Post-exercise hypotension in male spontaneously hypertensive rats: The issue of calculation method

Abstract

In spontaneously hypertensive rats, exercise can lead to a post-exercise decrease in blood pressure, named post-exercise hypotension (PEH). This can be following physical training but also after a single bout of mild to moderate exercise when measured with tail-cuff or externalized catheter methods. Our aim was to assess the PEH obtained with different calculation methods and to compare the magnitude of this effect induced by a moderate-intensity continuous exercise or a high-intensity intermittent exercise. Thirteen 16-week-old male spontaneously hypertensive rats performed two types of aerobic exercise (continuous or intermittent) on a treadmill. Arterial pressure was recorded by telemetry for 24 h which was started 3 h before physical exercise. Based on the literature, PEH was first evaluated with two different baseline values, and then with three different approaches. We observed that the identification of PEH depended on the method used to measure the rest value, and that its amplitude was also influenced by the calculation approach and the type of exercise performed. Hence, the calculation method and the amplitude of the detected PEH can significantly influence their physiological and pathophysiological inferences.

Keywords: blood pressure variability; hypertension; physical exercise; telemetry.

FIGURE 1

Study design and protocols of exercise. (a) Study design: All animals performed three interventions (rest, exercise A: MICE, exercise B: HIIE) in a randomized order. (b) Schematic representation of the two types of exercise tests.

FIGURE 2

Recording of mean arterial pressure (MAP) during 24 h in a typical SHR. (a): Filled arrowheads indicate a change in acquisition frequency, 1: Pre‐exercise, 2: Exercise, 3: Post‐exercise. The vertical dashed line indicates the end of the night period. (b): MAP 3 h before the exercise period in one SHR. Black horizontal bars below the trace correspond to bursts of MAP increase. N = 13 rats.

FIGURE 3

Arterial pressure before, during, and after the two types of exercise. PR: Pre‐exercise, EX: Exercise, PO: Post‐exercise. Baseline 1 (black line) represents the resting value measured 10 min before the experiment, and baseline 2 (dashed line) represents the average resting value 3 h before the experiment. Values are means ± SE for 13 rats. Different from rest value of baseline 1: *p < 0.05, “p < 0.01, $p < 0.001.

FIGURE 4

Baseline data analysis. (a) Correlation between baseline 1 and 2, (b) Plot of differences between baseline 1 and 2 versus the mean of the two measurements. The bias of −14 mmHg is represented by the gap between the X axis, corresponding to zero differences, and the parallel dashed line to the X axis. N = 13 rats.

FIGURE 5

Delta of mean arterial pressure for each exercise according to three methods of measure. The delta was measured with baseline 1. MICE: Moderate‐intensity intermittent exercise, HIIE: High‐intensity intermittent exercise. Equation 1 (PEH I: Up): Post‐exercise ‐ pre‐exercise; equation 2 (PEH II; middle): Post‐exercise ‐ post‐control; equation 3 (PEH III; down): (post‐exercise ‐ pre‐exercise) ‐ (post‐control ‐ pre‐control). Values are means ± SE for 13 rats. Different from MICE value at the same time: *p < 0.05.