Haydn Jarrett

Interinstrument Reliability of the ActiGraph GT3X+ Ambulatory Activity Monitor During Free-Living Conditions in Adults

BACKGROUND Currently, no studies have investigated interinstrument reliability of the ActiGraph (AG) GT3X+ in free-living conditions. METHODS Nineteen adults (11 males, 8 females; aged 36.8 ± 11.9 years) wore a pair of AGs (one on each hip), during all waking hours for 1 day. Raw outputs were generated for total counts, steps, wear time and mean counts per minute. Intensity outputs were derived for time (minutes) spent in <moderate, moderate, vigorous, very vigorous and moderate-to-vigorous physical activity (MVPA). Intraclass correlation (ICC), absolute percent difference (APD), coefficient of variation (CV), Bland-Altman plots, and paired t tests were used to evaluate reliability. RESULTS Interinstrument reliability was high (CV < 5%) for raw count and derived intensity outputs, except vigorous and very vigorous activity. ICC, CV, and APD values for vigorous and very vigorous were .97, 12.28, 17.36% and .98, 18.15, 25.67%, respectively. Amalgamating moderate, vigorous, and very vigorous into a single MVPA category reduced the CV and APD values to 2.85 and 4.02%, and increased the ICC value to .99. No significant differences were found between contralateral units for any outputs (P > .05). CONCLUSION Reliability decreases beyond moderate intensities. MVPA displays superior interinstrument reliability than individual intensity categories. Research question permitting, reporting time in MVPA may maximize reliability.

Accelerometer Validation of Questionnaires Used in Clinical Settings to Assess Mvpa

INTRODUCTION The exercise vital sign (EVS) and General Practice Physical Activity Questionnaire (GPPAQ) are questionnaires designed for clinical settings to identify individuals who are not meeting physical activity (PA) guidelines in the United States and United Kingdom, respectively. To date, neither has been objectively validated. METHODS Subjects (N = 76) from the United States (n = 38; age, 49 ± 20 yr) and United Kingdom (n = 38; age, 43 ± 21 yr) completed a health history questionnaire, wore an accelerometer for 7 d, and then completed the EVS and GPPAQ. Accelerometry, EVS, and GPPAQ data were scored to dichotomize subjects into groups of meeting (≥150 min of moderate-to-vigorous PA (MVPA) per week) or not meeting (<150 min of MVPA per week) the PA guidelines, and accelerometry was used as a criterion measure for comparing both questionnaires. The sensitivity and specificity of the EVS and GPPAQ were calculated to represent the ability of the questionnaires to identify subjects who did not and did meet the PA guidelines. Total MVPA accumulated in ≥10-min bouts were compared between accelerometry and the EVS using a 2 × 2 × 2 repeated measures ANOVA with one within-subjects effect (PA assessment method) and two between-subjects effects (gender and country). The alpha level was P = 0.05 for all analyses. RESULTS The EVS had marginally better sensitivity (59% vs 46%) and specificity (77% vs 50%) than the GPPAQ. The EVS grossly overestimated the minutes of MVPA when compared to accelerometry (P < 0.05) for all subjects, except UK women. CONCLUSION In practice, the EVS and GPPAQ may not identify ∼50% of patients who should be advised to increase their PA. Therefore, physicians should advocate that all of their patients adopt an active lifestyle, including the achievement of ≥150 min of MVPA per week.