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Adverse Responses and Physical Activity: Secondary Analysis of the PREPARE Trial


Medicine & Science in Sports & Exercise: August 2014 - Volume 46 - Issue 8 - p 1617–1623
doi: 10.1249/MSS.0000000000000260
Applied Sciences

Physical activity has been hypothesized to cause adverse metabolic responses in a minority of participants. We use secondary analysis of a randomized controlled trial to investigate rates of adverse metabolic responses in a population at high risk of type 2 diabetes.

Methods We investigated data from the PREPARE trial; individuals with impaired glucose tolerance were randomized to the following: control (advice leaflet); intervention 1, a 3-h group-based structured education program aimed at promoting physical activity; or intervention 2, a 3-h structured education program with personalized pedometer use. Intervention 2, but not intervention 1, resulted in increased physical activity at 3, 6, and 12 months. An adverse response was defined as a change of ≥0.8 mmol·L−1 for fasting glucose, ≥1.3 mmol·L−1 for 2-h glucose, ≥0.42 mmol·L−1 for triglycerides, and −0.12 mmol·L−1 or less for HDL-cholesterol. Each group included 29 participants. Data were collected between 2006 and 2008 and analyzed in 2013.

Results In total, 12 (41%) participants in intervention 2 had an adverse response; rates in intervention 1 and the control group were 23 (79%) and 22 (76%), respectively. The odds of an adverse response were reduced in intervention 2 compared with control (OR, 0.22; 95% CI, 0.07–0.69). For the combined cohort, those who had increased physical activity at each time point had reduced odds of an adverse response compared with those who did not (OR, 0.30; 95% CI, 0.10–0.93).

Conclusion Although some individuals experienced an adverse metabolic response after a successful physical activity intervention, rates were higher under control conditions. This study does not support the hypothesis that increased physical activity per se increases the risk of an adverse metabolic response.

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1Diabetes Research Centre, University of Leicester, Leicester, England, UNITED KINGDOM; 2NIHR Leicester–Loughborough Diet, Lifestyle and Physical Activity, Biomedical Research Unit, Leicester and Loughborough, UNITED KINGDOM; 3Leicester Clinical Trials Unit, University of Leicester, Leicester, England, UNITED KINGDOM; and 4School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, England, UNITED KINGDOM

Address for correspondence: Thomas Yates, PhD, Leicester Diabetes Centre, Leicester General Hospital, Leicester, England, United Kingdom LE5 4PW; E-mail:

Submitted for publication August 2013.

Accepted for publication December 2013.

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© 2014 American College of Sports Medicine