Acute Response to a 2-Minute Isometric Exercise Test Predicts the Blood Pressure-Lowering Efficacy of Isometric Resistance Training in Young Adults

Effects of a maintenance period on ambulatory blood pressure and morning blood pressure surge in young normotensives post isometric training

Isometric resistance training (IRT) has emerged as an efficacious therapeutic intervention to reduce ambulatory blood pressure (BP), and BP diurnal variability. However, once the required decreases in BP have been achieved the efficacy of implementing a reduced maintenance dose is not understood. Therefore, the purpose of this study was to determine the effects of an 8-week maintenance period (8-week) following the cessation of the prescribed 8-week IRT in young normotensives. Twenty-two recreationally active, not resistance trained, normotensive (24-h ambulatory SBP, ≥130 mmHg) young adults were randomly assigned to a training-maintenance [TG-MT; n = 13 (female = 5); age 21 ± 2 years] or a non-training control [CON; n = 9 (female = 4); age 23 ± 3 years] group. Ambulatory BP, morning BP surge (MBPS) and average real variability (ARV) were measured prior to, after 8 weeks of bilateral leg IRT (4x2-minute contractions at 20% MVC with 2-min rest periods, 3 days/week) and following an 8-week (once per week) maintenance period. On completion of the maintenance period the significant reductions seen following the IRT were maintained within the TG-MT group in 24-h ambulatory SBP (6 ± 4 mmHg, p < 0.001), daytime (5 ± 5 mmHg, p = 0.002), MBPS (7 ± 10 mmHg, p = 0.019) and 24-h SBP ARV (2.03 ± 1.44 mmHg, p = 0.001), daytime SBP ARV (2.04 ± 1.78 mmHg, p = 0.003). These results show that reductions in ambulatory BP (24-h SBP and daytime SBP), in addition to BP diurnal variations (MBPS, 24-h SBP ARV and daytime SBP AVR) are maintained following an 8-week maintenance dose in young adults and add further weight to the growing body of evidence promoting IRT as an efficacious therapeutic exercise intervention to prevent or reduce BP.

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.

Getting the best GRIP on blood pressure control: Investigating a cost-effective isometric handgrip alternative

OBJECTIVES

The World Health Organization emphasises the need for cost-effective alternative methods to lower blood pressure (BP). Endorsed nationally in HTN guidelines, isometric handgrip (IHG) training is an alternative method of BP control. The purpose of this study was to compare the BP, heart rate (HR) and rates of perceived exertion (RPE) responses between a bout of IHG training performed using the traditional computerized device and a more affordable, inflatable stress ball.

METHODS

Twenty healthy adults performed one bout (4, 2-min isometric contractions, with 1-min rests between each contraction at 30% maximal voluntary contraction) of IHG training using the traditional computerized device, and one bout with the inflatable stress ball. BP, HR, and RPE were recorded.

RESULTS

No statistically significant differences between devices were observed with HR, BP, and RPE (p < 0.05). However, average RPE for both devices ranged between 5 and 6 indicating that participants were rating 30% of their MVC, consistent with previous work.

DISCUSSION

The similar cardiovascular and psychophysical responses provide support for the potential use of this low individual- and provider-burden, cost-efficient IHG device, and lay the foundation for a future training study to test the hypothesis of benefit.

The effect of a single session of isometric handgrip exercise on blood pressure

BACKGROUND: It is unknown whether a session of isometric handgrip (IHG) exercise can influence the blood pressure of hypertensive and normotensive individuals. OBJECTIVE: To compare post exercise hypotension among groups with different resting blood pressure (BP) levels. METHODS: 56 Malay male volunteers (12 normotensive, 14 pre-hypertensive, 19 hypertensive stage 1, and 11 hypertensive stage 2) completed four sets of 2-minute isometric handgrip exercises at 30% of their maximum handgrip contraction with a one-minute break between the sets. Systolic BP (SBP), diastolic BP (DBP), pulse pressure (PP), mean arterial pressure (MAP), resting heart rate (RHR), and handgrip strength (HGS) were measured before and after an hour of IHG exercise. A paired sample t-test, one-way ANOVA, and two-way repeated measure ANCOVA were used to examine the data. RESULTS: All parameters, except RHR and HGS, were significantly changed following the exercise across the BP groups. The SBP, MAP, and HGS were greatly reduced among hypertensive stage 1 (SBP =-6.3 ± 0.6 mmHg; MAP =-4.8 ± 1.1 mmHg; HGS =-6.8 ±-0.4 mmHg) compared to other groups. Meanwhile, the most DBP was reduced among hypertensive stage 2 (mean =-5.2 ± 0.6 mmHg). CONCLUSIONS: The current study discovered a significant reduction in BP among hypertensive stage 1 and 2 individuals after a session of IHG exercise.

