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Medicine & Science in Sports & Exercise:
doi: 10.1249/01.MSS.0000385067.94501.d0
C-26 Free Communication/Poster - Objective Measures: Accelerometry and Pedometry: JUNE 3, 2010 7:30 AM - 12:30 PM: ROOM: Hall C

Investigation of Methods to Determine Individualized Thresholds for Moderate and Vigorous Intensity from Accelerometer Measurements: 2014: Board #143 June 3 8:00 AM - 9:30 AM

Kaminsky, Leonard A. FACSM1; Cochran, Heather L.2; Hargens, Trent A.1; Strath, Scott J.3

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Author Information

1Ball State University, Muncie, IN. 2Ball Memorial Hospital, Muncie, IN. 3University of Wisconsin - Milwaukee, Milwaukee, WI.

Email: kaminskyla@bsu.edu

(No disclosure reported)

Accelerometers are being widely used to quantify individuals' physical activity (PA) profiles. An important component of the PA assessment is the quantification of time spent in moderate-intensity or higher PA. This is typically performed with the use of absolute intensity thresholds.

PURPOSE: The primary purpose of this study was to determine the actual relative PA intensity, as a percentage of oxygen uptake reserve (VO2R), while meeting the absolute thresholds of 1953 activity counts/minute for moderate- and 5725 activity counts/minute for vigorous-intensity. This study also evaluated how much activity counts/minute variability existed between subjects at a VO2R of 40% and 60%.

METHODS: Twenty-eight individuals, 13 men (22.7±2.5 years), and 15 women (23.2±2.8 years), completed a maximal exercise test to determine their maximal heart rate (HRmax) and VO2. Six men and 4 women had VO2max considered high fit (≥ 80th%ile for age and gender) and 3 men and 5 women were considered low fit (≤ 20th%ile). On a separate day, subjects completed a submaximal exercise session, which was terminated when he/she reached 85% of HRmax. This exercise session included up to ten 5-minute stages, beginning at 1.5 mph followed by 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0, 7.0 and 8.0 mph. Subjects' VO2, HR, and activity counts/minute (measured using ActiGraph GT1M; ActiGraph, Pensacola, FL) were recorded every minute during the exercise session.

RESULTS: Subjects' actual relative intensity at the absolute moderate- and vigorous-intensity thresholds of 1953 and 5725 activity counts/minute were 15±6% and 45±12% VO2R, respectively. The activity counts/minute ranged from 3340 to 8250 and from 5250 to 12364 when subjects achieved 40% and 60% VO2R, respectively. Intraclass correlations (ICC) between activity counts/minute determined by both VO2R and age-predicted HRR were significant (p<0.05) at both at moderate-intensity (ICC= 0.77) and at vigorous-intensity (ICC= 0.85).

CONCLUSION: The absolute intensity thresholds do not accurately represent the actual relative intensity for most individuals. These results emphasize the need for establishing a relative activity counts/minute threshold when using accelerometers to accurately determine an individual's time spent in moderate-intensity or higher PA.

©2010The American College of Sports Medicine

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