Effects of handgrip exercise or inorganic nitrate supplementation on 24-h ambulatory blood pressure and peripheral arterial function in overweight and obese middle age and older adults: A pilot RCT

INTRODUCTION

Hypertension is a major contributor to the global burden of cardiovascular diseases and its prevalence increases progressively with ageing. Therefore the identification of effective, age-friendly exercise and nutritional interventions which lower blood pressure (BP) is a research priority.

OBJECTIVE

To undertake a pilot RCT examining the efficacy of isometric handgrip exercise (IHGE) and beetroot juice (a rich source of inorganic nitrate) consumption in modifying clinic and 24-h ambulatory BP (24-h ABP), peripheral arterial function and plasma asymmetric dimethylarginine (ADMA) in older overweight and obese adults.

DESIGN

Thirty middle age and older adults (62±5 years) were randomised to: (a) bilateral IHGE at 50% of maximal voluntary contraction (8 min/day), (b) 140 ml/day of concentrated beetroot juice, or (c) no-intervention (control group), for 7 days. All groups followed a standardised diet to control nitrate intake. Clinic and 24-h ABP, peripheral arterial function quantified by pulse wave velocity (PWV) and arterial volume distensibility were assessed before and after intervention.

SETTING

Clinical ageing research unit, Newcastle University.

RESULTS

At baseline, there were no between-group differences in age, handgrip strength, clinic or 24-h ABP, BMI, waist circumference, fat mass, physical activity level, energy intake or urinary and plasma nitrate concentrations. After intervention, there were no significant effects on clinic systolic and diastolic BP or 24-h ABP, PWV (p=0.54), arterial volume distensibility (p=0.89), or ADMA (p=0.45).

CONCLUSIONS

IHGE or beetroot juice consumption for 7 days did not affect BP or peripheral arterial function in overweight and obese middle age and older adults. Ageing may reduce the effects of these interventions on vascular function and studies are needed to test this hypothesis.

A single oral dose of beetroot-based gel does not improve muscle oxygenation parameters, but speeds up handgrip isometric strength recovery in recreational combat sports athletes

Although the effect of beetroot supplementation on exercise performance has been widely demonstrated to improve the performance of cyclists, runners, and swimmers, its effect on combat sports remains inconclusive. The present study assessed the effect of beetroot-based gel (BG) supplementation on maximal voluntary contraction (MVC), exercise time until fatigue (ETF), muscle O₂ saturation (SmO₂), and blood volume (tHb) in response to handgrip isotonic exercise (HIE) in recreational combat sport athletes. In a randomized, crossover, double-blind study, 14 combat sports athletes performed three sets of HIE (at 40% MVC) until fatigue after BG or nitrate-depleted gel (PLA) supplementation, in which forearm SmO₂ and tHb were continuously monitored using near-infrared spectroscopy. MVC was evaluated at baseline and 20 min after HIE. MVC values were analysed as the change from baseline values (ΔMVC). There was a significant increase accompanied by a large effect size in ΔMVC (p = 0.036, d = 0.94) after HIE in the BG condition compared to PLA. However, there were no changes in SmO₂ parameters (p> 0.05), tHb (p> 0.05) or ETF (p = 0.161) throughout the three sets of HIE. Additionally, a trivial to small effect size was observed in near-infrared spectroscopy (NIRS) parameters and ETF (d = ≤ 0.2 to 0.5). Therefore, a single dose of beetroot gel supplementation may be considered as a good nutritional strategy to improve strength recovery in combat sports athletes.

Resting blood pressure reductions following handgrip exercise training and the impact of age and sex: a systematic review and narrative synthesis

BACKGROUND

The risk of developing cardiovascular disease can be directly correlated to one's resting blood pressure (BP), age, and biological sex. Resting BP may be successfully reduced using handgrip exercise training, although the impact of age and sex on training effectiveness has yet to be systematically evaluated. The objective of this systematic review is to determine this impact of age and sex on handgrip-induced changes to resting BP.

