Fig. 1

A Schematic representation of the experimental design and HIIT protocol in hypertensive rats (SHR). At 360 days of age, all animals underwent initial evaluations, including a maximal exercise capacity test on a treadmill and systolic blood pressure measurement. A 5-day adaptation period followed, during which the animals were familiarized with the treadmill and training protocol. At 365 days of age, animals were divided into two groups: CT (hypertensive Control) and T group (hypertensive trained), with the latter undergoing a high-intensity interval training (HIIT) protocol. At 395 days of age (start of the 4th training week), a second maximal exercise capacity test was conducted to adjust training intensity. At 425 days of age (end of the 8-week protocol), the final evaluations, including exercise performance tests, were performed. Animals were euthanized at 427 days of age, and tissue samples were collected for biochemical analysis, Raman spectroscopy, histology, and immunohistochemistry. B Graphical representation of the 8-week HIIT training protocol. During the 1st and 2nd weeks, the training consisted of 5 sets of 4 min at 95% of maximum speed, alternating with 3 min at 65% of maximum speed. From the 3rd to the 6th week, the intensity remained at 95%, but the number of sets increased to 7, maintaining the same alternation of 4 min at high intensity followed by 3 min at 65%. In the 7th week, the intensity was raised to 110%, with 7 sets of 4 min at this intensity, alternating with 3 min at 65%. In the 8th and final week, the intensity increased to 115%, maintaining the structure of 7 sets of 4 min at high intensity, alternating with 3 min at 65%