IMPACT OF PHYSICAL-ACTIVITY ON CARDIOVASCULAR RISK-FACTORS IN IDDM

OBJECTIVE - To study the impact of physical activity on glycemic contr ol and plasma lipids [HDL cholesterol (HDL-C), HDL-C subfractions, tri glgcerides, lipoprotein(a)], blood pressure, weight, and abdominal fat and to determine the necessary short-term adaptations in diabetes man agement during intensive endurance training in patients with IDDM. RES EARCH DESIGN AND METHODS - Well-controlled subjects with IDDM (n = 20; HbA(1c) = 7.6%) engaged in a regular exercise program over a period o f 3 months involving endurance sports such as biking, long-distance ru nning, or hiking. Subjects were instructed to exercise at least 135 mi n per week. If baseline activity exceeded this level, subjects were to increase further their physical activity as much as possible and reco rd the type and time of such activity. RESULTS - During the 3-month in tervention, physical activity increased from 195 +/- 176 to 356 +/- 16 4 min (mean +/- SD) per week (P < 0.001). Physical fitness as assessed by Vo(2max) increased from 2,914 +/- 924 to 3,092 +/- 905 ml/min (P < 0.001), and insulin sensitivity increased significantly (steady-state plasma glucose [SSPG] decreased from 10.5 +/- 4.8 to 7.0 +/- 3.3 mmol /l; P < 0.01). Subsequently, LDL cholesterol decreased by 14% (P < 0.0 5), and HDL and HDL3-C subfraction increased by 10 (P < 0.05) and 16% (P < 0.05), respectively. Systolic and diastolic blood pressure decrea sed significantly from 127 +/- 9 to 124 +/- 8 (P < 0.05) and from 80 /- 5 to 77 +/- 5 mmHg (P < 0.001), respectively. Resting heart rate de creased from 63 +/- 6 to 59 +/- 7 bpm (P < 0.01). Waist-to-hip circumf erence ratio decreased from 0.882 +/- 0.055 to 0.858 +/- 0.053 (P < 0. 001), body weight decreased from 70.7 +/- 10.4 to 68.7 +/- 10.2 kg (P = 0.003), with a consequent decrease in body fat from 21.9 +/- 8.2 to 18.0 +/- 6.3% (P < 0.001) and an increase in lean body mass from 54.9 +/- 12.2 to 56.8 +/- 11.0 kg. These effects occurred independently of glycemic control. The overall frequency of severe hypoglycemic episode s was reduced from 0.14 to 0.10 per patient-year during the study peri od. CONCLUSIONS - This study shows that increasing physical activity i s safe and does not result in more hypoglycemic episodes and that ther e is a linear dose-response between increased physical activity and lo ss of abdominal fat and a decrease in blood pressure and lipid-related cardiovascular risk factors, with a preferential increase in the HDL3 -C subfraction.