Effects of different types of exercise on hypertension in middle-aged and older adults: a network meta-analysis.

Objective: This study mainly used network meta-analysis to explore the effect of different types of exercise on hypertension in middle-aged and older adults. Methods: Several databases (e.g., PubMed, Embase, and the Cochrane Library) were used to search for randomized controlled trials on the effects of different types of exercise on hypertension in middle-aged and older adults. Results: A total of 19 articles and 2,385 participants were included in the analysis. Aerobic exercise interventions [MD = -9.254, P < 0.05, 95% CI (-14.810, -3.698)] and static exercise interventions [MD = -10.465, P < 0.05, 95% CI (-18.135, -2.794)] had a significant effect on the improvement in systolic blood pressure (SBP). For diastolic blood pressure (DBP), aerobic exercise interventions [MD = -1.4096; P > 0.05, 95% CI (-8.2395, 5.4201)] and static exercise interventions [MD = -4.5206, P > 0.05, 95% CI (-14.0436, 5.0023)] were not statistically significant. The results of the surface under the cumulative ranking curve (SUCRA) showed that static exercise improved hypertension better than aerobic exercise. Conclusion: Aerobic exercise and static exercise have been shown to have a good effect on the improvement of hypertension, but the effect on DBP is not significant.

Effect of isometric handgrip exercise on cognitive function: Current evidence, methodology, and safety considerations.

Cognitive function is essential for most behaviors of daily living and is a critical component in assessing the quality of life. Mounting prospective evidence supports the use of isometric handgrip exercise (IHE) as a small muscle mass practice to promote health-related outcomes in clinical and healthy populations. The aim of the present review was to systematically investigate whether IHE is effective in improving the cognitive function of adults (aged ≥18 years). Studies were identified by searching five databases (CINAHL, MEDLINE, SPORTDiscus, PsychINFO, and Web of Science). Eight out of 767 studies met the inclusion criteria, including three types of studies: 1) acute effect for IHE with various intensity protocols (n = 4); 2) acute effect for IHE with one set exhaustion protocol (n = 2); and 3) chronic effect of IHE on cognitive function (n = 2). To assess the methodological quality of studies, the PEDro scale was used (mean score = 6.75). The evidence on whether IHE exerts acute positive effects on cognitive performance is currently rather inconclusive. However, a trend was discernible that implementing IHE can generate a beneficial chronic effect on cognitive function, although the results should be interpreted with caution. The clinical relevance of IHE as a time-efficient type of physical exercise to improve cognitive function warrants further investigation. Methodology and safety considerations were discussed. Systematic Review Registration: (https://osf.io/gbzp9).

Sympathetic Nerve Activity and Blood Pressure Response to Exercise in Peripheral Artery Disease: From Molecular Mechanisms, Human Studies, to Intervention Strategy Development.

Sympathetic nerve activity (SNA) regulates the contraction of vascular smooth muscle and leads to a change in arterial blood pressure (BP). It was observed that SNA, vascular contractility, and BP are heightened in patients with peripheral artery disease (PAD) during exercise. The exercise pressor reflex (EPR), a neural mechanism responsible for BP response to activation of muscle afferent nerve, is a determinant of the exaggerated exercise-induced BP rise in PAD. Based on recent results obtained from a series of studies in PAD patients and a rat model of PAD, this review will shed light on SNA-driven BP response and the underlying mechanisms by which receptors and molecular mediators in muscle afferent nerves mediate the abnormalities in autonomic activities of PAD. Intervention strategies, particularly non-pharmacological strategies, improving the deleterious exercise-induced SNA and BP in PAD, and enhancing tolerance and performance during exercise will also be discussed.

The impact of isometric handgrip exercise and training on health-related factors: A review.

Isometric handgrip exercise has been suggested to promote some health-related factors (e.g., lowering blood pressure). However, there is a need to evaluate whether this type of exercise can be included as an option to elicit these health-related outcomes. The purpose of the article was to systematically review the acute and chronic effects of isometric handgrip exercise on resting blood pressure, pain sensation, cognitive function and blood lipids and lipoproteins. A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 89 studies met our inclusion criteria. Most randomized controlled trials (17/26) reported reductions in resting blood pressure (mostly systolic blood pressure) following isometric handgrip training. There were inconsistent results in isometric handgrip exercise-induced hypotension (i.e., acute response). There was convincing evidence observed in randomized controlled trials (4/6) for isometric handgrip exercise-induced hypoalgesia. Some randomized controlled trials (2/2) supported an improvement in memory performance, but not interference control (0/2), after a session of isometric handgrip exercise. None of the included studies found any effects of isometric handgrip training on blood lipids and lipoproteins. Isometric handgrip exercise appears to be an effective method to improve certain health-related factors. The acute reductions in pain and blood pressure may share a similar central mechanism. However, training-induced reductions in resting blood pressure may be driven by changes in the periphery. Additional work is needed to better understand if (and to what extent) isometric handgrip exercise (or training) influences cognitive function and blood lipids and lipoproteins.

