The isometric handgrip exercise as a test for unmasking hypertension in the offsprings of hypertensive parents

Adjusting for muscle strength and body size attenuates sex differences in the exercise pressor reflex in young adults

Females typically exhibit lower blood pressure (BP) during exercise than males. However, recent findings indicate that adjusting for maximal strength attenuates sex differences in BP during isometric handgrip (HG) exercise and postexercise ischemia (PEI; metaboreflex isolation). In addition, body size is associated with HG strength but its contribution to sex differences in exercising BP is less appreciated. Therefore, the purpose of this study was to determine whether adjusting for strength and body size would attenuate sex differences in BP during HG and PEI. We obtained beat-to-beat BP in 110 participants (36 females, 74 males) who completed 2 min of isometric HG exercise at 40% of their maximal voluntary contraction followed by 3 min of PEI. In a subset (11 females, 17 males), we collected muscle sympathetic nerve activity (MSNA). Statistical analyses included independent t tests and mixed models (sex × time) with covariate adjustment for 40% HG force, height2, and body surface area. Females exhibited a lower absolute 40% HG force than male participants (Ps < 0.001). Females exhibited lower Δsystolic, Δdiastolic, and Δmean BPs during HG and PEI than males (e.g., PEI, Δsystolic BP, 15 ± 11 vs. 23 ± 14 mmHg; P = 0.004). After covariate adjustment, sex differences in BP responses were attenuated. There were no sex differences in MSNA. In a smaller strength-matched cohort, there was no sex × time interactions for BP responses (e.g., PEI systolic BP, P = 0.539; diastolic BP, P = 0.758). Our data indicate that sex differences in exercising BP responses are attenuated after adjusting for muscle strength and body size.NEW & NOTEWORTHY When compared with young males, females typically exhibit lower blood pressure (BP) during exercise. Adjusting for maximal strength attenuates sex differences in BP during isometric handgrip (HG) exercise and postexercise ischemia (PEI), but the contribution of body size is unknown. Novel findings include adjustments for muscle strength and body size attenuate sex differences in BP reactivity during exercise and PEI, and sex differences in body size contribute to HG strength differences.

The sympathetic muscle metaboreflex is not different in the third trimester in normotensive pregnant women

Isometric handgrip (IHG) is used to assess sympathetic nervous system responses to exercise and may be useful at predicting hypertension in both pregnant and nonpregnant populations. We previously observed altered sympathetic nervous system control of blood pressure in late pregnancy. Therefore, we measured muscle sympathetic nerve activity (MSNA) and blood pressure during muscle metaboreflex activation (IHG) in normotensive pregnant women in the third trimester compared with in healthy nonpregnant women. Further, 19 pregnant (32 ± 3 wk gestation) and 14 nonpregnant women were matched for age, non/prepregnant body mass index (BMI), and parity. MSNA (microneurography), heart rate (ECG), and arterial blood pressure (Finometer) were continuously recorded during 10 min of rest, and then during 2 min of IHG at 30% of maximal voluntary contraction, and 2 min of postexercise circulatory occlusion (PECO). Baseline sympathetic nerve activity (SNA) was elevated in pregnant (41 ± 11 bursts/min) compared with nonpregnant women (27 ± 9 bursts/min; P = 0.005); however, the sympathetic baroreflex gain and neurovascular transduction were not different between groups (P = 0.62 and P = 0.32, respectively). During IHG and PECO, there were no significant differences in the pressor responses (ΔMAP) between groups, (P = 0.25, main effect of group) nor was the sympathetic response different between groups (interaction effect: P = 0.16, 0.25, and 0.27 for burst frequency, burst incidence, and total SNA, respectively). These data suggest that pregnant women who have maintained sympathetic baroreflex and neurovascular transduction also have similar sympathetic and pressor responses during exercise.NEW & NOTEWORTHY We compared sympathetic nervous system activation by muscle metaboreflex between pregnant women in the third trimester and nonpregnant women. We show that the sympathetic nerve activity and associated pressor responses to isometric handgrip and post-exercise circulatory occlusion are not different between third-trimester pregnant and nonpregnant women. These data suggest that unlike other reflexes (e.g., cold pressor test or head-up tilt), metaboreflex control is maintained in pregnant women.