METHODS

Data sources included MEDLINE, Embase, Cochrane Reviews, CINAHL, SPORTDiscus, Web of Science, AMED, PubMed, and Scopus through May 2018. Eligibility criteria were those with prospective handgrip exercise training of ≥ 4 weeks with reported impact on resting systolic BP (SBP). Screening of articles, data extraction, and quality appraisal were completed in duplicate. When necessary, the corresponding authors were contacted to provide segregated data based on age (younger, 18-54 years; aged, > 55 years) and sex (men, women) categories. SBP was primarily explored with numerous secondary outcomes of interest summarized as a narrative synthesis.

RESULTS

After screening 1789 articles, 26 full texts were reviewed. Eight studies reported data in a way that facilitated age and sex comparisons of primary outcomes, while 7 of 18 studies reporting pooled data (men and women) provided segregated results. Research spans 1992-2018 and represents 466 participants; at least 43.1% of whom are women. Although weighted mean differences reveal that handgrip training-induced SBP reductions are similar when merely comparing sexes (women; - 5.6 mmHg, men; - 4.4 mmHg) or ages (younger; - 5.7 mmHg, aged; - 4.4 mmHg), when the impact of sex and age is simultaneously evaluated, aged women experience the largest reduction in SBP (- 6.5 mmHg). Many factors were explored for their impact on resting BP reductions and have been summarized in the corresponding narrative synthesis.

CONCLUSIONS

Handgrip exercise is an effective modality for resting BP reduction resulting in clinically significant reductions for men and women of all ages.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42015019792.

Ramp and step increases in shear stress result in a similar magnitude of brachial artery flow-mediated dilation

PURPOSE

There is evidence that the endothelium is responsive to both the rate and magnitude of increases in shear stress. However, whether flow-mediated dilation stimulated by sustained increases in shear stress (SS-FMD) is rate sensitive in humans is unknown. The purpose of this investigation was to test whether ramp (gradual) and step (instantaneous) increases in shear stress elicit disparate SS-FMD.

METHODS

Young, healthy men (n = 18, age = 22 ± 2 years, body mass index = 25 ± 3 kg m^-2) performed two 11-min bouts of rhythmic handgrip exercise; one with a 5.5-min ramp-increase in shear stress and one with an immediate step increase in shear stress. Ramp increases in shear stress were achieved through incremental increases in handgrip exercise intensity [increases of 4% maximum voluntary contraction (MVC) every 30 s for 5.5 min, ending at 44% MVC] and step increases in shear stress were achieved through a combination of arterial compression and commencing handgrip exercise at 44% MVC.

RESULTS

Shear rate was greater in the step versus ramp protocol in minutes 1-6, but not different thereafter. Similarly, SS-FMD was greater in the step versus ramp protocol during minutes 2-6, but similar in minutes 7-11 (minute 11: ramp 8.7 ± 4.6%; step 9.4 ± 3.6%; P = 0.343). SS-FMD continued to increase over time with maintenance of a steady shear stress stimulus (step minutes 2-11: 0.51 ± 0.36% min^-1; ramp minutes 7-11: 0.64 ± 0.57% min^-1; P = 0.259).

CONCLUSIONS

These findings indicate that in the brachial artery of humans, the magnitude of SS-FMD is determined by the magnitude and duration, but not the rate, of increases in shear stress.

Sex difference in the influence of central blood volume mobilization on the exercise pressor response

PURPOSE

To determine the sex difference in the impact of central venous pressure (CVP) on the pressor response induced by ischemic handgrip exercise.

METHODS

Twelve young healthy individuals (six males, 25 ± 3 years) performed ischemic handgrip exercise during mild levels of lower body negative pressure (LBNP, -5 mmHg) and during a 10° head-down tilt (HDT) to lower and increase CVP, respectively. The protocol consisted of 3 min of baseline ischemia, followed by 2 min of isometric handgrip exercise at 35 % of maximal voluntary contraction force, and 2 min of post-exercise circulatory occlusion. Mean arterial pressure (MAP) was assessed continuously by finger plethysmography and CVP was estimated from the venous pressure of the non-exercising dependent arm.

