Abstract

Purpose: This systematic review compares the effectiveness of high-intensity interval training (HIIT), moderate-intensity interval training (MIIT), and Isometric Training for hypertension management, aiming to ascertain if HIIT surpasses MIIT and Isometric Training in efficacy. Methods: Relevant studies from Medline, PsycINFO, Embase, Sport Disc, and CINAHL published from October 1, 2000, till October 1, 2023, were reviewed. Only randomized controlled trials (RCTs) and full-text reviews addressing HIIT, MIIT, and isometric training's impact on hypertension were included. Results: HIIT consistently yielded significant reductions in systolic and diastolic blood pressure. MIIT demonstrated positive cardiovascular effects, with some studies reporting blood pressure improvements. Isometric Training uniquely affected blood pressure regulation, leading to reductions in both systolic and diastolic blood pressure in select studies. Conclusion: The study affirms the efficacy of HIIT, MIIT, and Isometric Training in managing hypertension, with HIIT showing superior outcomes. Personalized exercise regimens tailored to individual preferences and fitness levels are crucial, emphasizing the importance of feasibility and adherence. Future research should investigate optimal exercise modality combinations and their long-term effects on hypertension management.

1. Introduction

Hypertension, characterized by persistently elevated blood pressure levels, stands as a paramount global health concern, exerting substantial ramifications on cardiovascular well-being. With the World Health Organization (WHO) estimating its prevalence among approximately 1.13 billion individuals worldwide, hypertension emerges as a leading contributor to the burden of cardiovascular diseases and associated complications ¹. Given its escalating prevalence and profound implications for morbidity and mortality, there arises an imperative to explore effective strategies for its management and prevention.

Exercise intervention has emerged as a cornerstone in the arsenal against hypertension, offering a non-pharmacological approach to mitigate its deleterious effects. Extensive research underscores the multifaceted benefits of exercise in hypertension management, including reductions in blood pressure, enhancement of endothelial function, and improvement of overall cardiovascular health ² Despite the well-established benefits of exercise, uncertainties persist regarding the optimal type, intensity, and duration of exercise for treating people with hypertension.

Recognizing the heterogeneity of hypertensive populations and the multifactorial nature of hypertension, there is a burgeoning interest in exploring various exercise modalities to tailor interventions to individual needs. Among these modalities, High-Intensity Interval Training (HIIT), Moderate-Intensity Interval Training (MIIT), and Isometric Training have emerged as focal points of investigation, each offering distinct mechanisms to potentially impact blood pressure regulation.

HIIT stands for High-Intensity Interval Training. It's a form of cardiovascular exercise that alternates short periods of intense anaerobic exercise with less intense recovery periods. Typically, a HIIT workout lasts anywhere from 10 to 30 minutes, though it can vary depending on the specific routine and fitness level of the individual. It’s characterized by alternating bouts of high-intensity exercise and periods of rest or low-intensity activity, has garnered attention for its efficiency and purported cardiovascular benefits. Studies suggest that HIIT elicits favorable changes in blood pressure by enhancing endothelial function, stimulating nitric oxide production, and improving cardiovascular fitness ³. Meanwhile, Moderate-intensity interval training (MIIT) is a variation of interval training that involves alternating periods of moderate-intensity exercise with periods of rest or lower-intensity activity. Unlike high-intensity interval training (HIIT), which involves short bursts of very intense exercise followed by brief rest periods, MIIT focuses on maintaining a moderate level of effort throughout the workout. MIIT represents a nuanced approach, combining moderate-intensity exercise with intervals of rest. Its potential lies in enhancing arterial compliance and mitigating sympathetic nervous system activity, thereby contributing to blood pressure regulation ⁴ Isometric Training, involving static muscle contractions, presents a novel avenue for hypertension management. Recent research suggests that isometric exercises may modulate blood pressure regulation through enhanced baroreflex sensitivity and reduced peripheral vascular resistance ⁵

Despite the growing body of evidence supporting the efficacy of these exercise modalities in hypertension management, significant gaps remain in our understanding of their comparative effectiveness and underlying mechanisms of action. This comprehensive review seeks to address these gaps by comparing the effects of HIIT, MIIT, and Isometric Training on hypertension management. By elucidating their relative efficacy and exploring potential mechanisms underlying their effects, including changes in endothelial function, nitric oxide production, arterial compliance, and sympathetic nervous system activity, this study aims to provide valuable insights into personalized exercise prescriptions for hypertensive individuals. Additionally, we endeavor to assess the feasibility and adherence of each exercise modality in hypertensive populations, with the hypothesis that HIIT will demonstrate superior efficacy compared to MIIT and Isometric Training. Through rigorous academic scrutiny, this review aims to contribute to the optimization of exercise-based interventions for hypertension management, ultimately enhancing cardiovascular health outcomes for individuals worldwide.