The Cardiovascular Stress Response as Early Life Marker of Cardiovascular Health: Applications in Population-Based Pediatric Studies-A Narrative Review

Stress inducement by physical exercise requires major cardiovascular adaptations in both adults and children to maintain an adequate perfusion of the body. As physical exercise causes a stress situation for the cardiovascular system, cardiovascular exercise stress tests are widely used in clinical practice to reveal subtle cardiovascular pathology in adult and childhood populations with cardiac and cardiovascular diseases. Recently, evidence from small studies suggests that the cardiovascular stress response can also be used within research settings to provide novel insights on subtle differences in cardiovascular health in non-diseased adults and children, as even among healthy populations an abnormal response to physical exercise is associated with an increased risk of cardiovascular diseases. This narrative review is specifically focused on the possibilities of using the cardiovascular stress response to exercise combined with advanced imaging techniques in pediatric population-based studies focused on the early origins of cardiovascular diseases. We discuss the physiology of the cardiovascular stress response to exercise, the type of physical exercise used to induce the cardiovascular stress response in combination with advanced imaging techniques, the obtained measurements with advanced imaging techniques during the cardiovascular exercise stress test and their associations with cardiovascular health outcomes. Finally, we discuss the potential for cardiovascular exercise stress tests to use in pediatric population-based studies focused on the early origins of cardiovascular diseases.

Angiotensin receptor blockade with Losartan attenuates pressor response to handgrip contraction and enhances natriuresis in salt loaded hypertensive subjects: a quasi-experimental study among Nigerian adults

INTRODUCTION

Sympathetic and Renin-Angiotensin-Aldosterone systems play crucial roles in blood pressure response to increased salt intake. This study investigated the effects of angiotensin receptor blocker (ARB) and sympathetic excitation on the responses of blood pressure (BP) and peripheral vascular resistance (PVR) in salt loaded normotensive (NT) and hypertensive (HT) Nigerian subjects.

METHODS

16 NT and 14 HT participants, that were age-matched [39.9 ± 1.3 vs 44.1±2.1yrs (P= 0.10)], underwent 5 days each of oral administration of 200mmol NaCl, and 200mmol NaCl + 50mg Losartan, preceded by a baseline control condition. BP and PVR responses to 30% Maximum Voluntary Contraction (MVC) of handgrip (HG) for one minute were determined at baseline, after salt load and after salt + Losartan. Data were presented as Mean ± SEM, and analyzed with two-way ANOVA and paired t-test, with P<0.05 accepted as significant.

RESULTS

BP and PVR were significantly increased by HG at baseline, after salt load and after salt + Losartan in NT and HT. Salt load augmented the HG-induced SBP (P=0.04) and MABP responses (P=0.02) in HT. While Losartan attenuated the HG- induced Systolic Blood Pressure (SBP) SBP response (P=0.007) and DBP response (P=0.003) in HT and NT respectively after salt + Losartan. HG-induced PVR response was significantly accentuated after salt load in HT (P=0.005), but it was not significant in NT (P=0.38).

CONCLUSION

The implication of our finding is that angiotensin II receptor blockade possibly attenuates salt-induced sympathetic nerve excitation in black hypertensive patients.

Cardiovascular Responses to an Isometric Handgrip Exercise in Females with Prehypertension

BACKGROUND

Hypertensive individuals are known to exhibit greater increases in blood pressure during an isometric handgrip exercise (IHE) than their normotensive counterparts.

AIM

This study tests the hypothesis that, compared to normotensive individuals, prehypertensive individuals exhibit an exaggerated response to IHE.

