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Exercise Dose, Exercise Adherence, and Associated Health Outcomes in the TIGER Study

Miller, Fred L.1; O’Connor, Daniel P.2; Herring, Matthew P.3; Sailors, Mary H.4; Jackson, Andrew S.2; Dishman, Rodney K.5; Bray, Molly S.3

Medicine & Science in Sports & Exercise: January 2014 - Volume 46 - Issue 1 - p 69–75
doi: 10.1249/MSS.0b013e3182a038b9
Epidemiology

Purpose: To effectively evaluate activity-based interventions for weight management and disease risk reduction, objective and accurate measures of exercise dose are needed. This study examined cumulative exercise exposure defined by HR-based intensity, duration, and frequency as a measure of compliance with a prescribed exercise program and a predictor of health outcomes.

Methods: One thousand one-hundred fifty adults (21.3 ± 2.7 yr) completed a 15-wk exercise protocol consisting of 30 min·d−1, 3 d·wk−1, at 65%–85% maximum HR reserve. Computerized HR monitor data were recorded at every exercise session (33,473 valid sessions). To quantify total exercise dose, duration for each session was adjusted for average exercise intensity (%HR reserve) to create a measure of intensity minutes for each workout, which were summed over all exercise sessions to formulate an HR physical activity score (HRPAS). Regression analysis was used to examine the relation between HRPAS and physiological responses to exercise training. Compliance with the exercise protocol based on achievement of the minimum prescribed HRPAS was compared with adherence defined by attendance.

Results: On the basis of HRPAS, 868 participants were empirically defined as compliant, and 282 were noncompliant. HRPAS-based and attendance-based classifications of compliance and adherence differed in approximately 9% of participants. Higher HRPAS was associated with significant positive changes in body mass (P < 0.001), body mass index (P < 0.001), waist and hip circumferences (P < 0.001), percent body fat (P < 0.001), systolic blood pressure (P < 0.011), resting HR (P < 0.003), fasting glucose (P < 0.001), and total cholesterol (P < 0.02). Attendance-based adherence was associated with body mass, hip circumference, percent body fat, resting HR, and cholesterol (P < 0.05).

Conclusions: The HRPAS is a quantifiable measure of exercise dose associated with improvement in health indicators beyond that observed when adherence is defined as session attendance.

1Department of Kinesiology, Anderson University, Anderson, IN; 2Department of Health and Human Performance, University of Houston, Houston, TX; 3Department of Epidemiology, University of Alabama at Birmingham, Birmingham, AL; 4Symptom Research CAO, The University of Texas MD Anderson Cancer Center, Houston, TX; and 5Department of Kinesiology, The University of Georgia, Athens, GA

Address for correspondence: Molly S. Bray, Ph.D., Genomics Core Laboratory, Heflin Center for Genomic Sciences, University of Alabama at Birmingham, 1720 2nd Avenue South, RPHB 230H, Birmingham, AL 35294; E-mail: mbray@uab.edu.

Submitted for publication January 2013.

Accepted for publication June 2013.

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© 2014 American College of Sports Medicine