TY - JOUR
T1 - How many days are enough? A study of 365 days of pedometer monitoring
AU - Kang, Minsoo
AU - Bassett, David R.
AU - Barreira, Tiago V.
AU - Catrine, Tudor Locke
AU - Ainsworth, Barbara
AU - Reis, Jared P.
AU - Strath, Scott
AU - Swartz, Ann
PY - 2009/9
Y1 - 2009/9
N2 - This study was designed to determine the number of days of pedometer monitoring necessary to achieve reliable and valid estimates of a 1-year average of step counts in adults based on either consecutive days (CD) or random days (RD) of data collection. Twenty-three participants (16 women; M age = 38 years, SD = 9.9) wore a Yamax SW 200 pedometer and recorded their step counts for 365 consecutive days. Nine measurement periods of various lengths were selected (2, 3, 4, 5, 6, 7, 14, 21, and 30 days). Each measurement period was randomly selected 10 times each for CD and RD from the larger database. For reliability and validity, two-way intraclass correlation coefficients and mean absolute percentage error (MAPE) were calculated, respectively. The year-round average was considered the criterion measure of the “true” habitual physical activity. Data were analyzed separately by CD and RD. At least 5 CD or 6 RD were necessary to achieve an ICC of 80. A minimum of 30 CD or 14 RD were necessary to achieve an MAPE lower than 10%. These findings provide researchers and practitioners with useful information to determine appropriate measurement length and the method of data selection based on a desired level of reliability and validity.
AB - This study was designed to determine the number of days of pedometer monitoring necessary to achieve reliable and valid estimates of a 1-year average of step counts in adults based on either consecutive days (CD) or random days (RD) of data collection. Twenty-three participants (16 women; M age = 38 years, SD = 9.9) wore a Yamax SW 200 pedometer and recorded their step counts for 365 consecutive days. Nine measurement periods of various lengths were selected (2, 3, 4, 5, 6, 7, 14, 21, and 30 days). Each measurement period was randomly selected 10 times each for CD and RD from the larger database. For reliability and validity, two-way intraclass correlation coefficients and mean absolute percentage error (MAPE) were calculated, respectively. The year-round average was considered the criterion measure of the “true” habitual physical activity. Data were analyzed separately by CD and RD. At least 5 CD or 6 RD were necessary to achieve an ICC of 80. A minimum of 30 CD or 14 RD were necessary to achieve an MAPE lower than 10%. These findings provide researchers and practitioners with useful information to determine appropriate measurement length and the method of data selection based on a desired level of reliability and validity.
KW - Measurement
KW - Reliability
KW - Step counts
KW - Validity
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U2 - 10.1080/02701367.2009.10599582
DO - 10.1080/02701367.2009.10599582
M3 - Article
C2 - 19791630
AN - SCOPUS:70350136607
VL - 80
SP - 445
EP - 453
JO - Research Quarterly for Exercise and Sport
JF - Research Quarterly for Exercise and Sport
SN - 0270-1367
IS - 3
ER -