RESULTS

Baseline CVP was greater during HDT than LBNP (8.4 ± 1.8 vs. 6.5 ± 1.8 mmHg, p < 0.01). MAP was greater during LBNP than HDT throughout the protocol (p = 0.05). During ischemic handgrip exercise, CVP increased in males but not in females (Group × protocol interaction: p = 0.01). A group × condition interaction was also observed for MAP, with males showing a greater MAP during LBNP than HDT (110 ± 2 vs. 103 ± 2 mmHg, p < 0.01).

CONCLUSIONS

Baseline CVP inversely affected the pressor response to handgrip exercise in all individuals, with a greater MAP response observed during LBNP than HDT. Increase in CVP in males may be due to a greater splanchnic vasoconstrictor response to ischemic handgrip exercise. Therefore, combined baseline CVP and changes in CVP likely contributed to the greater MAP response observed during LBNP in males.

Effect of breath-hold on the responses of arterial blood pressure and cerebral blood velocity to isometric exercise

PURPOSE

The present study examined the effect of breath-hold without a Valsalva maneuver during isometric exercise on arterial blood pressure (ABP) and cerebral blood flow (CBF).

METHODS

Twenty healthy adults (15 men and five women) randomly performed only breath-hold without a Valsalva maneuver (BH), and an isometric handgrip exercise for 30 s at 40% of individual maximal voluntary contraction with continuous breathing (IHG) and with breath-hold without the Valsalva maneuver (IHG-BH). Mean ABP (MAP) and blood velocity in the middle (MCA V_mean) and posterior cerebral arteries (PCA V_mean) were continuously measured throughout each protocol.

RESULTS

MAP was elevated during the IHG-BH compared with IHG (P < 0.001) and BH (P = 0.001). Similarly, both MCA V_mean and PCA V_mean were higher during IHG-BH compared with IHG and BH (all P < 0.001). Moreover, the relative change in MAP from the baseline was correlated with that in both cerebral blood velocities during the BH (MCA V_mean: r = 0.739, P < 0.001 and PCA V_mean: r = 0.570, P = 0.009) and IHG-BH (MCA V_mean: r = 0.755, P < 0.001 and PCA V_mean: r = 0.617, P = 0.003) condition, but not the IHG condition (P = 0.154 and P = 0.306).

CONCLUSION

These results indicate that during isometric exercise, a breath-hold enhances an exercise-induced increase in MAP and, consequently, MCA V_mean and PCA V_mean.

Inorganic nitrate supplementation and blood flow restricted exercise tolerance in post-menopausal women

Exercise tolerance appears to benefit most from dietary nitrate (NO3-) supplementation when muscle oxygen (O2) availability is low. Using a double-blind, randomized cross-over design, we tested the hypothesis that acute NO3- supplementation would improve blood flow restricted exercise duration in post-menopausal women, a population with reduced endogenous nitric oxide bioavailability. Thirteen women (57-76 yr) performed rhythmic isometric handgrip contractions (10% MVC, 30 per min) during progressive forearm blood flow restriction (upper arm cuff gradually inflated 20 mmHg each min) on three study visits, with 7-10 days between visits. Approximately one week following the first (familiarization) visit, participants consumed 140 ml of NO3- concentrated (9.7 mmol, 0.6 gm NO3-) or NO3-depleted beetroot juice (placebo) on separate days (≥7 days apart), with handgrip exercise beginning 100 min post-consumption. Handgrip force recordings were analyzed to determine if NO3- supplementation enhanced force development as blood flow restriction progressed. Nitrate supplementation increased plasma NO3- (16.2-fold) and NO2- (4.2-fold) and time to volitional fatigue (61.8 ± 56.5 s longer duration vs. placebo visit; p = 0.03). Nitrate supplementation increased the rate of force development as forearm muscle ischemia progressed (p = 0.023 between 50 and 75% of time to fatigue) with non-significant effects thereafter (p = 0.052). No effects of nitrate supplementation were observed for mean duration of contraction or relaxation rates (all p > 0.150). These results suggest that acute NO3- supplementation prolongs time-to-fatigue and speeds grip force development during progressive forearm muscle ischemia in postmenopausal women.

