Blood pressure lowering effects of a novel isometric exercise device following a 4-week isometric handgrip intervention

Low and high frequency isometric handgrip exercise training similarly reduce resting blood pressure in young normotensive adults: A randomised controlled trial

We investigated the effects of low and high frequency isometric handgrip exercise training (IHGT) on resting blood pressure, and the affective/perceptual responses during training. Sixty young normotensive adults were randomised to either a no-intervention control group (CON: n = 20; 12 female) or a group performing either two (LOW: n = 20; 18 female) or four (HIGH: n = 20; 13 female) sessions/week of IHGT for 4 weeks. IHGT involved 4 × 2-min holds at 30% maximal voluntary contraction using the dominant hand. Resting blood pressure was measured before and after training. Affective valence was measured during the first session of each training week. Systolic blood pressure was reduced following both LOW (adjusted mean change [95% CI]: -4.5 [-6.8, -2.2] mmHg) and HIGH (-5.3 [-7.6, -3.0] mmHg) frequency IHGT groups compared to CON (+0.5 [-1.8, 2.8] mmHg; p < 0.01), with no difference between LOW and HIGH. There were no changes in diastolic blood pressure. During the first session, affective valence decreased by 2.5 ± 2.6 units and became negative (lowest affect: -0.75 ± 1.84 units). However, affective responses improved as training progressed. Low and high frequency IHGT similarly reduce resting blood pressure in young normotensive adults. Negative affective responses in the early phase of training improve as the intervention progresses.

Arterial blood pressure regulation during prolonged isometric exercise in artistic gymnastic athletes compared to controls

BACKGROUND

The aim of this cross-sectional study was to examine the baroreflex sensitivity alterations in regulating arterial blood pressure during prolonged isometric exercise at different intensities in elite artistic gymnastic athletes compared to non-athletes.

METHODS

Fourteen young males participated in the study; 7 international level artistic gymnastics athletes and 7 physically active students inexperienced to isometric or resistance training. On two occasions, both groups performed 3 minutes of isometric handgrip exercise either at 30% or 50% of maximum voluntary contraction (MVC), in a randomized order. Force production, arterial blood pressure and baroreflex sensitivity through finger plethysmograph were continuously recorded.

RESULTS

At rest, arterial blood pressure was normal in both groups (systolic blood pressure [SBP], athletes [A]: 128±9.0 mmHg, non-athletes [NA]: 130±7.2 mmHg, P=0.62; DIA, A: 75.6±5.2, NA: 78.5±4.6, P=0.31) but baroreflex sensitivity (BRS) was higher in athletes than in non-athletes (A: 16.6±7.4, NA: 12.0±7.9, P=0.02). During prolonged isometric exercise at 30% MVC, blood pressure was similar between groups (SBP, A: 176.9±16 mmHg vs. NA: 189.5±15.1 mmHg P=0.9, diastolic blood pressure [DBP], A: 108±11 mmHg vs. NA: 118±11 mmHg, P=0.6) and BRS was still higher in athletes (A: 13.28±5.75 ms/mmHg vs. NA: 6.72±3.83, P=0.04), whereas at 50% MVC, blood pressure was lower in the athletes compared to the control group (SBP, A: 182.5±15 mmHg vs. NA: 222.1±19.3 mmHg, P=0.001; DBP A: 115±14 mmHg vs. NA: 141±20 mmHg, P=0.02,without statistically significant difference in BRS between groups (A: 7.39±5.34 ms/mmHg vs. NA: 3.9±1.73 ms/mmHg, P=0.44).

CONCLUSIONS

The results of our cross-sectional study revealed that after years of exposure in high amounts of training loads, baroreflex sensitivity is increased in healthy athletes probably in order to prevent excessive increases in blood pressure during exercise.

Experiences, acceptability and feasibility of an isometric exercise intervention for stage 1 hypertension: embedded qualitative study in a randomised controlled feasibility trial

BACKGROUND

Healthy lifestyle changes for patients with stage 1 hypertension are recommended before antihypertensive medication. Exercise has antihypertensive benefits; however, low adoption and high attrition are common. Patients need easily adoptable, effective and manageable exercise interventions that can be sustained for life. We present participant and stakeholder perceptions of an isometric exercise intervention for stage 1 hypertension delivered in the National Health Service (NHS, UK).

