Effect of Lower- versus Higher-Intensity Isometric Handgrip Training in Adults with Hypertension: A Randomized Controlled Trial

Abstract

This study compared the effects of lower- versus higher-intensity isometric handgrip exercise on resting blood pressure (BP) and associated clinical markers in adults with hypertension. Thirty-nine males were randomly assigned to one of three groups, including isometric handgrip at 60% maximal voluntary contraction (IHG-60), isometric handgrip at 30% IHG-30, or a control group (CON) that had been instructed to continue with their current activities of daily living. The volume was equated between the exercise groups, with IHG-60 performing 8 × 30-s contractions and IHG-30 performing 4 × 2-min contractions. Training was performed three times per week for 8 weeks. Resting BP (median [IQR]), flow-mediated dilation, heart rate variability, and serum markers of inflammation and oxidative stress were measured pre- and post-intervention. Systolic BP was significantly reduced for IHG-60 (−15.5 mmHg [−18.75, −7.25]) and IHG-30 (−5.0 mmHg [−7.5, −3.5]) compared to CON (p < 0.01), but no differences were observed between both the exercise groups. A greater reduction in diastolic BP was observed for IHG-60 (−5.0 mmHg [−6.0, −4.25] compared to IHG-30 (−2.0 mmHg [−2.5, −2.0], p = 0.042), and for both exercise groups compared to CON (p < 0.05). Flow-mediated dilation increased for both exercise groups versus CON (p < 0.001). IHG-30 had greater reductions in interleukin-6 and tumor necrosis factor-α compared to the other groups (p < 0.05) and CON (p = 0.018), respectively. There was a reduction in Endothelin-1 for IHG-60 compared to CON (p = 0.018). Both the lower- and higher-intensity IHG training appear to be associated with reductions in resting BP and improvements in clinical markers of inflammation and oxidative stress.

Isometric Exercise Training and Arterial Hypertension: An Updated Review

“…Unfortunately, there are otherwise limited data on longitudinal adherence to IET, which remains a fundamental gap in the current literature. Data from short-term studies have reported good adherence to IET [64,66,73,77,80,84,85]. Palmeira et al [71] demonstrated an immediately concerning dropout rate of 50%; however, this value was similar to that observed in the control group (48%), which indicates factors other than IET (e.g., difficulty attending exercise sessions, city traffic, etc.)…”

“…Although numerous trials have consistently demonstrated the effectiveness of these intensities, comparative studies investigating novel protocols of variable intensity and inter-set recovery periods are needed to truly determine the optimal IET intensity prescription for the largest magnitude of effect on BP. Javidi et al [66] recently compared the traditional handgrip 30% MVC protocol (4 × 2 min) versus a novel 60% MVC protocol (8 × 30-s contractions), reporting significant resting BP reductions following both protocols, with significantly greater dBP reductions in the 60% MVC group. This work may provide promise for higher intensity, shorter contraction time IET protocols and ultimately highlights the importance of continued research into unexplored protocol variations.…”

“…Leg extension IET and handgrip IET can both be performed in either a unilateral or bilateral fashion. All studies of leg extension IET have adopted bilateral training, while the handgrip IET studies have used both unilateral [64,66,67,[72][73][74][75] and bilateral [46,47,54,71,[76][77][78][79][80] approaches. In a study directly comparing unilateral and bilateral approaches, McGowan et al [81] demonstrated that both unilateral and bilateral handgrip IET training were able to reduce the resting sBP of medicated hypertensive patients.…”

“…It is also important to consider that these traditionally recommended protocols of 4 × 2-min bouts at the discussed intensities have rarely been challenged and are largely rooted in original work from Wiley et al [41] and others (see Table 2). As such, research trials such as Javidi et al [66], which pilot new IET protocols against the traditional protocols, are to be encouraged.…”

Hypotensive effects of resistance training in treated hypertensive men: Is the systemic dynamic mode better than the isometric handgrip mode?

“…Difference in muscle volume involved did not seem to matter, because isometric resistance training of the arm has been reported to show superior effects on SBP reduction compared to that of leg (−6.9 vs. −4.2 mmHg) [4]. Recently, Javidi et al compared the hypotensive effects between groups performing isometric handgrip at 60% (IHG-60) and at 30% (IHG-30) of maximum voluntary contraction (MVC) [10]. The volume was equated between the exercise groups, with IHG-60 performing 8 × 30 s contractions and IHG-30 performing 4 × 2 min contractions/day.…”