Older Type 2 diabetic males do not exhibit abnormal pulmonary oxygen uptake and muscle oxygen utilization dynamics during submaximal cycling exercise

There are reports of abnormal pulmonary oxygen uptake ((V) over dotO(2)) and deoxygenated hemoglobin ([HHb]) kinetics in individuals with Type 2 diabetes (T2D) below 50 yr of age with disease durations of < 5 yr. We examined the (V) over dotO(2) and muscle [HHb] kinetics in 12 older T2D patients with extended disease durations (age: 65 +/- 5 years; disease duration 9.3 +/- 3.8 years) and 12 healthy age-matched control participants (CON; age: 62 +/- 6 years). Maximal oxygen uptake ((V) over dotO(2max)) was determined via a ramp incremental cycle test and (V) over dotO(2) and [HHb] kinetics were determined during subsequent submaximal step exercise. The (V) over dotO(2max) was significantly reduced (P < 0.05) in individuals with T2D compared with CON (1.98 +/- 0.43 vs. 2.72 +/- 0.40 l/min, respectively) but, surprisingly, (V) over dotO(2) kinetics was not different in T2D compared with CON (phase II time constant: 43 +/- 17 vs. 41 +/- 12 s, respectively). The Delta[HHb]/Delta(V) over dotO(2) was significantly higher in T2D compared with CON (235 +/- 99 vs. 135 +/- 33 AU . l(-1) . min(-1); P < 0.05). Despite a lower (V) over dotO(2max), (V) over dotO(2) kinetics is not different in older T2D compared with healthy age-matched control participants. The elevated Delta[HHb]/(V) over dotO(2) in T2D individuals possibly indicates a compromised muscle blood flow that mandates a greater O-2 extraction during exercise. Longer disease duration may result in adaptations in the O-2 extraction capabilities of individuals with T2D, thereby mitigating the expected age-related slowing of (V) over dotO(2) kinetics.