Attenuated cardiovascular adjustment to sustained static exercise after carbohydrate loading

We examined whether a higher plasma lactic acid (LA) concentration resultin g from carbohydrate (CHO)-loading affects the cardiovascular responses to e xercise through a greater activation of LA-induced metaboreflex. Before and after CHO-loading, LA concentration, mean arterial blood pressure (MAP), h eart rate (HR), cardiac output (CO), rating perceived exertion (RPE), and i ntegrated electromyogram (iEMG) of the vastus lateralis were studied during a sustained static knee extension of single legs in 16 volunteers. The CHO -loading comprised an exhaustive bout of one-legged cycling (73 +/- 3% of m aximal oxygen uptake for 130-160 min) and consuming a low-CHO diet for 2-3 days and a high-CHO diet for the next 3 days. In the leg that performed the exercise (the experimental leg), the LA concentration after CHO-loading wa s significantly increased, but the magnitude of MAP, HR, and CO responses d uring static exercise was significantly decreased in parallel with a signif icant reduction of RPE and iEMG. In the control leg, there were no changes in the variables before and after CHO-loading. These results suggest that t he increased LA concentration resulting from CHO-loading did not affect the cardiovascular adjustment to the sustained exercise. Other mechanisms rela ted to the reduction of RPE and iEMG seem to be responsible for the attenua ted cardiovascular responses observed in the experimental leg after CHO-loa ding. (C) 2000 Elsevier Science B.V. All rights reserved.