Do Different Interval Durations of High-Intensity Interval Training Influence Blood Glucose and Lactate, and Cause Hepatic Damage in Rats?

Abstract

Background: High-intensity interval training (HIIT) is an exercise modality that can induce reactive oxygen species (ROS) production in skeletal muscles, the extent of which depends on the intensity, duration, and volume of exercise, potentially leading to oxidative stress. Objective: To analyze the effects of a single session of two HIIT protocols with different intensity levels on the markers of blood sugar, lactate, and hepatic damage in rats. Methods: Overall, 24 male Wistar rats were included in the study and divided into three groups (n = 8/group): control group (CG); short-interval HIIT (H1): HIIT involving 14 swimming periods lasting 20 s each, with 10-s intervals between each period, totaling a duration of 7 min; long-interval HIIT (H2): HIIT involving 14 swimming periods lasting 35 s each, with 25-s intervals between each period, totaling a duration of 14 min. Results: Regarding blood sugar levels, there were no significant differences in the H1 (113.00 ± 8.21 vs. 123.25 ± 10.78; p = 0.3303) and H2 (112.25 ± 12.55 vs. 114.25 ± 8.77; p = 0.9545) groups, respectively. Regarding lactate levels, there was a significant difference in both the groups compared with the CG (H1: 2.75 ± 0.55 vs. 10.06 ± 1.93; p = 0.0003; H2: 2.65 ± 1.07 vs. 9.99 ± 1.30; p = 0.0001). However, there was no difference in lactate levels between the H1 and H2 groups (10.06 ± 1.93 vs. 9.99 ± 1.30; p = 0.9965). Regarding hepatic damage, only H1 demonstrated a reduction in aspartate aminotransferase (AST) and alanine transaminase (ALT) levels compared with CG (30% and 29.65%, respectively; p < 0.05). Conversely, there were no significant differences in the AST levels between both the groups and CG (16.40 ± 1.91 [H2] vs. 13.98 ± 1.06 [CG]; –14.75%; p = 0.0918; 11.48 ± 1.59 [H1] vs. 13.98 ± 1.06 [H2]; p = 0.0792). Additionally, there was no significant difference in the ALT levels between the HIIT groups (8.54 ± 1.70 [H1] vs. 10.32 ± 0.78 [H2]; p = 0.1756). Conclusions: A single session of HIIT training with different intensity levels does not induce changes in blood sugar and lactate markers. Furthermore, short-duration HIIT induced alterations in the hepatic markers (AST and ALT) compared with the control group. However, when comparing the HIIT groups, no significant alterations were observed following a single HIIT session.