The acute and chronic effects of high-intensity exercise in hypoxia on blood pressure and post-exercise hypotension: A randomized cross-over trial

The Relationship between Postexercise Hypotension and Heart Rate Variability before and after Exercise Training

Because data are scarce, we examined the relationship between postexercise hypotension (PEH) and heart rate variability (HRV) before and after aerobic exercise training among adults with hypertension. Participants completed a 12 w aerobic training program. Before and after training, they performed a peak graded exercise stress test (GEST) and nonexercise control (CONTROL) and were left attached to an ambulatory BP monitor. Prior to CONTROL, HRV was measured supine for 5 min using a 12-lead electrocardiogram (ECG). The participants (n = 18) were middle-aged (52.1 ± 11.7 y) and 50% men with hypertension (131.7 ± 9.8/85.9 ± 8.5 mmHg) and obesity (30.0 ± 3.7 kg·m^-2). Before training, ambulatory systolic BP (ASBP) and diastolic ABP (ADBP) decreased by 3.2 ± 2.1 mmHg and 2.5 ± 1.5 mmHg, respectively, from baseline after the GEST versus CONTROL (p < 0.05). After training, ASBP tended to decrease by 3.5 ± 2.2 mmHg (p = 0.055) and ADBP decreased by 1.7 ± 2.5 mmHg (p = 0.001) from baseline after the GEST versus CONTROL. Before training, HRV high frequency (HFms²) (β = -0.441), age (β = 0.568), and resting SBP (β = 0.504) accounted for 66.8% of the ASBP response (p = 0.001), whereas the low frequency (LF)/HF ratio (β = 0.516) and resting DBP (β = 0.277) accounted for 35.7% of the ADBP response (p = 0.037). After training, the standard deviation of NN intervals (SDNN) (β = -0.556), age (β = 0.506), and resting SBP (β = 0.259) accounted for 60.7% of the ASBP response (p = 0.004), whereas SDNN (β = -0.236) and resting DBP (β = 0.785) accounted for 58.5% of the ADBP response (p = 0.001). Our preliminary findings show that adults with hypertension and parasympathetic suppression (i.e., lower SDNN and HFms² and higher LF/HF) may elicit PEH to the greatest degree independent of training status versus adults with parasympathetic predominance, suggesting that resting HRV may be an important determinant of PEH.

HIGH-INTENSITY INTERVAL TRAINING POSES NO RISK TO HYPERTENSIVE WOMEN

ABSTRACT Introduction: The aim of this study was to evaluate whether a single session of high-intensity interval training (HIIT) would promote a hypotensive effect and cardiovascular risk in hypertensive women, in addition to increasing the bioavailability of nitric oxide. Methods: The sample consisted of 10 hypertensive women (63.7 ± 10.34 years; 66 ± 7.67 kg and 153.7 ± 9.08 cm) and the training load was established at 60% of the maximum aerobic speed. Results: We observed a very high hypotensive effect between the interaction moments during the intervention (Int. Pre: 122.40 ± 18.58; Int. Post: 143.00 ± 24.90; Int. Post 60min: 121.40 ± 13.87; p<0.001, η2P = 0.569). No cardiovascular risk was observed during the intervention (DP = Int. Pre: 9138.20 ± 1805.34; Int. Post: 14849.70 ± 3387.94; Int. Post 60min: 9615.90 ± 1124.41, p< 0.001, η2P = 0.739) and there was no increase in the bioavailability of nitric oxide. Conclusion: In conclusion, this work reveals that an HIIT session is capable of generating a hypotensive effect while not posing cardiovascular risk in hypertensive women. Level of evidence I; High-quality randomized clinical trial with or without statistically significant difference, but with narrow confidence intervals .

Comparisons Between Normobaric Normoxic and Hypoxic Recovery on Post-exercise Hemodynamics After Sprint Interval Cycling in Hypoxia