METHODS

An embedded qualitative study within a randomised-controlled feasibility study included intervention arm participants (n = 10), healthcare professionals from participating NHS sites (n = 3) and non-participating NHS sites (n = 5) taking part in semi-structured interviews to explore feasibility of delivering an isometric exercise intervention within the study design and an NHS context. Data was analysed using reflective thematic analysis.

RESULTS

Three themes were identified: study deliverability; motivators and barriers; support for study participation. Findings indicated that the study was well designed. Health benefits, unwillingness to take medication, altruism and interest in the study helped motivation and adherence. Study support received was good, but healthcare professionals were insecure in intervention delivery with regular training/supervision needed. Perception of health improvement was mixed, but, in some, uptake of wider lifestyle changes resulted from participation. Stakeholders felt that current service challenges/demand would make implementation challenging.

CONCLUSIONS

Despite participant positivity, delivery of an isometric intervention in an NHS setting was considered challenging given the current service demand, although possible with robust effectiveness evidence. Findings support further effectiveness data and implementation development of the isometric exercise intervention.

TRIAL REGISTRATION

ISRCTN, ISRCTN13472393 . Registered 18 September 2020.

Isometric Exercise Training and Arterial Hypertension: An Updated Review

Hypertension is recognised as a leading attributable risk factor for cardiovascular disease and premature mortality. Global initiatives towards the prevention and treatment of arterial hypertension are centred around non-pharmacological lifestyle modification. Exercise recommendations differ between professional and scientific organisations, but are generally unanimous on the primary role of traditional aerobic and dynamic resistance exercise. In recent years, isometric exercise training (IET) has emerged as an effective novel exercise intervention with consistent evidence of reductions in blood pressure (BP) superior to that reported from traditional guideline-recommended exercise modes. Despite a wealth of emerging new data and endorsement by select governing bodies, IET remains underutilised and is not widely prescribed in clinical practice. This expert-informed review critically examines the role of IET as a potential adjuvant tool in the future clinical management of BP. We explore the efficacy, prescription protocols, evidence quality and certainty, acute cardiovascular stimulus, and physiological mechanisms underpinning its anti-hypertensive effects. We end the review with take-home suggestions regarding the direction of future IET research.

One year of isometric exercise training for blood pressure management in men: a prospective randomized controlled study

OBJECTIVE

Isometric exercise training (IET) over 4-12 weeks is an effective antihypertensive intervention. However, blood pressure (BP) reductions are reversible if exercise is not maintained. No work to date has investigated the long-term effects of IET on resting BP.

METHODS

We randomized 24 unmedicated patients with high-normal BP to a 1-year wall squat IET intervention or nonintervention control group. Resting BP and various clinically important haemodynamic variables, including heart rate (HR), stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) were measured pre and post the 1-year study period.

RESULTS

One year of IET produced statistically significant reductions in resting systolic (-8.5 ± 5 mmHg, P  < 0.001) and diastolic (-7.3 ± 5.8 mmHg, P  < 0.001) BP compared with the control group. There was also a significant reduction in resting HR (-4.2 ± 3.7 b/min, P  = 0.009) and a significant increase in SV (11.2 ± 2.8 ml, P  = 0.012), with no significant change in CO (0.12 ± 2.8 l/min, P  = 0.7). TPR significantly decreased following IET (-246 ± 88 dyne·s/cm 5 , P  = 0.011). Adherence to the IET sessions was 77% across all participants (3x IET sessions per week), with no participant withdrawals.

CONCLUSION

This novel study supports IET as an effective long-term strategy for the management of resting BP, producing clinically important, chronic BP adaptations in patients at risk of hypertension. Importantly, this work also demonstrates impressive long-term adherence rates, further supporting the implementation of IET as a means of effective BP management in clinical populations.

Mechanisms for blood pressure reduction following isometric exercise training: a systematic review and meta-analysis

OBJECTIVE

Isometric exercise training (IET) is established as an effective antihypertensive intervention. Despite this, the physiological mechanisms driving blood pressure (BP) reductions following IET are not well understood. Therefore, we aimed to perform the first meta-analysis of the mechanistic changes measured following IET.

METHODS

PubMed, Cochrane library and SPORTDiscus were systematically searched for randomized controlled trials published between January 2000 and December 2021 reporting the effects of IET on resting BP and at least one secondary mechanistic parameter following a short-term intervention (2-12 weeks).

