Does hypertension exacerbate the age-related exaggerated pressor response to dynamic exercise during post-exercise muscle ischemia?

Abstract

Hypertension is known to augment exercise blood pressure (BP). Aging also potentiates BP response to ischemic dynamic exercise. However, whether hypertension further enhances aging-induced augmented BP response to ischemic dynamic exercise has not yet been investigated. Therefore, we aimed to test the hypothesis that hypertension exacerbates the pressor response to ischemic dynamic exercise in older adults. The participants were classified into the following two groups: nonhypertensive (NHT, n = 13, 60-80 years) and hypertensive (HT, n = 10, 61-78 years). We compared the BP responses to very light-intensity rhythmic handgrip exercise during post-isometric handgrip exercise muscle ischemia (PEMI) simulated as ischemic dynamic exercise between the HT and NHT groups. Both systolic BP (SBP) and diastolic BP (DBP) responses to the rhythmic handgrip exercise during PEMI in the HT group (∆SBP: 48 ± 18 mmHg and ∆DBP: 28 ± 10 mmHg, p = 0.007) were significantly higher than those in the NHT group (∆SBP: 34 ± 17 mmHg and ∆DBP: 20 ± 6 mmHg, p = 0.003). Importantly, resting SBP was a significant independent determinant of DBP response to the rhythmic handgrip exercise during PEMI (β = 0.412, p = 0.047). These results suggest that hypertension further elevates the heightened BP response to ischemic dynamic exercise in older adults.

Keywords: arterial baroreflex; central command; exercise pressor reflex; muscle mechanoreflex; muscle metaboreflex.

FIGURE 1

Comparisons of SBP, DBP, and HR responses (Δ) between the hypertensive (HT) and nonhypertensive (NHT) groups from baseline to the isometric handgrip exercise as well as rest, passive wrist movement, and rhythmic handgrip exercise during post‐exercise muscle ischemia (PEMI). DBP, diastolic blood pressure; HR, heart rate; HT, hypertensive; NHT, nonhypertensive; SBP, systolic blood pressure. Data were tested using a linear mixed model. Cohen's f ² was used as the effect size (0.02, 0.15, and 0.35 for small, medium, and large, respectively). Values are means. The NHT older adults were selected from our previous study (Hasegawa et al., 2021). The baseline values are shown as SBP, DBP, and HR at rest in Table 1. Detailed post hoc comparisons among stimulation modes are provided in Table S1. *The SBP response during isometric handgrip exercise rarely falls below zero (Wakeham et al., 2023), raising the question of whether this occurrence was due to a technical artifact or a genuine physiological response. Although these data exceeded the mean of −1.96 SD, they were not identified as significant outliers according to the Smirnov–Grubbs test (p = 0.091). Even if these data were excluded, the statistical results remained unchanged (Group effect: p = 0.020 [f ²  = 0.199], Stim mode effect: p < 0.001 [f ²  = 1.225], interaction: p = 0.036 [f ²  = 0.041], and Post hoc: Isometric handgrip exercise, p = 0.015; rest during PEMI, p = 0.013; passive movement during PEMI, p = 0.075; and rhythmic handgrip exercise during PEMI, p = 0.006).