Sources of automatic office blood pressure measurement error: a systematic review

OBJECTIVE

Accurate and reliable blood pressure (BP) measurement is important for the prevention and treatment of hypertension. The oscillometric-based automatic office blood pressure measurement (AOBPM) is widely used in hospitals and clinics, but measurement errors are common in BP measurements. There is a lack of systematic review of the sources of measurement errors.

APPROACH

A systematic review of all existing research on sources of AOBPM errors. A search strategy was designed in six online databases, and all the literature published before October 2021 was selected. Those studies that used the AOBPM device to measure BP from the upper arm of subjects were included.

MAIN RESULTS

A total of 1365 studies were screened, and 224 studies were included in this final review. They investigated 22 common error sources with clinical AOBPM. Regarding the causes of BP errors, this review divided them into the following categories: the activities before measurement, patient's factors, measurement environment, measurement procedure, and device settings. 13 sources caused increased systolic and diastolic BP (SBP and DBP), 2 sources caused the decrease in SBP and DBP, only 1 source had no significant effect on BPs, and the other errors had a non-uniform effect (either increase or decrease in BPs). The error ranges for SBP and DBP were -14 to 33 mmHg and -6 to 19 mmHg, respectively.

SIGNIFICANCE

The measurement accuracy of AOBPM is susceptible to the influence of measurement factors. Interpreting BP readings need to be treated with caution in clinical measurements. This review made comprehensive evidence for the need for standardized BP measurements and provided guidance for clinical practitioners when measuring BP with AOBPM devices.

Acute cardiac autonomic and haemodynamic responses to leg and arm isometric exercise

OBJECTIVES

Acute cardiovascular responses following a single session of isometric exercise (IE) have been shown to predict chronic adaptations in blood pressure (BP) regulation. It was hypothesised that exercises which recruit more muscle mass induce greater reductions in BP compared to exercises using smaller muscle mass. To test this hypothesis, the current study aimed to compare the acute haemodynamic and autonomic responses to a single session of isometric wall squat (IWS) and isometric handgrip (IHG) training.

METHODS

Twenty-six sedentary participants performed a single IWS and IHG session in a randomised cross-over design, with training composed of 4 × 2-min contractions, with 2-min rest, at 95 HR_peak and 30% MVC respectively. Haemodynamic and cardiac autonomic variables were recorded pre, during, immediately post, and 1-h post-exercise, with the change from baseline for each variable used for comparative analysis.

RESULTS

During IWS exercise, there was a significantly greater increase in systolic BP (P < 0.001), diastolic BP (P < 0.001), mean BP (P < 0.001), heart rate (P < 0.001), and cardiac output (P < 0.001), and a contrasting decrease in baroreflex effectiveness index (BEI) and cardiac baroreceptor sensitivity (cBRS). In the 10-min recovery period following IWS exercise, there was a significantly greater reduction in systolic BP (P = 0.005), diastolic BP (P = 0.006), mean BP (P = 0.003), total peripheral resistance (TPR) (P < 0.001), BEI (P = 0.003), and power spectral density (PSD-RRI) (P < 0.001). There were no differences in any variables between conditions 1-h post exercise.

CONCLUSIONS

Isometric wall squat exercise involving larger muscle mass is associated with a significantly greater post-exercise hypotensive response during a 10-min recovery window compared to smaller muscle mass IHG exercise. The significantly greater reduction in TPR may be an important mechanism for the differences in BP response.