The aim of this study was to investigate the effects of either normoxic or hypoxic recovery condition on post-exercise hemodynamics after sprint interval leg cycling exercise rather than hemodynamics during exercise. The participants performed five sets of leg cycling with a maximal effort (30 s exercise for each set) with a 4-min recovery of unloaded cycling between the sets in hypoxia [fraction of inspired oxygen (FiO₂) = 0.145]. The load during pedaling corresponded to 7.5% of the individual’s body weight at the first set, and it gradually reduced from 6.5 to 5.5%, 4.5, and 3.5% for the second to fifth sets. After exercise, the participants rested in a sitting position for 30 min under normoxia (room-air) or hypoxia. Mean arterial pressure decreased over time during recovery (p < 0.001) with no condition and interaction effects (p > 0.05). Compared to pre-exercise values, at 30 min after exercise, mean arterial pressure decreased by 5.6 ± 4.8 mmHg (mean ± standard deviation) during hypoxic recovery, and by 5.3 ± 4.6 mmHg during normoxic recovery. Peripheral arterial oxygen saturation (SpO₂) at all time points (5, 10, 20, and 30 min) during hypoxic recovery was lower than during normoxic recovery (all p < 0.05). The area under the hyperemic curve of tissue oxygen saturation (StO₂) at vastus lateralis defined as reperfusion curve above the baseline values during hypoxic recovery was lower than during normoxic recovery (p < 0.05). Collectively, post-exercise hypotension after sprint interval leg cycling exercise was not affected by either normoxic or hypoxic recovery despite marked differences in SpO₂ and StO₂ during recovery between the two conditions.

Post-exercise hypotensive response in stroke patients following acute moderate or high intensity cycling session

BACKGROUND

Hypertension is highly prevalent in stroke patients and reducing blood pressure is a priority. Aerobic exercise is known to induce post-exercise hypotensive responses, but limited studies have documented this concept in stroke patients. The purpose was to investigate the effect of a single bout of moderate intensity continuous training (MICT) and high intensity interval training (HIIT) on post-exercise ambulatory blood pressure with patients with prior ischemic stroke or transient ischemic attack (TIA).

METHODS

Ten hypertensive adults (mean age: 70 ± 9 years) with prior ischemic stroke or TIA participated using a randomized crossover design. Ambulatory blood pressure was monitored for up to 8 hours after isocaloric either ergocycle MICT or HIIT of respectively 50% and 95% of peak power output. Blood pressure was compared to pre-exercise resting measure.

RESULTS

HIIT and MICT induced a decrease of systolic blood pressure of -11.0 ± 9.2 mmHg and -4.7 ± 4.5 mmHg respectively (p= 0.03) immediately after the exercise. Ambulatory systolic blood pressure showed a steady linear increase (R2 = 0.90; p< 0.001) of ~1.2 mmHg/hour and returned to pre-exercise measure after 8 hours. Effect of the two exercise conditions over time did not significantly differ (p= 0.278). Diastolic blood pressure was not affected by both exercises.

CONCLUSIONS

Those results suggest that HIIT induce a systolic blood pressure reduction of greater magnitude than MICT immediately after cycling exercise among patients with prior ischemic stroke or TIA. For both exercises, effects on ambulatory blood pressure are similar and persist up to 8 hours.

High-intensity exercise in hypoxia improves endothelial function via increased nitric oxide bioavailability in C57BL/6 mice

Aim

The optimal exercise intensity to improve endothelial function remains unclear, as well as whether the addition of hypoxia could potentiate this function. Therefore, the aim of this study was to compare the effects of different exercise intensities in normoxia and hypoxia on vascular reactivity and nitric oxide (NO) bioavailability in mice.

Methods

C57BL/6 mice underwent treadmill running three times per week, for 4 weeks at either low, maximal or supramaximal intensity in normoxia or hypoxia (inspire oxygen fraction = 0.13). Vascular reactivity and expression of genes and proteins involved in NO production/bioavailability were assessed in aorta using isolated vessel tension experiments, RT‐qPCR and western blot, respectively. Circulating NO metabolites and pro‐/antioxidant markers were measured.

Results

Hypoxic exercise improved both acetylcholine‐induced vasorelaxation and phenylephrine‐induced vasoconstriction compared to normoxic exercise, independently of intensity. In hypoxia, a higher acetylcholine‐induced vasorelaxation was observed with high intensities (supramaximal and maximal) compared to low intensity. Exercise protocols modulated endothelial nitric oxide synthase (eNOS) and α1‐adrenergic receptor (α₁‐AR) mRNA level, but not superoxide dismutase 3 (SOD3) and p47phox. No significant differences were observed for protein expression of α₁‐AR, total eNOS, phosphorylated eNOS, SOD isoforms and p47phox. However, plasma SOD and catalase activities were significantly increased in hypoxic supramaximal compared to hypoxic low intensity, while concentration of nitrotyrosine significantly decreased. The latter was also observed in hypoxic maximal and supramaximal compared to the same intensities in normoxia.

Conclusion

Hypoxic high‐intensity exercise increases NO bioavailability and improves vascular function, opening promising clinical perspectives for cardiovascular disease prevention.