Effect of intermittent isometric handgrip exercise protocol with short exercise duration on cognitive performance.

The handgrip exercise, a small muscle exercise, is useful for exercise therapy, particularly in the elderly and bedridden patients. The isometric handgrip (IHG) exercise has been utilized in training programs to reduce resting blood pressure; however, the acute effects of the IHG exercise on cognitive performance are not fully understood. The present study aimed to investigate the effect of an intermittent IHG exercise protocol with short exercise duration, which minimizes the arterial blood pressure response to exercise, on cognitive performance. Twenty-two young healthy subjects performed the intermittent IHG exercise protocol, which consisted of 30-s IHG and 45-s recovery × 16 trials; the exercise intensity of the IHG exercise was 30% of the maximal voluntary contraction. Cognitive performance was evaluated before and after the exercise with the Go/No-Go and memory recognition tasks. Specifically, the reaction time (RT) and performance accuracy were measured. The intermittent IHG exercise protocol did not change the RT or performance accuracy of either the Go/No-Go task (P = 0.222 and P = 0.260, respectively) or the memory recognition task (P = 0.427 and P = 0.245, respectively). These findings suggest that the intermittent IHG exercise protocol with short exercise duration may not provide enough stimulation to improve cognitive performance despite being useful as a safe exercise therapy in the elderly and in patients with cardiovascular disease.

Effects of acute interval handgrip exercise on cognitive performance.

Previous studies have reported that even a single bout of dynamic exercise improves cognitive performance. However, the acute effect of the interval handgrip (HG) exercise protocol, which is effective in reducing resting blood pressure, on cognitive performance is poorly understood. Cognitive performance was assessed in 17 young healthy subjects before and after a resting control (e.g., time control) and the interval HG exercise (Exercise), which consisted of four trials of 2-min HG exercise at 25% of maximum voluntary contraction with 3-min recovery in between each trial. Mean arterial blood pressure (MAP) and middle cerebral artery blood velocity (MCA V) were measured continuously throughout the experiment. Memory recognition and executive function were assessed using memory recognition and Go/No-Go tasks, respectively. During interval HG exercise, MAP and mean MCA V increased from the resting baseline condition (both P < 0.049) and returned to the resting baseline levels during recovery after the interval HG exercise (both P = 1.000). The reaction time and performance accuracy of the memory recognition task did not change in either the time control condition or Exercise condition (P = 0.514 and P = 0.414 respectively). However, the changes in reaction time of Go/No-Go task from the baseline in Exercise condition was significantly shorter than that in time-control condition (P = 0.004) without affecting performance accuracy (P = 0.482). The results of the present study show that an acute interval HG exercise could improve the processing speed in executive function despite no post-exercise improvement in hemodynamic parameters in young healthy subjects. These findings suggest that the interval HG exercise is a useful exercise mode that can be expected to have a positive effect on the processing speed in executive function regardless of cardiovascular adaptation to exercise.

Isometric Exercise Training: A Review of Hypothesized Mechanisms and Protocol Application in Persons with Hypertension.

According to the American Heart Association 116.4 million, or 46% of US adults are estimated to have hypertension. Although, traditional moderate intensity aerobic exercise training is associated with reducing blood pressure by 5-8 mmHg, barriers to this modality of exercise training exist. Thus, the purpose of this review is to evaluate the mechanisms and incorporation of isometric exercise training (IET) as an adjunctive mode of exercise in a population with HTN. Based upon the articles reviewed from the years 2000-2020 which incorporated IET and provided clear protocols lasting 4 or more weeks, meaningful reductions in blood pressure occurred following IET (SBP, -9.7 ± 3.3 mmHg; DBP, -4.8 ± 2.6 mmHg) which support the need to increase adoption of this exercise form into practice to help treat hypertension. Specifically, an IET program of 12-20 minutes per day, 3 times per week, could improve blood pressure reduction in those with hypertension. IET has the potential to produce significant and clinically meaningful blood pressure reductions and could serve as an adjunctive exercise modality alongside the established exercise prescription for those with hypertension.

