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Fig. 2 | Cardiovascular Diabetology

Fig. 2

From: Type 2 diabetes and reduced exercise tolerance: a review of the literature through an integrated physiology approach

Fig. 2

Vasogenic and neurogenic determinants of reduced exercise tolerance in type 2 diabetes. Schematic representation of two pathophysiological hypotheses explaining the alterations observed in type 2 diabetes mellitus through cardiopulmonary exercise testing. Central and peripheral (efferent fibers to lungs, heart, conduit vessels, muscle arterioles are represented on the right, while afferent fibers of muscle metaboreflex and cardiac sympathetic reflex are represented on the left of the picture) nervous system, the baroreceptor, lungs, heart, conduit vessels, muscular vasculature, oxygen diffusion from capillaries to muscle, skeletal muscle and muscle cells are schematically represented. In each hypothesis, the organ/system that is primarily impaired is colored in grey and is marked with a black cross, whilst the ones that are hyperactivated are marked with a red bolt and a red shadowing. Unaffected systems maintain their colors. Secondary involvement of other organs/systems is indicated with vertical grey arrows indicating stimulation (arrow facing up) or inhibition (arrow facing down) through known physiological mechanisms, which are represented as grey dotted lines with captions. On top of the figure, the grey text panel explains the primary involvement of the organ/system identified with the black cross and grey shadowing or the red bolt and red shadowing; the text panel beneath the figure shows a list of the altered cardiopulmonary exercise test variables observed in type 2 diabetes mellitus that may be explained by the pathophysiological hypothesis here shown. a Vasogenic determinants: impaired modulation of peripheral vascular resistances reduces muscle blood flow and oxygen diffusion, thus negatively affecting skeletal muscle performance, peripheral oxygen extraction and cardiac output through enhanced baroreflex and muscle metaboreflex activation. b Neurogenic determinants: altered autonomic tone and hyperactive muscle metaboreflex and cardiac sympathetic efferent reflex might account for impaired cardiac output, suboptimal vascular and pulmonary adjustments during exercise, eventually leading to reduced muscle perfusion and oxygen extraction (see main text for full description)

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