RESULTS

Eighteen studies with a pooled sample size of 628 participants were included in the final analysis. IET produced significant reductions in resting systolic and diastolic BP of 9.35 mmHg (95% confidence interval [CI] = -7.80 to -10.89, P  < 0.001) and 4.30 mmHg (CI = -3.01 to -5.60, P  < 0.001), respectively. Mechanistically, IET produced a statistically significant reduction in resting heart rate (mean difference [MD]: -1.55 bpm, CI = -0.14 to -2.96, P  = 0.031) and a significant increase in stroke volume (MD: 6.35 ml, CI = 0.35 to 12.60, P  = 0.038), with no significant change in cardiac output. Conversely, total peripheral resistance (TPR) significantly decreased following IET (MD: -100.38 dyne s -1 cm 5 , CI = -14.16 to -186.61, P  = 0.023), with significant improvements in the low frequency to high frequency heart rate variability ratio (MD: -0.41, CI = -0.09 to -0.73, P  = 0.013) and baroreceptor reflex sensitivity (MD: 7.43 ms/mmHg, P  < 0.001).

CONCLUSION

This work demonstrates that a reduction in TPR, potentially mediated through enhanced autonomic vasomotor control, is primarily responsible for BP reductions following IET. Furthermore, this novel analysis suggests wall squat interventions to be the most effective IET mode, with clinically relevant differences in BP reductions compared to handgrip and leg extension IET; although future direct comparative research is required.

Safety, efficacy and delivery of isometric resistance training as an adjunct therapy for blood pressure control: a modified Delphi study

Uncontrolled hypertension remains the major risk factor for cardiovascular disease. Isometric resistance training (IRT) has been shown to be a useful nonpharmacological therapy for reducing blood pressure (BP); however, some exercise physiologists and other health professionals are uncertain of the efficacy and safety of IRT. Experts' consensus was sought in light of the current variability of IRT use as an adjunct treatment for hypertension. An expert consensus-building analysis (Delphi study) was conducted on items relevant to the safety, efficacy and delivery of IRT. The study consisted of 3 phases: (1) identification of items and expert participants for inclusion; (2) a two-round modified Delphi exercise involving expert panelists to build consensus; and (3) a study team consensus meeting for a final item review. A list of 50 items was generated, and 42 international experts were invited to join the Delphi panel. Thirteen and 10 experts completed Delphi Rounds 1 and 2, respectively, reaching consensus on 26 items in Round 1 and 10 items in Round 2. The study team consensus meeting conducted a final item review and considered the remaining 14 items for the content list. A final list of 43 items regarding IRT reached expert consensus: 7/10 items on safety, 11/11 items on efficacy, 10/12 items on programming, 8/10 items on delivery, and 7/7 on the mechanism of action. This study highlights that while experts reached a consensus that IRT is efficacious as an antihypertensive therapy, some still have safety concerns, and there is also ongoing conjecture regarding optimal delivery.

Blood pressure-lowering efficacy of a 6-week multi-modal isometric exercise intervention

Isometric exercise training (IET) is an effective method for reducing resting blood pressure (BP). To date, no research studies have been conducted using multiple exercises within an IET intervention. Previous research has suggested that varied exercise programmes may have a positive effect on adherence. Therefore, this randomized controlled study aimed to investigate the BP-lowering efficacy of a multi-modal IET (MIET) intervention in healthy young adults. Twenty healthy participants were randomized to an MIET [n = 10; four women; SBP 117.9 ± 6.9 mmHg; DBP 66.3 ± 5.1 mmHg] or control (CON) group (n = 10; five women; SBP, 123.3 ± 10.4 mmHg; DBP, 77.3 ± 6.7 mmHg). The MIET group completed three sessions per week of 4, 2-min isometric contractions, with a 1-min rest between each contraction, for 6 weeks. Resting BP and heart rate (HR) were measured at baseline and post-intervention. Pre-to-post intervention within-group reductions in resting BP were observed (SBP: 5.3 ± 6.1 mmHg, DBP: 3.4 ± 3.7 mmHg, MAP: 4.0 ± 3.9 mmHg, HR: 4.8 ±6 .6 bpm), although clinically relevant (≥2 mmHg), these changes were not statistically significant. Significant (p < 0.05) between-group differences were found between the intervention and control groups, indicating that the MIET intervention has a greater BP-lowering effect compared to control. The clinically relevant post-training reductions in resting BP suggest that MIET may be a promising additional IET method for hypertension prevention. These findings; however, must be interpreted with caution due to the small sample size and the non-clinical cohort.