2. Materials and Methods

This systematic review used the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) guidelines ⁶. Articles published until October 2023 were analyzed. The search and selection of articles were from October 2000 to October 2023

Search Procedures and Study Selection

Hypertension (blood pressure high OR blood pressures, high OR high blood pressure OR high blood pressures) and high intensity interval training (high intensity interval trainings OR interval training, high intensity OR interval trainings, high intensity OR training, high intensity interval OR trainings, high intensity interval OR high-intensity intermittent training OR training, high intensity intermittent OR high intensity intermittent trainings OR trainings, high intensity intermittent OR sprint interval training) and moderate intensity interval training (MIIT OR moderate intensity continuous training OR moderate intensity interval training) and isometric training (Isometric exercise OR isometric training OR training isometric) were searched in Medline, PsycINFO, Cochrane library, Sport Disc, and CINAHL databases from October 2000 to October 2023 for randomized controlled trials (RCTs), review, and full text. The detailed search strategy is shown in Table 1.

3. Literature Inclusion and Exclusion Criteria

Inclusion criteria:

(1) Study type: RCTs, non-RCT, review.

(2) Study population: adult individuals with essential hypertension and prehypertension who met the diagnostic criteria for essential hypertension. The American guidelines for the prevention and treatment of hypertension define prehypertension as systolic blood pressure (SBP) of 130-139 mm Hg and diastolic blood pressure (DBP)of 80-89mm Hg, while hypertension should an or SBP of ≥ 130 mm Hg and DBP ≥ 80 mmHg. In this study, prehypertension and hypertension were collectively referred to as hypertension.

(3) Intervention: Experimental group underwent HIIT, in which high-intensity exercise was performed between80% and 100% of the peak heart rate (HR), interspersed with intervals of light exercise which defined as physical activity that requires minimal effort and does not significantly increase heart rate or breathing rate.

(4) Outcomes: The primary outcomes were post-intervention SBP and DBP, and the secondary outcomes were HR.

Exclusion criteria were as follows: non-full text, and animal experiments; literature for which valid data could not be extracted; continuous exercise interventions of <4 weeks; and duplicate publications.

Data Collection Process

A total of 30,572 articles were found. Table 2 shows the relationship between the articles found and the databases.

Upon examination of the titles, a total of 28,409 articles were eliminated from consideration as they did not correspond to the research focus as determined by the PICOS questions. Furthermore, an extra 266 articles were discarded because they were duplicates. There were 28,762 papers remaining for abstract evaluation. After conducting an abstract assessment, a total of 28,409 items were subsequently removed. Out of the remaining pool, a total of 323 articles were chosen for complete reading. Out of these, 283 studies were removed because they involved HIIT (High-Intensity Interval Training), MIIT (Moderate-Intensity Interval Training), or isometric training regimens. Additionally, three studies did not align with the proposed theme. As a result, 14 studies were selected to be included in this systematic review. The information from these publications was then retrieved and stored in an electronic database. Figure 1 below presents the PRISMA flowchart, which has been modified to suit the specific setting of this study, allowing a thorough depiction of the procedure.

Risk of Bias in Individual Studies

The quality of the selected studies was analyzed using the Tool for the assessment of Study quality and reporting in Exercise (TESTEX) scale ²

4. Results

Through structured methodology, the search resulted in 14 studies eligible for this systematic review. Table 3 contains the risk of bias within the studies.

The systematic review identified 14 studies that met the inclusion criteria, focusing on the impact of High-Intensity Interval Training (HIIT), Moderate-Intensity Interval Training (MIIT), and Isometric Training on hypertension. The studies were assessed for their quality using the Tool for the Assessment of Study Quality and Reporting in Exercise (TESTEX) scale ⁵, and the risk of bias within each study is presented in Table 3. The selected studies employed various exercise modalities, including walking, running, cycling, hand grip exercises, and squats, to investigate the effects on hypertension. The interventions in the experimental group involved HIIT, with high-intensity exercise performed between 80% and 100% of the peak heart rate (HR), interspersed with intervals of light exercise. The control group typically engaged in Moderate-Intensity Continuous Training (MICT) with an intensity of 50% to 70% of the peak HR. Additionally, isometric training with an intensity of 50% to 70% MVC was included in some studies.

The primary outcomes evaluated were post-intervention SBP and DBP, with heart rate considered as secondary outcomes.

Initially, 30,572 articles were screened, and 14 studies were selected following strict adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, as depicted in Figure 1.

