Optimizing Isometric Handgrip Training for Hypertension: Insights and Gaps in Exercise Configuration

1. Introduction

An estimated 19.8 million people died from cardiovascular diseases (CVDs) in 2022, representing approximately 32% of all global deaths [1]. Of these deaths, 85% were due to heart attack and stroke [1]. Hypertension is recognized as the leading attributable risk factor for both CVD and mortality. Globally, 1.28 billion people live with hypertension [2]. Isometric handgrip training (IHT) has been recommended as a potentially viable exercise intervention for hypertension treatment [3, 4].

Previous studies [5] have demonstrated that IHT reduces resting systolic and diastolic blood pressure by approximately 7 and 4 mmHg, respectively, after a few weeks (8–12 weeks), with the advantage that it can be performed in non‐laboratory settings [6, 7]. Although there are currently many studies on this topic, an important point is that most of them have used the same IHT protocol, consisting of four sets of 2‐min contractions performed at an intensity of 30% of maximal voluntary contraction (MVC), as determined in prior maximal isometric tests [5], with few studies analyzing alternative protocols with variations in intensity, contraction duration, and number of sets [5]. Therefore, understanding the potential role of IHT configuration beyond this commonly used protocol remains a challenge.

Despite these challenges, Lin et al. [8] conducted a systematic review and meta‐analysis to better understand the influence of IHT configuration on blood pressure in both normotensive and hypertensive populations, using meta‐regression analysis. The review included 31 randomized controlled trials, including 25 studies involving hypertensive individuals. Not surprisingly, the conclusions indicated that an “evidence‐informed” protocol might consist of four sets of 2‐min unilateral contractions at ≥ 30% MVC, performed ≤3 times per week for a minimum of eight weeks, which, as noted previously, is the most commonly studied protocol. They also suggested that intensities above 30% MVC may be equally effective in reducing blood pressure.

However, rather than indicating that this configuration is the best, the systematic review highlights that this remains a gap in the literature, as only a few studies have been specifically designed to compare different IHT configurations. For example, regarding exercise intensity, to the best of our knowledge, only the study conducted by Javidi et al. [9] has directly compared different IHT intensities. The authors reported a greater reduction in resting diastolic blood pressure in the 60% MVC group compared to the 30% MVC group (−5.0 vs. −2.0 mmHg), with no significant differences observed for systolic blood pressure. Even when considering the frequently prescribed 30% MVC, often described as low intensity, data on patients’ perceived effort indicate moderate to high ratings of perceived exertion, typically around 6 on a 0–10 scale [10], which provides a different perspective on how intensity is experienced in practice. Therefore, the literature is still far from providing solid evidence on a potential dose–response relationship with respect to intensity.

The meta‐regression analysis presented by Lin et al. [8] revealed that nearly 10% of the variance in systolic blood pressure outcomes can be explained by IHT configuration, whereas for diastolic blood pressure this influence appears to be greater, at around 40%, largely driven by the direct association with the number of sets. These findings are noteworthy, as they suggest a potential influence of training configuration on diastolic blood pressure and, consequently, on peripheral vascular resistance, one of its main determinants. These types of results pave the way for future studies to investigate not only the clinical but also the mechanistic effects of IHT on blood pressure.

Despite this, the findings appear to be strongly influenced by the limited number of available studies, as only three implemented more than four sets, and all of them presented at least four out of five concerns regarding risk of bias. Consequently, clinical applicability and overall strength of the evidence remain constrained in the current state of the art. For now, the recommendation remains unchanged: the traditional protocol (4 × 2 min at 30% MVC) continues to be the most supported approach for helping to control clinic blood pressure in hypertensive patients. Nonetheless, these emerging insights underscore the urgent need for well‐designed studies specifically aimed at examining the influence of exercise configuration, in order to optimize IHT prescriptions in the future.

Author Contributions

Raphael Mendes Ritti‐Dias, Breno Quintella Farah contributed equally to the literature review, manuscript setup, and final revision of the manuscript.

Funding

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.