Exercise timing and blood lactate concentrations in individuals with type 2 diabetes

The purpose of this study was to characterize how resistance exercise prior to or after a meal alters fasting and postprandial blood lactate concentrations in individuals with type 2 diabetes. Obese individuals with type 2 diabetes (N = 12) completed three 2-day trials, including (i) no exercise (NoEx), (ii) resistance exercise prior to dinner (Ex-M), and (iii) resistance exercise beginning at 45 min postdinner (M-Ex). During day 1 of each trial, fasting and postprandial blood lactate concentrations, perceived exertion, and substrate oxidation were measured, and subsequently on day 2 the following morning fasting blood lactate was measured. The premeal lactate incremental area under the curve (iAUC) during Ex-M (109 ± 66 mmol·L^-1·1.6 h^-1) was over 100-fold greater (P < 0.01) compared with NoEx (-15 ± 24 mmol·L^-1·1.6 h^-1) and M-Ex (-2 ± 18 mmol·L^-1·1.6 h^-1). The postprandial lactate iAUC during M-Ex (304 ± 116 mmol·L^-1·4 h^-1) was over 2-fold greater (P < 0.01) compared with NoEx (149 ± 74 mmol·L^-1·4 h^-1) and Ex-M (-140 ± 196 mmol·L^-1·4 h^-1). Average lactate during exercise was ∼45% greater (P = 0.03) during M-Ex (3.2 ± 0.9 mmol/L) compared with Ex-M (2.2 ± 0.9 mmol/L), but the change in lactate during Ex-M (2.4 ± 1.6 mmol/L) or M-Ex (2.3 ± 1.3 mmol/L) was not different (P > 0.05). Perceived exertion, substrate oxidation, or fasting blood lactate concentrations the day after testing were not different between trials. Blood lactate concentrations during acute resistance exercise are greater when exercise is performed in the postprandial period. Acute resistance exercise performed the night prior does not alter fasting blood lactate concentrations the following morning.