Cardiac Output Is Not Related to the Slowed O2 Uptake Kinetics in Type 2 Diabetes

MAC ANANEY, O., J. MALONE, S. WARMINGTON, D. O'SHEA, S. GREEN, and M. EGANA. Cardiac Output Is Not Related to the Slowed O-2 Uptake Kinetics in Type 2 Diabetes. Med. Sci. Sports Exerc., Vol. 43, No. 6, pp. 935-942, 2011. Purpose: This study aimed to investigate whether cardiac output (CO) responses were related to V (over dot)O-2 kinetics during cycling in type 2 diabetes. Methods: A total of 9 middle-aged women with uncomplicated type 2 diabetes, 9 nondiabetic overweight women, and 11 nondiabetic lean women were recruited. Initially, the ventilatory threshold (VT) and peak V (over dot)O-2 were determined during a maximal graded test. Then, on two separate days, subjects completed three 7-min bouts of constant-load cycling at each of three intensities: 50% VT, 80% VT, and midpoint between VT and peak V (over dot)O-2 (50% Delta). CO (inert gas rebreathing) was recorded at 30 and 240 s of an additional bout at each intensity. V (over dot)O-2 kinetic parameters were determined by fitting a biexponential (50% VT and 80% VT) or triexponential (50% Delta) function to the V (over dot)O-2 data. Results: Peak V (over dot)O-2 was significantly lower in type 2 diabetes compared with the two nondiabetic groups (P < 0.05). The time constant of phase 2 was significantly greater (P G 0.05) in type 2 diabetes compared with the nondiabetic heavy and lean groups at 50% VT (34.2 +/- 15.7 vs 15.4 +/- 7.3 and 20.2 +/- 9.7 s) and 80% VT (39.1 +/- 9.0 vs 24.8 +/- 8.8 and 36.8 +/- 7.9 s), but none of the V (over dot)O-2 kinetic parameters were different at 50% Delta. CO responses during exercise were not different among the three groups, and at 80% VT, the change in CO from 30 to 240 s was significantly larger in type 2 diabetes compared with the two nondiabetic groups. Conclusions: The results confirm that type 2 diabetes slows the dynamic response of V (over dot)O-2 during light and moderate relative intensity exercise in females but that this occurs in the absence of any slowing of the CO response during the initial period of exercise.