Exercise-induced hyperemia is associated with knee extensor fatigability in adults with type 2 diabetes

The aim of this study was to compare fatigability, contractile function, and blood flow to the knee extensor muscles after dynamic exercise in patients with type 2 diabetes mellitus (T2DM) and controls. The hypotheses were that patients with T2DM would demonstrate greater fatigability than controls, and greater fatigability would be associated with a lower exercise-induced increase in blood flow and greater impairments in contractile function. Patients with T2DM (n = 15; 8 men; 62.4 +/- 9.0 yr; 30.4 +/- 7.7 kg/m(2); 7,144 +/- 3,294 steps/day) and 15 healthy control subjects (8 men, 58.4 +/- 6.9 yr; 28.4 +/- 4.6 kg/m(2); 7,893 +/- 2,323 steps/day) were matched for age, sex, body mass index, and physical activity. Fatigability was quantified as the reduction in knee extensor power during a 6-min dynamic exercise. Before and after exercise, vascular ultrasonography and electrical stimulation were used to assess skeletal muscle blood flow and contractile properties, respectively. Patients with T2DM had greater fatigability (30.0 +/- 20.1% vs. 14.6 +/- 19.0%, P < 0.001) and lower exercise-induced hyperemia (177 +/- 90% vs. 194 +/- 79%, P = 0.04) than controls but similar reductions in the electrically evoked twitch amplitude (37.6 +/- 24.8% vs. 31.6 +/- 30.1%, P = 0.98). Greater fatigability of the knee extensor muscles was associated with postexercise reductions in twitch amplitude (r = 0.64, P = 0.001) and lesser exercise-induced hyperemia (r = -0.56, P = 0.009). Patients with T2DM had greater lower-limb fatigability during dynamic exercise, which was associated with reduced contractile function and lower skeletal muscle blood flow. Thus, treatments focused on enhancing perfusion and reversing impairments in contractile function in patients with T2DM may offset lower-limb fatigability and aid in increasing exercise capacity. NEW & NOTEWORTHY Although prior studies compare patients with type 2 diabetes mellitus (T2DM) with lean controls, our study includes controls matched for age, body mass, and physical activity to more closely assess the effects of T2DM. Patients with T2DM demonstrated no impairment in macrovascular endothelial function, evidenced by similar flow-mediated dilation to controls. However, patients with T2DM had greater fatigability and reduced exercise-induced increase in blood flow (hyperemia) after a lower-limb dynamic fatiguing exercise compared with controls.