The effects of isometric handgrip and post-exercise circulatory occlusion on muscle sympathetic nerve activity: A systematic review and meta-analysis

This systematic review and meta-analysis was conducted to identify a 'normative' sympathetic response to isometric handgrip and post-exercise circulatory occlusion. Structured searches of databases were performed until June 2024. We included all primary studies (other than systematic reviews and meta-analyses), and inclusion criteria were: population (all populations); intervention (isometric handgrip and post-exercise circulatory occlusion); comparator (baseline); and outcome (MSNA). One-hundred fifty-eight studies (n = 3551) were included. Burst frequency was elevated during handgrip (n = 1853; MD, 12.19bursts/min; 95 % CI, 11.09, 13.28; I2 = 94 %; p < 0.00001) and during PECO (n = 948; MD, 11.42bursts/min; 95 % CI, 10.10, 12.75; I2 = 65 %; p < 0.00001). A similar pattern was observed for burst incidence in handgrip (n = 1074; MD, 8.50bursts/100 hbs; 95 % CI, 7.07, 9.93; I2 = 39 %; p < 0.00001) and PECO (n = 560; MD, 14.87bursts/100 hbs; 95 % CI, 12.65, 17.10; I2 = 43 %; p < 0.00001). Subgroup analyses indicated a larger response in burst frequency and incidence during handgrip exercise in healthy individuals compared to individuals with cardiovascular diseases or other conditions (p < 0.05). A similar response in burst frequency to PECO was observed with subgroup differences between healthy individuals and individuals with cardiovascular diseases and other conditions (p < 0.00001). MSNA is elevated during handgrip exercise across a range of handgrip protocols, populations, and co-interventions. Increases in MSNA during PECO supports the role of the metaboreflex separate to the exercise pressor reflex. A blunted sympathetic response to handgrip and PECO in individuals with cardiovascular diseases contradicts the current understanding of general sympathetic hyperactivity in these populations.

Site-specific different dynamic cerebral autoregulation and cerebrovascular response to carbon dioxide in posterior cerebral circulation during isometric exercise in healthy young men

Different cerebral blood flow (CBF) responses to exercise between the posterior cerebral artery (PCA) and vertebral artery (VA) have been previously observed, though the physiological mechanisms remain unknown. There is regional heterogeneity in sympathetic innervation between the PCA and VA, which may affect CBF regulation, especially during sympathoexcitation. Thus, in the present study, we hypothesized that different CBF regulatory mechanisms between PCA and VA contribute to heterogeneous CBF responses to isometric exercise. To test this hypothesis, in thirteen healthy young men, dynamic cerebral autoregulation (CA) and cerebrovascular CO2 reactivity (CVR), were identified in each artery during a 2-min isometric handgrip (IHG) exercise at 30% of maximum voluntary contraction. Similar to previous data, PCA cerebrovascular conductance (CVC) index was decreased from rest (P < 0.004), but not VA CVC during IHG exercise (P > 0.084). Dynamic CA in both PCA and VA were unaltered during the IHG exercise (P = 0.129). On the other hand, PCA CVR was increased during the IHG exercise (P < 0.001) while VA CVR was unchanged (P = 0.294). In addition, individual exercise-induced changes in end-tidal partial pressure of CO2 was related to the individual change in PCA blood velocity (P < 0.046), but was not observed for VA blood flow (P > 0.420). Therefore, these exercise-induced differences in CVR between PCA and VA may contribute to exercise-induced heterogeneous CBF response in the posterior cerebral circulation. These findings indicate that the site-specific posterior CBF should be considered in further research for assessing posterior cerebral circulation.

