News & Views from the Editor-in-Chief - L. Bruce Gladden
Three unique papers from different areas are highlighted in this month's journal. First, Sticka et al. investigated Glucose Transporter 4 (GLUT4), the insulin-stimulated glucose transporter that facilitates glucose transport into cells. Exercise also stimulates GLUT4 via an insulin-independent pathway. Impaired GLUT4 translocation to the cell membrane is likely one of the first manifestations in developing type 2 diabetes (T2D). Current T2D diagnostic methods are indirect and do not allow for early detection. Furthermore, quantification of GLUT4 requires an invasive biopsy. These authors reported for the first time an exercise-induced increase in GLUT4 in white blood cells akin to what is reported in muscle, indicating that blood might serve as a proxy tissue for measuring GLUT4. Unlike other reports on GLUT4, an enzyme-linked immunosorbent assay (ELISA) was used; this is an easy technique that is very common in clinical analysis.
Previous reports on the autonomic response to overload training have been inconclusive, and past work relied solely on indirect measures of autonomic activity. In my second highlight, Coates et al. used microneurography to directly assess muscle sympathetic nerve activity (MSNA) following overload training (additional high load training sessions) in recreational endurance athletes. They found that regularly-training controls increased their cycling performance and had improvements in heart rate variability and cardiac baroreflex sensitivity, without changes in MSNA. In contrast, overload training resulted in a decrease in performance and an increase in MSNA, with no changes in heart rate measures. Accordingly, it appears that overload training in recreational athletes increases sympathetic activity, and this autonomic alteration was related to a blunting of the adaptive response to regular exercise. These results could inform future monitoring and training prescription in this athletic population.
Finally, Lee et al. investigated the effectiveness of progressive aerobic interval training in cardiac rehabilitation. Their major finding was that a structured, progressive program of aerobic interval training (AIT) consisting of walk/jog intervals performed in a standard, 6-month, outpatient cardiac rehabilitation (CR) setting was superior to usual care CR involving moderate-intensity continuous exercise. AIT elicited greater improvements in aerobic exercise capacity (VO2peak) in stable patients with coronary artery disease (CAD). Importantly, the authors also report the results of the implementing a more progressive version of AIT, where the emphasis is not placed on unwieldy heart rate or VO2 values that have recently been shown to be unfeasible in similar populations of heart failure patients, and CAD patients. These findings may have important implications for the way in which we approach exercise training in the rehabilitation setting, with the ultimate goal of improving patient health outcomes and survival.
L. Bruce Gladden
School of Kinesiology