The Impact of Aerobic Training on Cardiovascular Reactivity to and Recovery From Psychological and Orthostatic Challenge

OBJECTIVE

Elevated cardiovascular reactivity to, and reduced recovery from, challenging events may increase the risk of cardiovascular disease, and exercise training may reduce this reactivity. However, in a randomized controlled trial of aerobic versus strength training in sedentary, healthy young adults, we found no training group differences in reactivity or recovery. Because strength training also may have a reactivity-reducing effect, we conducted a secondary analysis of data from another trial, this time with a wait-list control condition.

METHODS

One hundred nineteen healthy, young, sedentary adults were randomized to a 12-week aerobic training program or wait-list control. Before (T1) and after (T2) training and after 4 weeks of sedentary deconditioning (T3), we measured heart rate (HR), heart rate variability, and blood pressure at rest and in response to and recovery from psychological and orthostatic challenge. Data were analyzed using a group (aerobic versus wait-list) by session (T1, T2, and deconditioning) and by period (baseline, psychological challenge, recovery, standing) three-way analysis of variance with prespecified contrasts.

RESULTS

Aerobic capacity significantly increased at T2 and decreased at T3 only in the aerobic training group. The groups did not differ on HR, heart rate variability, or blood pressure reactivity to or recovery from challenge. Without baseline adjustment, there were no significant treatment differences in response to challenges. With baseline adjustment, there were significant treatment by session effects for HR (Cohen d = 0.54, p = .002), systolic blood pressure (d = 0.44, p = .014), diastolic blood pressure (d = 0.74, p = .002), and root mean squared successive difference (d = 0.48, p = .006) reactivity from T1 to T2 only for orthostatic challenge: at T2, reactivity in the aerobic group was nonsignificantly reduced, compared with T1. In the wait-list group, reactivity significantly increased after T1.

CONCLUSIONS

This study raises further doubt about attenuation of cardiovascular reactivity or enhancement of recovery as a cardioprotective mechanism of aerobic exercise training.Clinical Trial Registration:ClinicalTrials.gov Unique identifier: NCT01335737.

Factors mediating the pressor response to isometric muscle contraction: An experimental study in healthy volunteers during lower body negative pressure

Whilst both cardiac output (CO) and total peripheral resistance (TPR) determine mean arterial blood pressure (MAP), their relative importance in the pressor response to isometric exercise remains unclear. This study aimed to elucidate the relative importance of these two different factors by examining pressor responses during cardiopulmonary unloading leading to step-wise reductions in CO. Hemodynamics were investigated in 11 healthy individuals before, during and after two-minute isometric exercise during lower body negative pressure (LBNP; -20mmHg and -40mmHg). The blood pressure response to isometric exercise was similar during normal and reduced preload, despite a step-wise reduction in CO during LBNP (-20mmHg and -40mmHg). During -20mmHg LBNP, the decreased stroke volume, and consequently CO, was counteracted by an increased TPR, while heart rate (HR) was unaffected. HR was increased during -40 mmHg LBNP, although insufficient to maintain CO; the drop in CO was perfectly compensated by an increased TPR to maintain MAP. Likewise, transient application of LBNP (-20mmHg and -40mmHg) resulted in a short transient drop in MAP, caused by a decrease in CO, which was compensated by an increase in TPR. This study suggests that, in case of reductions of CO, changes in TPR are primarily responsible for maintaining the pressor response during isometric exercise. This highlights the relative importance of TPR compared to CO in mediating the pressor response during isometric exercise.

Effects of physical therapy on blood pressure in daily clinical practice-a pilot study

[Purpose] Most exercise therapy procedures induce hemodynamic changes and could be a cardiovascular risk. This pilot study investigated factors that induce an exaggerated increase in blood pressure during exercise therapy. [Participants and Methods] We measured the blood pressure and pulse rate before and after exercise therapy for ambulation on days 1, 2, and 7 of the exercise therapy in patients (n=23; age, 69 ± 11 years) who were hospitalized for a stroke or an orthopedic surgery. [Results] Each participant's blood pressure and pulse rate were significantly increased after the exercise therapy. Regression analysis demonstrated that the increase in systolic blood pressure was independently predicted by body weight and pulse rate before the exercise therapy. In the logistic regression analysis, age and body weight were independent predictors of the exaggerated increase in systolic blood pressure (fourth quartile). [Conclusion] A significant increase in blood pressure was induced by exercise therapy. There was a correlation between systolic blood pressure increase and pulse rate before the exercise therapy. Old age or increased body weight predicts exaggerated increase in blood pressure during exercise therapy.