The results of the selected studies varied regarding the impact of HIIT, MIIT, and Isometric Training on hypertension. Most studies reported significant reductions in both SBP and DBP post-HIIT intervention, while others suggested similar benefits with MIIT and Isometric Training. Detailed findings from each study and overall trends will be outlined in subsequent sections.

In the following sections, the specific results of each study will be presented, detailing the effects of HIIT, MIIT, and Isometric Training on hypertension parameters, including SBP, DBP, HR, Significant, and level of attendance and completion. Additionally, a comprehensive comparison of the three exercise modalities will be provided in the conclusion section, shedding light on their relative efficacy in managing hypertension.

5. Discussion

The comparison of High intensity interval training (HIIT), Moderate intensity interval training (MIIT), and Isometric Training in managing hypertension yielded diverse findings across the selected studies. The following discussion synthesizes the key results, examines the implications, and highlights potential avenues for future research.

Effectiveness of HIIT

Several studies reported that HIIT interventions led to significant reductions in both SBP and DBP. This aligns with previous research suggesting that the alternating pattern of short bursts of intense exercise followed by periods of rest or lower-intensity activity may contribute to cardiovascular health ⁷. Many studies reported reductions in SBP (<9 mmHg) and DBP (5 <mmHg), suggesting that HIIT may improve endothelial function, increased nitric oxide production, and enhanced cardiovascular fitness ². The time efficiency of HIIT, coupled with its cardiovascular benefits, supports its potential as an effective intervention for managing hypertension.

Effectiveness of MIIT

Studies investigating MIIT also demonstrated positive effects on cardiovascular health, with improvements in SBP and DBP noted in some cases. MIIT, characterized by moderate-intensity exercise interspersed with periods of rest, represents a middle ground between traditional moderate-intensity continuous exercise and HIIT. Numerous studies reported reductions in SBP (<6mmHg) and DBP (3 <mmHg), suggesting that MIIT exercises may improve arterial compliance and reduced sympathetic nervous system activity ⁸. The observed benefits of MIIT may be attributed to MIIT's potential feasibility for individuals with varying fitness levels enhances its applicability in hypertension management.

Effectiveness of Isometric Training

Isometric Training, involving static contractions of muscles without joint movement, exhibited unique effects on blood pressure regulation. Some studies reported reductions in SBP (<6mmHg) and DBP (2<mmHg), suggesting that isometric exercises may enhance baroreflex sensitivity and reduce peripheral vascular resistance ². The distinct mechanisms of isometric training make it a valuable consideration in hypertension management, warranting further investigation.

Comparative Analysis

The comprehensive comparison of HIIT, MIIT, and Isometric Training indicates that each modality has unique advantages in managing hypertension. HIIT, with its time efficiency and cardiovascular benefits, may be particularly suitable for individuals seeking a potent and efficient exercise regimen. MIIT, offering a middle ground in intensity, stands out as a feasible option for individuals with varying fitness levels. Isometric Training, with its unique effects on blood pressure regulation, adds diversity to the exercise modalities available for hypertension management.

Feasibility and Adherence

The feasibility and adherence to each exercise modality in individuals with hypertension were important considerations. Factors such as participant preferences, fitness levels, and potential barriers to exercise adherence need further exploration to tailor interventions effectively. Understanding the preferences and challenges faced by individuals with hypertension can enhance the development of personalized exercise prescriptions.

Limitations

While this systematic review provides valuable insights, it is essential to acknowledge certain limitations. Variability in study methodologies, participant characteristics, and exercise protocols may contribute to heterogeneity in results. Additionally, the duration and intensity of the interventions, as well as the lack of long-term follow-up in some studies, pose challenges in drawing definitive conclusions.

Future Directions:

Future research should explore optimal combinations of exercise modalities, considering individualized approaches based on participant characteristics and preferences. Long-term studies with extended follow-up periods are necessary to evaluate the sustained effects of HIIT, MIIT, and Isometric Training on hypertension. Moreover, investigating the potential synergistic effects of combining these modalities could provide a more comprehensive understanding of their impact on cardiovascular health.

6. Conclusion

In conclusion, the comparison of HIIT, MIIT, and Isometric Training in managing hypertension reveals promising results for each modality. HIIT, MIIT, and Isometric Training all demonstrate efficacy in reducing blood pressure, emphasizing the importance of individual preferences and health considerations in selecting the most suitable exercise regimen. The findings underscore the need for personalized exercise prescriptions tailored to the diverse needs of individuals with hypertension. As the field continues to evolve, further research and collaborative efforts will contribute to refining exercise recommendations for hypertension management.

References