WI) was evaluated in 35 of the 47 subjects during three standardized 6-min walks (intraclass correlation coefficient [rICC] = 0.84). Pearson correlations evaluated accelerometer concurrent validity as a measure of walking (in vector magnitude units), compared to walking distance in all 47 subjects during three sequential 6-min walks (0.84, 0.85, and 0.95, respectively; p < 0.001). The validity of the accelerometer as a measure of daily activity over 3 full days at home was evaluated in all subjects using Pearson correlations with other indicators of functional capacity. The accelerometer correlated with exercise capacity (maximal 6-min walk, r = 0.74; p < 0.001); level of obstructive disease (FEV1 percent predicted, r = 0.62; p < 0.001); dyspnea (Functional Status and Dyspnea Questionnaire, dyspnea over the past 30 days, r = − 0.29; p < 0.05); and activity self-efficacy (Activity Self-Efficacy Questionnaire, r = 0.43; p < 0.01); but not with self-report of daily activity (Modified Activity Recall Questionnaire, r = 0.14; not significant). Stability of the accelerometer to measure 3 full days of activity at home was determined by an rICC of 0.69.

Conclusions

This study provides preliminary data suggesting that a triaxial movement sensor is a reliable, valid, and stable measure of walking and daily physical activity in COPD patients. It has the potential to provide more precise measurement of everyday physical functioning in this population than self-report measures currently in use, and measures an important dimension of functional status not previously well-described.

Section snippets

Materials and Methods

Two separate measurement conditions were used to estimate validity, reliability, and stability of the accelerometer in a sample of outpatients with stable, moderate to severe COPD. The first examined reliability and validity of the instrument to measure walking behavior during repeated 6MDWs; the second investigated validity of the accelerometer to measure daily activity over a 3-day period of continuous free-living at home, and stability of the measurement during this period.

Results

Twelve accelerometers were used, and each subject was assigned the same device for every measurement event. One unit malfunctioned due to failure of one of the three internal accelerometers during a measurement period at home, and the subject was retested with another device.

Discussion

This study evaluated reliability, validity, and stability of a triaxial accelerometer for measuring human movement in very sedentary COPD outpatients under two measurement conditions: the 6-min walk and during daily activity at home. The participants, most of whom had severe to very-severe obstructive disease,27 were similar to others studied at entry to pulmonary rehabilitation in terms of age, level of obstructive disease, symptom experience, and exercise capacity.13, 16 We determined that

References (29)

  • CE Mathews et al.

    Field trial of a three-dimensional activity monitor: comparison with self-report

    Med Sci Sports Exerc

    (1995)
  • CV Bouten et al.

    Daily physical activity assessment: comparison between movement registration and doubly labeled water

    J Appl Physiol

    (1996)
  • AV Ng et al.

    Quantitation of lower physical activity in persons with multiple sclerosis

    Med Sci Sports Exerc

    (1997)
  • LH Epstein et al.

    Determinants of physical activity in obese children assessed by accelerometer and self-report

    Med Sci Sports Exerc

    (1996)
  • Cited by (228)

    • Activity monitors in pulmonary disease

      2019, Respiratory Medicine
    View all citing articles on Scopus

    The research reported here was supported by the Department of Veterans Affairs, Veterans Health Administration, Health Services Research and Development Service (NRI 95-082.1). Dr. Steele is the Respiratory Clinical Nurse Specialist at VA Paget Sound Health Care Systems, Seattle, WA.

    View full text