High cardiovascular reactivity and muscle strength attenuate hypotensive effects of isometric handgrip training in young women: A randomized controlled trial

OBJECTIVE

Isometric resistance training may reduce resting blood pressure (BP); however, the magnitude of this effect varies among individual subjects and few studies attempted to predict it. This study aimed to investigate the potential hypotensive effects of isometric training and their association with cardiovascular reactivity to acute isometric exercise and muscle strength in young women.

METHODS

In this randomized trial, twenty young women were randomly assigned to either the training (n = 10) or control (n = 10) group. Women from the training group performed unilateral isometric handgrip sessions for 8 weeks (4 × 2 min at 25% of maximal voluntary contraction [MVC]; 3 days/week). Cardiovascular reactivity to acute isometric exercise and MVC were measured at baseline. Resting BP was assessed during and after the intervention.

RESULTS

Resting systolic BP significantly lowered only in the training group. The change in resting systolic BP following an 8-week intervention was significantly associated with the systolic BP and diastolic BP reactivity to the acute exercise at baseline during set 3 and 4 (P <.05). The handgrip MVC was associated with changes in systolic BP (r = 0.79, P =.007), diastolic BP (r = 0.68, P =.032), and mean arterial pressure (r = 0.79, P =.006). These results indicated that high cardiovascular reactivity and strength attenuate the hypotensive effects following isometric training in young women.

CONCLUSIONS

The hypotensive effects following isometric training may be identified by BP reactivity to acute isometric exercise or handgrip strength in young women.

Supervised, but Not Home-Based, Isometric Training Improves Brachial and Central Blood Pressure in Medicated Hypertensive Patients: A Randomized Controlled Trial

Meta-analyses have shown that supervised isometric handgrip training reduces blood pressure in hypertensives. However, the mechanism(s) underlying these effects in medicated hypertensive patients, as well as the effects from home-based exercise training, is uncertain. The purpose of this study was to compare the effects of supervised and home-based isometric handgrip training on cardiovascular parameters in medicated hypertensives. In this randomized controlled trial, 72 hypertensive individuals (38–79 years old, 70% female) were randomly assigned to three groups: home-based, supervised isometric handgrip training or control groups. Home-based and supervised isometric handgrip training was completed thrice weekly (4 × 2 min at 30% of maximal voluntary contraction, with 1-min rest between bouts, alternating the hands). Before and after 12 weeks brachial, central and ambulatory blood pressures (BP), arterial stiffness, heart rate variability, vascular function, oxidative stress and inflammation markers were obtained. No significant (p > 0.05) effect was observed for ambulatory BP, arterial stiffness, heart rate variability, vascular function and oxidative stress and inflammatory markers in all three groups. Brachial BP decreased in the supervised group (Systolic: 132 ± 4 vs. 120 ± 3 mmHg; Diastolic: 71 ± 2 vs. 66 ± 2 mmHg, p < 0.05), whereas no significant differences were observed in the home-based (Systolic: 130 ± 4 vs. 126 ± 3 mmHg; diastolic: 73 ± 3 vs. 71 ± 3 mmHg) and control groups (p > 0.05). Supervised handgrip exercise also reduced central BP systolic (120 ± 5 vs. 109 ± 5 mmHg), diastolic (73 ± 2 vs. 67 ± 2 mmHg); and mean BP (93 ± 3 vs. 84 ± 3 mmHg), whereas no significant effects were found in the home-based (Systolic: 119 ± 4 vs. 115 ± 3 mmHg; Diastolic: 74 ± 3 vs. 71 ± 3 mmHg) and control groups (p > 0.05). In conclusion, supervised, but not home-based, isometric training lowered brachial and central BP in hypertensives.