Exercise and Coronary Heart Disease.

Coronary artery disease (CAD) can be obstructive or nonobstructive. Patients with nonobstructive and stable angina pectoris are usually women. Nonobstructive CAD is caused by endothelial dysfunction at the microvascular level, such as cardiac syndrome X and coronary slow flow syndrome. Even if coronary anatomy is nonobstructive, the presence of myocardial ischemia is a major determinant for the exercise program. CAD is a chronic inflammatory disease, and the progression of the disease can lead to a rapid change in the functional capacity of CAD patients. Exercise training is a major component of cardiac rehabilitation and reduces cardiovascular mortality, morbidity, and rehospitalization as well as improves psychological stress and controls risk factors of CAD, such as diabetes mellitus, hypertension, and obesity. It is possible that the quality of life of patients with CAD can be improved by using appropriate exercise therapy. However, the exercise programs among CAD patients are highly underutilized. This chapter will summarize the research progress of exercise in the prevention and treatment of CAD as well as how to create safe exercise programs and the importance of exercise for patients with CAD. In addition, exercise training has fundamental beneficial effects on ischemic and nonischemic heart failure.

Effects of isometric resistance training on blood pressure and physical fitness of men

Abstract AIMS The present study aimed to investigate the effects of whole body isometric resistance training (IRT) on blood pressure (BP), strength and aerobic fitness. We also analyzed whether the effects of whole body isometric training compares to whole body dynamic resistance training (DRT). METHODS Twenty-nine pre-hypertensive sedentary males, aged between 40 and 60 years were divided into three groups: IRT (n = 10), DRT (n = 9), and Control (n = 10). Both programs involved whole body resistance training, and occurred for 12 weeks, three times/week, at an intensity of 60% of a dynamic one repetition maximum test (1RM). Before and after 12 weeks, 24 hours blood pressure monitoring, 1RM strength and aerobic fitness were assessed. RESULTS IRT reduced diastolic BP values during a 24-hour period and daytime. There was also a decrease in mean BP values during daytime (P<0.05). No interaction between time and group in systolic BP, diastolic BP, mean BP, heart rate and arterial stiffness index were observed (P>0.05). IRT increased strength and aerobic fitness when compared to Control group. However, these changes were lower than DRT regarding strength (DRT: ∆ = 43.1±10.6% vs. IRT: ∆ = 24.1±7.1% vs. CON: Δ = 4.2±11.5%; P<0.05) and aerobic fitness (DRT: ∆ = 22.9±10.7% vs. IRT: ∆ = 12.9±6.1% vs. CON: Δ = -2.1±7.4%; P<0.01). CONCLUSION Whole body IRT reduced diastolic BP and mean BP, however, the decrease was not different for the DRT group. IRT also increased strength and aerobic fitness, nevertheless, these changes were lower than after DRT.

Comparison of Electrocardiographic Criteria for Identifying Left Ventricular Hypertrophy in Athletes from Different Sports Modalities

OBJECTIVES: In athletes, isolated electrocardiogram high voltage criteria are widely used to evaluate left ventricular hypertrophy, but positive findings are thought to represent normal electrocardiogram alterations. However, which electrocardiogram criterion can best detect left ventricular hypertrophy in athletes of various sport modalities remains unknown. METHODS: Five electrocardiogram criteria used to detect left ventricular hypertrophy were tested in 180 male athletes grouped according to their sport modality: 67% low-static and high-dynamic components and 33% high-static and high-dynamic components of exercise. The following echocardiogram parameters are the gold standard for diagnosing left ventricular hypertrophy: left ventricular mass index ≥134 g.m-2, relative wall thickness ≥0.42 mm, left ventricular diastolic diameter index ≥32 mm.m-2, septum wall thickness ≥13 mm, and posterior wall thickness ≥13 mm. Results for the various criteria were compared using the kappa coefficient. Significance was established at p<0.05. RESULTS: Fifty athletes (28%) presented with left ventricular hypertrophy according to electrocardiogram findings, with the following sensitivities and specificities, respectively: 38-53% and 79-83% (Perugia), 22-40% and 89-91% (Cornell), 24-29% and 90% (Romhilt-Estes), 68-87% and 20-23% (Sokolow-Lyon), and 0% and 99% (Gubner). The Perugia and Cornell criteria had higher negative predictive values for the low-static and high-dynamic subgroup. Kappa coefficients were higher for Romhilt-Estes, Cornell and Perugia criteria than for Sokolow-Lyon and Gubner criteria. CONCLUSION: All five evaluated criteria are inadequate for detecting left ventricular hypertrophy, but the Perugia, Cornell and Romhilt-Estes criteria are useful for excluding its presence. The Perugia and Cornell criteria were more effective at excluding left ventricular hypertrophy in athletes involved in a sport modality with low-static and high-dynamic component predominance.