Acute exercise-induced changes in cardiac function relates to right ventricular remodeling following 12-wk hypoxic exercise training

Repeated ventricular exposure to alterations in workload may relate to subsequent cardiac remodeling. We examined whether baseline acute changes in right (RV) and left ventricular (LV) function relate to chronic cardiac adaptation to 12-wk exercise training. Twenty-one healthy individuals performed 12-wk high-intensity endurance running training under hypoxia (fraction of inspired oxygen: 14.5%). Resting transthoracic echocardiography was performed before and after the training program to assess ventricular structure, function, and mechanics (including strain-area/volume loops). In addition, we examined systolic cardiac function during recumbent exercise under hypoxia at baseline (heart rate of 110-120 beats/min, "stress echocardiography"). Fifteen individuals completed training (22.0 ± 2.4 yr, 10 males). Hypoxic exercise training increased RV size, including diameter and area (all P < 0.05). With exception of an increase in RV fractional area change (P = 0.03), RV function did not change post-training (all P > 0.05). Regarding the RV strain-area loop, lower systolic and diastolic slopes were found post-training (P < 0.05). No adaptation in LV structure, function, or mechanics was observed (all P > 0.05). To answer our primary aim, we found that a greater increase in RV fractional area change during baseline stress echocardiography (r = -0.67, P = 0.01) inversely correlated with adaptation in RV basal diameter following 12-wk training. In conclusion, 12-wk high-intensity running hypoxic exercise training induced right-sided structural remodeling, which was, in part, related to baseline increase in RV fractional area change to acute exercise. These data suggest that acute cardiac responses to exercise may relate to subsequent RV remodeling after exercise training in healthy individuals.NEW & NOTEWORTHY During exercise, the right ventricle is exposed to a disproportionally higher wall stress than the left ventricle, which is further exaggerated under hypoxia. In this study, we showed that 12-wk high-intensity running hypoxic exercise training induced right-sided structural remodeling, which was, in part, related to baseline cardiac increase in RV fractional area change to acute exercise. These data suggest that acute RV responses to exercise are related to subsequent right ventricular remodeling in healthy individuals upon hypoxic training.

Impact of High Altitude on Cardiovascular Health: Current Perspectives

Globally, about 400 million people reside at terrestrial altitudes above 1500 m, and more than 100 million lowlanders visit mountainous areas above 2500 m annually. The interactions between the low barometric pressure and partial pressure of O2, climate, individual genetic, lifestyle and socio-economic factors, as well as adaptation and acclimatization processes at high elevations are extremely complex. It is challenging to decipher the effects of these myriad factors on the cardiovascular health in high altitude residents, and even more so in those ascending to high altitudes with or without preexisting diseases. This review aims to interpret epidemiological observations in high-altitude populations; present and discuss cardiovascular responses to acute and subacute high-altitude exposure in general and more specifically in people with preexisting cardiovascular diseases; the relations between cardiovascular pathologies and neurodegenerative diseases at altitude; the effects of high-altitude exercise; and the putative cardioprotective mechanisms of hypobaric hypoxia.

Post-exercise cardiac autonomic and cardiovascular responses to heart rate-matched and work rate-matched hypoxic exercise

Purpose

This study investigated the effect of performing hypoxic exercise at the same heart rate (HR) or work rate (WR) as normoxic exercise on post-exercise autonomic and cardiovascular responses.

Methods

Thirteen men performed three interval-type exercise sessions (5 × 5-min; 1-min recovery): normoxic exercise at 80% of the WR at the first ventilatory threshold (N), hypoxic exercise (FiO₂ = 14.2%) at the same WR as N (H-WR) and hypoxic exercise at the same HR as N (H-HR). Autonomic and cardiovascular assessments were conducted before and after exercise, both at rest and during active squat–stand manoeuvres (SS).

Results

Compared to N, H-WR elicited a higher HR response (≈ 83% vs ≈ 75%HRmax, p < 0.001) and H-HR a reduced exercise WR (− 21.1 ± 9.3%, p < 0.001). Cardiac parasympathetic indices were reduced 15 min after exercise and recovered within 60 min in N and H-HR, but not after H-WR (p < 0.05). H-WR altered cardiac baroreflex sensitivity (cBRS) both at rest and during SS (specifically in the control of blood pressure fall during standing phases) in the first 60 min after the exercise bout (p < 0.05). Post-exercise hypotension (PEH) did not occur in H-HR (p > 0.05) but lasted longer in H-WR than in N (p < 0.05).

Conclusions

Moderate HR-matched hypoxic exercise mimicked post-exercise autonomic responses of normoxic exercise without resulting in significant PEH. This may relate to the reduced WR and the limited associated mechanical/metabolic strain. Conversely, WR-matched hypoxic exercise impacted upon post-exercise autonomic and cardiovascular responses, delaying cardiac autonomic recovery, temporarily decreasing cBRS and evoking prolonged PEH.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00421-021-04678-5.