MATERIALS AND METHODS

In this study, the effects of IHE were compared in matched prehypertensive vs. normotensive healthy African-American females. Six healthy young adult African-American female university students were screened in a physician's office for blood pressure in the range of prehypertension, systolic blood pressure (SBP) 120-139 mmHg and diastolic blood pressure (DBP) 80-89 mmHg. Six young adult African-American women were also recruited to serve as a healthy normotensive control group with SBP ≤119 mmHg and DBP ≤79 mmHg. Cardiovascular fitness was determined by peak oxygen uptake (VO2 peak) measured during a progressive exercise test.

RESULTS

During the handgrip exercise, the prehypertensive group exhibited greater increases in SBP (from 139 ± 6 to 205 ± 11 mmHg, +48%) than the controls (from 132 ± 3 to 145 ± 3 mmHg, +10%); intergroup difference P < 0.001. The prehypertensive group also exhibited greater increases in DBP (from 77 ± 2 to 112 ± 5 mmHg, +46%) compared to the controls (from 72 ± 3 to 78 ± 4 mmHg, +8%); intergroup difference P < 0.001. The increase in systemic vascular resistance was also greater in the prehypertensive group (from 1713 ± 91 to 2807 ± 370 dyne.s.cm(-5), +64%) than in the controls (from 1668 ± 80 to 1812 ± 169 dyne.s.cm(-5), +9%); intergroup difference P < 0.05.

CONCLUSION

These results suggest that blood pressure measurements performed during IHE may be a useful screening tool in evaluating prehypertensive individuals for antihypertensive treatments.

Comparison of two isometric handgrip protocols on sympathetic arousal in women

Isometric handgrip is commonly used in stress research because the task reliably increases sympathetic arousal. Various handgrip protocols have been used; they vary in handgrip strength, duration of grip, and the number of cycles of handgrip and rest. However, most protocols require the calibration of a maximum voluntary contraction (MVC) prior to the handgrip task, which is not always convenient (i.e., in a functional magnetic resonance imaging study). Here, we wanted to test whether two handgrip protocols with different strength, duration and cycle protocols would reliably elicit sympathetic arousal in the absence of calibrating an MVC. Sixty-two healthy naturally cycling women and women on hormonal contraception participated in one of the two isometric handgrip protocols using a hand therapy ball of medium resistance. Women completed one of the following handgrip protocols: 1) 30% of a perceived maximum voluntary contraction for 3 min or 2) 3 cycles of maximum voluntary contraction for 18s with a one minute rest in between. All handgrip blocks were counterbalanced with a control condition. Sympathetic arousal was measured throughout the session via pupil diameter changes and salivary alpha-amylase. Results indicate that in the absence of calibrating an MVC, the handgrip tasks elicited different changes in sympathetic arousal. Pupil dilation responses increased significantly in the handgrip versus control blocks only in participants in the 18-s protocol. Additionally, more participants exhibited a salivary alpha-amylase response to the handgrip block in the 18-s condition compared to the 3-min condition. Thus, these results suggest that neuroimaging and behavioral studies with isometric handgrip should be able to successfully induce sympathetic nervous activity with the 18-s paradigm, regardless of the handgrip device and the ability to calibrate an MVC.

Effect of isometric handgrip exercise training on resting blood pressure in normal healthy adults

INTRODUCTION

The aim of the present study was to study the effect of isometric handgrip (IHG) exercise training on resting blood pressure in normal healthy volunteers.

MATERIALS AND METHODS

Hand grip spring dynamometer was used for IHG exercise training. A total of 30 normal healthy volunteers in the age group of 20-40 y were enrolled for the study. Exercise training protocol consisted of five 3-min bouts of IHG exercise at 30% of maximum voluntary contraction separated by 5 min rest periods. Exercise was performed 3 times/wk for 10 wk. Subject's blood pressure was measured before and after exercise.

RESULT

There was a significant reduction in resting blood pressure following 10 wk of exercise training. Both Systolic and Diastolic blood pressure reduced significantly (p<0.001).

CONCLUSION

IHG exercise training might be a simple, effective, inexpensive and non-pharmacological method in lowering blood pressure.