Dynamic and Static Exercises Differentially Affect Plasma Cytokine Content in Elite Endurance- and Strength-Trained Athletes and Untrained Volunteers.

Extensive exercise increases the plasma content of IL-6, IL-8, IL-15, leukemia inhibitory factor (LIF), and several other cytokines via their augmented transcription in skeletal muscle cells. However, the relative impact of aerobic and resistant training interventions on cytokine production remains poorly defined. In this study, we compared effects of dynamic and static load on cytokine plasma content in elite strength- and endurance-trained athletes vs. healthy untrained volunteers. The plasma cytokine content was measured before, immediately after, and 30 min post-exercise using enzyme-linked immunosorbent assay. Pedaling on a bicycle ergometer increased IL-6 and IL-8 content in the plasma of trained athletes by about 4- and 2-fold, respectively. In contrast to dynamic load, weightlifting had negligible impact on these parameters in strength exercise-trained athletes. Unlike IL-6 and IL-8, dynamic exercise had no impact on IL-15 and LIF, whereas static load increases the content of these cytokines by ~50%. Two-fold increment of IL-8 content seen in athletes subjected to dynamic exercise was absent in untrained individuals, whereas the ~50% increase in IL-15 triggered by static load in the plasma of weightlifting athletes was not registered in the control group. Thus, our results show the distinct impact of static and dynamic exercises on cytokine content in the plasma of trained athletes. They also demonstrate that both types of exercises differentially affect cytokine content in plasma of athletes and untrained persons.

Skeletal muscle metaboreflex in patients with chronic renal failure.

The sympathetic nervous system is affected in patients with chronic renal failure (CRF). This study tested the hypothesis that patients with CRF have an altered skeletal muscle metaboreflex. Twenty patients with CRF and 18 healthy subjects of similar age participated in the study. The muscle metaboreflex was determined based on heart rate (HR), mean arterial pressure, calf blood flow and calf vascular resistance (CVR) in response to handgrip exercise. The control of vascular resistance in the calf muscle mediated by the metaboreflex was estimated by subtracting the area under the curve with circulatory occlusion from that without occlusion. Arterial pressure and HR responses during exercise and recovery were similar in two groups of subjects. In the control group, CVR increased during exercise and remained elevated during circulatory occlusion, whereas no significant change was seen in the patients. Thus, the index of the metaboreflex was 7·82 ± 9·57 in the patients versus16·52 ± 14 units in the controls. The findings demonstrate that patients with CRF have a decreased vascular resistance response in the calf during the handgrip exercise, which suggests that CRF condition attenuates this reflex.

Acute effect of static exercise in patients with aortic regurgitation assessed by cardiovascular magnetic resonance: role of left ventricular remodelling.

OBJECTIVE: In patients with aortic regurgitation (AR), the effect of static exercise (SE) on global ventricular function and AR severity has not been previously studied. METHODS: Resting and SE cardiovascular magnetic resonance (CMR) were prospectively performed in 23 asymptomatic patients with AR. RESULTS: During SE, we observed a decrease in regurgitant volume in both end-diastolic (EDV) and end-systolic (ESV) volume in both ventricles, as well as a slight decrease in LV ejection fraction (EF). Interestingly, responses varied depending on the degree of LV remodelling. Among patients with a greater degree of LV remodelling, we observed a decrease in LVEF (56 ± 4 % at rest vs 48 ± 7 % during SE, p = 0.001) as a result of a lower decrease in LVESV (with respect to LVEDV. Among patients with a lower degree of LV remodelling, LVEF remained unchanged. RVEF remained unchanged in both groups. CONCLUSIONS: In patients with AR, SE provoked a reduction in preload, LV stroke volume, and regurgitant volume. In those patients with higher LV remodelling, we observed a decrease in LVEF, suggesting a lower LV contractile reserve. KEY POINTS: • In patients with aortic regurgitation, static exercise reduced preload volume. • In patients with aortic regurgitation, static exercise reduced stroke volume. • In patients with aortic regurgitation, static exercise reduced regurgitant volume. • In patients with greater remodelling, static exercise unmasked a lower contractile reserve. • Effect of static exercise on aortic regurgitation was assessed by cardiac MR.

