Blood Flow And Fatigability Of The Knee Extensor Muscles Across The Diabetes Spectrum

People with prediabetes (Pre-D) and type 2 diabetes (T2D) typically experience greater fatigability in their leg muscles compared to healthy controls. A key factor contributing to the increased fatigability in T2D is attenuated exercise-induced blood flow. However, this mechanism has not been studied in Pre-D. Additionally, the role of muscle oxygenation responses to fatigability in these populations remains poorly understood. PURPOSE: To determine the blood flow and muscle oxygenation responses during dynamic exercise and examine their association with lower limb fatigability in Pre-D and T2D. METHODS: 20 people with Pre-D (HbA1c = 5.7 ± 0.3) [9 males; 11 females (58 ± 16 yr)], 10 people with T2D (HbA1c = 7.0 ± 1.1) [8 males; 2 females (57 ± 13 yr)], and 26 healthy controls (HbA1c = 5.3 ± 0.2) [9 males; 17 females (55 ± 12 yr)] performed 80 maximal velocity contractions (1 every 3 s) of the knee extensor muscles lifting a load equivalent to 20% of maximal voluntary isometric contraction. Superficial femoral artery blood flow was measured before and immediately post-exercise using doppler ultrasonography. Tissue oxygenation (StO2) and deoxygenated hemoglobin (deoxy[heme]) responses of the rectus femoris were measured during exercise using near-infrared spectroscopy. RESULTS: Fatigability (% reduction in power) was greater in T2D than Pre-D (56 ± 15% vs. 36 ± 15%; p = 0.003) and controls (56 ± 15% vs. 31 ± 15%; p < 0.001) but did not differ between Pre-D and controls (p = 0.41). Post-exercise blood flow normalized to thigh lean mass was attenuated in T2D compared to Pre-D (75 ± 33 vs. 139 ± 38 ml/min/kg; p < 0.001) and controls (75 ± 33 vs. 163 ± 33 ml/min/kg; p < 0.001), and Pre-D had attenuated blood flow responses compared to controls (p = 0.04). Fatigability was associated with end-exercise blood flow (r = -0.45; p < 0.001). There were no differences in StO2 and deoxy[heme] responses during exercise between groups (group effect; p > 0.05). CONCLUSIONS: Exercise-induced blood flow was attenuated in both people with Pre-D and T2D compared to healthy controls and associated with fatigability. These data suggest impaired exercise blood flow contributes to fatigability across the diabetes spectrum. Interventions targeting improvements in exercise blood flow may be beneficial for improving fatigability associated with Pre-D and T2D. Supported by: National Center for Advancing Translational Sciences Grant 2TL1R001437 (B. E. Arney), National Institute of Aging Grant R01-AG-048262 (to S. K. Hunter, C. W. Sundberg, and R. H. Fitts), National Institute of Aging Grant R01-AG-077688-01 (to S. K. Hunter and C. W. Sundberg)