Metabolic Effects of Exercise Training Among Fitness-Nonresponsive Patients With Type 2 Diabetes: The HART-D Study

OBJECTIVE To evaluate the impact of exercise training (ET) on metabolic parameters among participants with type 2 diabetes mellitus (T2DM) who do not improve their cardiorespiratory fitness (CRF) with training. RESEARCH DESIGN AND METHODS We studied participants with T2DM participating in the Health Benefits of Aerobic and Resistance Training in Individuals With Type 2 Diabetes (HART-D) trial who were randomized to a control group or one of three supervised ET groups for 9 months. Fitness response to ET was defined as a change in measured peak absolute oxygen uptake (Delta VO2peak, in liters per minute) from baseline to follow-up. ET participants were classified based on Delta VO2peak into fitness responders (Delta VO2peak >= 5%) and nonresponders (Delta VO2peak <5%), and changes in metabolic profiles were compared across control, fitness responder, and fitness nonresponder groups. RESULTS A total of 202 participants (mean age 57.1 +/- 7.9 years, 63% women) were included. Among the exercise groups (n = 161), there was substantial heterogeneity in Delta VO2peak; 57% had some improvement in CRF (Delta VO2peak >0), with only 36.6% having a >= 5% increase in VO2peak. Both fitness responders and nonresponders (respectively) had significant improvements in hemoglobin A(1c) and measures of adiposity (Delta HbA(1c): -0.26%[95% CI -0.5 to -0.01] and -0.26%[-0.45 to -0.08]; Delta waist circumference: -2.6 cm [-3.7 to -1.5] and -1.8 cm [-2.6 to -1.0]; Delta body fat: -1.07% [-1.5 to -0.62] and -0.75% [-1.09 to -0.41]). No significant differences were observed in the degree of change of these metabolic parameters between fitness responders and nonresponders. Control group participants had no significant changes in any of these metabolic parameters. CONCLUSIONS ET is associated with significant improvements in metabolic parameters irrespective of improvement in cardiorespiratory fitness.