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

Abstract

We tested the hypothesis that type 2 diabetes (T2D) alters the profile of muscle fractional oxygen (O2) 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, Δ[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 %Δ[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 (1.810.61 vs 1.350.43). Both groups displayed a near-plateau in Δ[HHb+Mb] at an exercise intensity (%PO) not different among them. Such findings suggest that a reduced O2 delivery to active muscles is an important underlying cause of exercise intolerance during a maximum graded test in middle-aged individuals with T2D.

The effect of the fraction of inspired oxygen on the NIRS-derived deoxygenated hemoglobin “breakpoint” during ramp-incremental test

“…It is noteworthy that despite the upshift in [HHb] profile, the amplitude and slopes of the signal (i.e., before and after [HHb] bp ) were the same among conditions (i.e., HYPO, NORM, and HYPER). Previous studies have shown that NIRS-derived slopes during an RI test might be affected by other interventions, such as body posture and metabolic diseases (19,23,56), whereas in the present study, the acute FI O 2 did not have any effect. Considering these results, it could be suggested that the physiological mechanisms underpinning the [HHb] signal responses and, in particular, the occurrence of the [HHb] plateau-like response at the end of the RI test might be similar regardless of the FI O 2 utilized and be driven by the achievement of a common metabolic milieu within the exercising musculature.…”

Time course of changes in V̇o2peak and O2 extraction during ramp cycle exercise following HIIT versus moderate-intensity continuous training in type 2 diabetes

“…Indeed an impaired peripheral O2 delivery extant during maximal exercise in this clinical population has been documented. Specifically reductions in maximum leg haemodynamic and vasodilatory responses during an incremental calf plantar-flexion exercise (26) as well as alterations in the profile of muscle fractional O2 extraction at the interface of the capillary to myocyte within the vastus lateralis muscle in individuals with uncomplicated T2D during ramp incremental cycle exercise (18) have been reported. Therein, Gildea et al (18) observed that T2D induced a greater reliance on NIRS-derived O2 extraction for a given PO compared with healthy controls despite a similar rate of increase in V ̇O2 relative to PO (i.e.…”

“…Regarding peripheral O2 delivery constraints, Kiely et al (26) initially reported reduced peak leg haemodynamic and vasodilatory responses during an incremental calf plantar-flexion exercise in uncomplicated T2D. More recently, Gildea et al (18), reported a significant reduction in V ̇O2peak accompanied by a greater reliance in fractional oxygen extraction during ramp incremental cycling exercise, in a similar cohort of individuals with T2D compared with healthy controls. This was depicted by an increased near-infrared spectroscopy (NIRS)-derived rate of muscle deoxygenation (i.e., deoxygenated haemoglobin and myoglobin, [HHb + Mb]) which is suggestive of lower microvascular blood flow responses likely due to maldistribution of active muscle blood flow in T2D (18).…”

“…The impairments in V ̇O2peak in T2D might be influenced by cardiovascular limitations at a systemic level, such as impaired left ventricular filling (68, 69), and limitations in peripheral vasodilation and/or microvascular function in the lower limbs (5,18,19,25,27,32,49,52,65). Regarding peripheral O2 delivery constraints, Kiely et al (26) initially reported reduced peak leg haemodynamic and vasodilatory responses during an incremental calf plantar-flexion exercise in uncomplicated T2D.…”

Priming exercise accelerates oxygen uptake kinetics during high-intensity cycle exercise in middle-aged individuals with type 2 diabetes

“…• O 2 τ p in T2D remain to be elucidated, but accumulating evidence suggests that impairments in oxygen supply to the active musculature (Padilla et al, 2006;MacAnaney et al, 2011;Kiely et al, 2014) and a subsequent mismatch of local O 2 delivery to muscle V • O 2 (Bauer et al, 2007;Gildea et al, 2019;Rocha et al, 2019;Gildea et al, 2021b) play an important role.…”