Home-based isometric exercise training induced reductions resting blood pressure.

PURPOSE: Isometric exercise training (IET) reduces resting blood pressure (BP). Most previous protocols impose exercise barriers which undermine its effectiveness as a potential physical therapy for altering BP. An inexpensive, home-based programme would promote IET as a valuable tool in the fight against hypertension. The aims of this study were: (a) to investigate whether home-based wall squat training could successfully reduce resting BP and (b) to explore the physiological variables that might mediate a change in resting BP. METHODS: Twenty-eight healthy normotensive males were randomly assigned to a control and a 4 week home-based IET intervention using a crossover design with a 4 week 'washout' period in-between. Wall squat training was completed 3 × weekly over 4 weeks with 48 h between sessions. Each session comprised 4 × 2 min bouts of wall squat exercise performed at a participant-specific knee joint angle relative to a target HR of 95% HRpeak, with 2 min rest between bouts. Resting heart rate, BP, cardiac output, total peripheral resistance, and stroke volume were taken at baseline and post each condition. RESULTS: Resting BP (systolic -4 ± 5, diastolic -3 ± 3 and mean arterial -3 ± 3 mmHg), cardiac output (-0.54 ± 0.66 L min-1) and heart rate (-5 ± 7 beats min-1) were all reduced following IET, with no change in total peripheral resistance or stroke volume compared to the control. CONCLUSION: These findings suggest that the wall squat provides an effective method for reducing resting BP in the home resulting primarily from a reduction in resting heart rate.

Non-thermal modulation of sudomotor function during static exercise and the impact of intensity and muscle-mass recruitment.

Aim: Static muscle activation elicits intensity-dependent, non-thermal sweating that is presumably controlled by feedforward (central command) mechanisms. However, it is currently unknown how the size of the recruited muscle mass interacts with that mechanism. To investigate the possible muscle-size dependency of that non-thermal sweating, the recruitment of two muscle groups of significantly different size was investigated in individuals within whom steady-state thermal sweating had been established and clamped. Methods: Fourteen passively heated subjects (climate chamber and water-perfusion garment) performed 60-s, static handgrip and knee-extension activations at 30% and 50% of maximal voluntary force, plus a handgrip at 40% intensity (143.4 N) and a third knee extension at the same absolute force. Local sweating from four body segments (averaged to represent whole-body sudomotor activity), three deep-body and eight skin temperatures, heart rates and perceptions of physical effort were measured continuously, and analyzed over the final 30 s of exercise. Results: In the presence of thermal clamping and low-level, steady-state sweating, static muscle activation resulted in exercise-intensity dependent changes in the whole-body sudomotor response during these handgrip and knee-extension actions (P < 0.05). However, there was no evidence of a dependency on the size of the recruited muscle mass (P > 0.05), yet both dependencies were apparent for heart rate, and partially evident for the sensations of physical effort. Conclusion: These observations represent the first evidence that exercise-related sudomotor feedforward is not influenced by the size of the activated muscle mass, but is instead primarily dictated by the intensity of the exercise itself.

Caloric restriction diminishes the pressor response to static exercise.

BACKGROUND: Astronauts in space consume fewer calories and return to earth predisposed to orthostatic intolerance. The role that caloric deficit plays in the modulation of autonomic control of the cardiovascular system is unknown. Therefore, the purpose of this study was to determine the effects of 6° head-down bedrest (an analog of spaceflight) with a hypocaloric diet (25 % caloric restriction) (CR) on autonomic neural control during static handgrip (HG) and cold pressor (CP) tests. Nine healthy young men participated in a randomized crossover bedrest (BR) study, consisting of four, two-week interventions (hypocaloric ambulatory, hypocaloric bedrest, normocaloric ambulatory, and normocaloric bedrest), each separated by 5 months. Heart rate (HR), arterial pressure, and muscle sympathetic nerve activity (MSNA) were recorded before, during, and after HG (40 % of maximum voluntary contraction to fatigue), post-exercise muscle ischemia (forearm occlusion), and CP. Bedrest and nutritional combinations were compared using two-way ANOVA with repeated measures. RESULTS: HR, MSNA, and the change in systolic blood pressure during HG were attenuated with caloric restriction, but post-intervention responses for all groups were similar during post-exercise muscle ischemia. CR was associated with a higher diastolic blood pressure during CP; however, HR was directionally opposite (i.e., increase with BR, decrease with CR). CONCLUSIONS: In summary 14-day caloric/fat restriction attenuated MSNA and pressor responses during isometric exercise to fatigue but not to post-exercise muscle ischemia. This indicates that the integrity of the metaboreflex is maintained whereas the influence of the mechanoreflex and/or central command may be reduced.