Exercise-induced dynamic mitral regurgitation is associated with outcomes in patients with ischaemic cardiomyopathy

AIMS

Ischaemic mitral regurgitation (MR) is a dynamic condition influenced by global and regional left ventricular remodelling as well as mitral valvular deformation. Exercise testing plays a substantial role in assessing the haemodynamic relevance of MR and is recommended by current guidelines. We aimed to assess the prevalence, haemodynamic consequences, and prognostic impact of dynamic MR using isometric handgrip exercise.

METHODS AND RESULTS

Heart failure patients with ischaemic cardiomyopathy and at least mild MR who underwent handgrip echocardiography at the University Hospital Duesseldorf between January 2018 and September 2021 were enrolled. Patients were followed-up for 1 year to assess a combined endpoint including all-cause mortality, heart failure hospitalization, mitral valve surgery/interventions, ventricular assist device implantation and heart transplantation. One hundred thirty-three patients with ischaemic cardiomyopathy were included (age 75 ± 10 years; 21% female; LVEF 35 ± 9%). At rest, 70 patients (53%) presented with mild MR, 54 patients had moderate MR (41%), and 9 patients (7%) showed severe MR. Twenty-five patients (20%) with non-severe MR at rest, developed severe MR during handgrip exercise. Patients with dynamic MR had larger left atrial dimensions, increased wall motion score index and larger tenting area at rest. Multivariate analysis identified MR severity during exercise [HR 1.998 (1.367-2.938)] and exercise TAPSE [HR 0.913 (0.853-0.973)] as predictors of the combined endpoint.

CONCLUSIONS

The haemodynamic changes provoked by isometric exercise unmasked dynamic severe MR in a significant number of patients with non-severe MR at rest. These data may have implications for therapeutic decision-making in symptomatic patients with non-severe MR at rest.

Immune system response to isometric handgrip exercise and effects of duration and intensity of the exercise protocol on selected immune system parameters in prehypertensives

BACKGROUND

Recent studies have shown that physical exercise significantly modulates immunocyte dynamics and possibly plays a significant role on immune function. This study examined the responses of some selected immune system parameters to isometric handgrip exercise and identified possible effects of intensity and duration of the exercise protocols.

METHODS

One hundred and ninety-two (N=192) sedentary pre-hypertensive subjects, aged between 30-50 years were recruited into the study. They were randomly distributed into three groups of 64 subjects each. A detailed explanation and a demonstration of the exercise protocol were given to the subjects and they were asked to report at the Exercise Physiology unit of the Physiotherapy department, Federal Medical Centre, Asaba, Delta State at 4.00 pm daily for the exercise practice. The training session for each day took place between the hours of 4.00 pm and 8.00 pm daily (FMC/ASB/A81.VOL.XII/101). The subjects performed a 24 consecutive day's isometric handgrip exercise at 30% Maximum Voluntary Contraction (MVC). At the end of the 24 days, group one (GP1) discontinued with the exercise protocol, while group two (GP2) and group three (GP3) continued with the exercise protocol for another 24 consecutive days nevertheless GP3 performed at an increased intensity of 50% MVC. The clinical trial was registered with Nigeria Clinical Trial Registry, Federal Ministry of Health, Abuja Nigeriawith Trial No: 1216582 (https://www.nctr.nhrec.net/viewTrials.php?TID=1216582).

RESULTS

At the end of the study, the result shows thatthe number of CD4 cells and CD4/CD8 ratio significantly (P<0.05) increased while the CD8 cell decreased in GP2 and GP3. It was further shown that increase in duration produced a more significant change compared to an increase in intensity of the isometric effort.

CONCLUSION

The study established that isometric handgrip exercise alters the circulating levels of the immune system parameters which could have positive beneficial effects on the prehypertensive individuals as the number of CD4 cells and CD4/CD8 ratio increased especially when practiced over a longer duration.