Blood Flow and Fatigability of the Knee Extensor Muscles in Individuals with Prediabetes
Authors: Arney Blaine , Fulton Timothy , Vosters Emma , Kern Leah , Wrucke David , Sundberg Christopher , Hunter Sandra 
Published: May 2023

The mechanisms of increased lower limb fatigability during dynamic contractions in individuals with prediabetes are unresolved. Vascular dysfunction in people with prediabetes is a likely mechanism but has not been investigated. The purpose of this study was to determine the blood flow and muscle tissue oxygenation responses during exercise and their association with the increased fatigability of the lower limb in prediabetes. We hypothesized that individuals with prediabetes would have an attenuated blood flow and muscle oxygenation during exercise that would be associated with an increased fatigability. METHODS: Six individuals with prediabetes (HbA1c = 5.8 ± 0.2) [3 men; 3 women (74.1 ± 2.9 yr)] and six healthy control participants [3 men; 3 women (77.5 ± 5.4 yr)], matched for sex, age, physical activity, and body mass index, 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) of the rectus femoris was measured during exercise using near-infrared spectroscopy (NIRS). RESULTS: Fatigability (% reduction in power of the knee extensors) did not differ between individuals with prediabetes and healthy controls (40.2 ± 28.0% vs. 31.0 ± 15.0%, p = 0.49, d = 0.41). Based on previous data investigating the effect of prediabetes on fatigability, a power analysis revealed an appropriate sample size to be ≈ 40 participants (20 per group). Post-exercise blood flow normalized to thigh lean mass did not differ between individuals with prediabetes and controls (173.6 ± 32.3 ml/min/kg vs. 148.5 ± 50.9 ml/min/kg, p = 0.33, d = 0.59), nor did exercise-induced blood flow (% of baseline) (622 ± 245% vs. 459 ± 216%, p = 0.25, d = 0.71). There was no association between fatigability and exercise-induced blood flow ( r = -0.17; p = 0.60). NIRS data was only obtained from four participants (eight participants excluded due to subcutaneous adipose tissue thickness > 2 cm). End of exercise StO2 (% physiological range) was 47.5 ± 12.3% for individuals with prediabetes (n = 2) and 47.2 ± 8.0% for controls (n = 2). Exercising nadir StO2 was 27.8 ± 11.1% for individuals with prediabetes (n = 2) and 28.3 ± 3.0% for controls (n = 2). CONCLUSION: These preliminary results suggest that lower limb fatigability in individuals with prediabetes and healthy controls may not be explained by blood flow and muscle oxygenation responses during exercise. This research is Supported by the National Center for Advancing Translational Sciences, National Institutes of Health 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). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.