Influence of type 2 diabetes on muscle deoxygenation during ramp incremental cycle exercise

We tested the hypothesis that type 2 diabetes (T2D) alters the profile of muscle fractional oxygen (O-2) extraction (near-infrared spectroscopy) during incremental cycle exercise. Seventeen middle-aged individuals with uncomplicated T2D and 17 controls performed an upright ramp test to exhaustion. The rate of muscle deoxygenation (i.e. deoxygenated haemoglobin and myoglobin concentration, Delta[HHb+Mb]) profiles of the vastus lateralis muscle were normalised to 100% of the response, plotted against % power output (PO) and fitted with a double linear regression model. Peak oxygen uptake was significantly (P < 0.05) reduced in individuals with T2D. The %Delta[HHb+Mb]/%PO slope of the first linear segment of the double linear regression function was significantly (P < 0.05) steeper in T2D than controls (1.59 (1.14) vs 1.23 (0.51)). Both groups displayed a near-plateau in Delta[HHb+Mb] at an exercise intensity (%PO) not different amongst them. Such findings suggest that a reduced O-2 delivery to active muscles is an important underlying cause of exercise intolerance during a maximum graded test in middle-aged individuals with T2D.