Purinergic P2X Receptors and Heightened Exercise Pressor Reflex in Peripheral Artery Disease.

Arterial blood pressure (BP) and vasoconstriction regulated by sympathetic nerve activity (SNA) are heightened during exercise in patients with peripheral artery disease (PAD). The exercise pressor reflex is considered as a neural mechanism responsible for the exaggerated autonomic responses to exercise in PAD. A series of studies have employed a rat model of PAD to examine signal pathways at receptor and cellular levels by which the exercise pressor reflex is amplified. This review will summarize results obtained from recent human and animal studies with respect to contribution of muscle afferents to augmented SNA and BP responses in PAD. The role played by adenosine triphosphate (ATP) and ATP sensitive purinergic P2X receptors will be emphasized.

Nerve Growth Factor, Muscle Afferent Receptors and Autonomic Responsiveness with Femoral Artery Occlusion.

The exercise pressor reflex is a neural control mechanism responsible for the cardiovascular responses to exercise. As exercise is initiated, thin fiber muscle afferent nerves are activated by mechanical and metabolic stimuli arising in the contracting muscles. This leads to reflex increases in arterial blood pressure and heart rate primarily through activation of sympathetic nerve activity (SNA). Studies of humans and animals have indicated that the exercise pressor reflex is exaggerated in a number of cardiovascular diseases. For the last several years, a series of studies have employed a rodent model to examine the mechanisms at receptor and cellular levels by which responses of SNA and blood pressure to static exercise are heightened in peripheral artery disease (PAD), one of the most common cardiovascular disorders. Specifically, femoral artery occlusion is used to study intermittent claudication that is observed in human PAD. Our studies have demonstrated that the receptors on thin fiber muscle afferents including transient receptor potential vanilloid type 1 (TRPV1), purinergic P2X3 and acid sensing ion channel subtype 3 (ASIC3) are engaged in augmented autonomic responses this disease. This review will present some of recent results in regard with several receptors in muscle sensory neurons in contribution to augmented autonomic responses in PAD. We will emphasize the role played by nerve growth factor (NGF) in regulating those sensory receptors in the processing of amplified exercise pressor reflex. Also, we will discuss the role played by hypoxia-inducible facor-1α regarding the enhanced autonomic reflex with femoral artery occlusion. The purpose of this review is to focus on a theme namely that PAD accentuates reflexively autonomic responses to exercise and further address regulatory mechanisms leading to abnormal autonomic responsiveness.

Mechanical and metabolic reflex activation of the sympathetic nervous system in younger adults with metabolic syndrome.

AIM: Based on reports of exaggerated blood pressure responses to whole-body exercise in patients with metabolic syndrome (MetSyn), we tested the hypothesis that MetSyn adults would exhibit augmented sympathetic and pressor responses to mechanoreflex and metaboreflex activation when compared with healthy, age-matched control subjects. METHODS: We studied 12 adults with MetSyn (34±3years) and 12 healthy control subjects (34±3years). Heart rate (HR; ECG), blood pressure (BP; finger photoplethysmography), and MSNA (microneurography of the peroneal nerve) were measured during: (1) static handgrip exercise at 15% of maximal voluntary contraction (MVC), and (2) static handgrip exercise at 30% MVC to fatigue, followed by post-exercise ischemia (PEI). Increases in MSNA, HR, and BP were assessed. RESULTS: During static exercise at both 15 and 30% MVC, increases in MSNA, HR, and BP were not different between groups. MSNA remained significantly elevated from baseline during PEI and responses were not different between groups. CONCLUSION: Sympathetic and pressor responses to mechanoreflex and metaboreflex activation are not augmented in younger adults with MetSyn.

Cardiovascular and autonomic responses to physiological stressors before and after six hours of water immersion.

The physiological responses to water immersion (WI) are known; however, the responses to stress following WI are poorly characterized. Ten healthy men were exposed to three physiological stressors before and after a 6-h resting WI (32-33°C): 1) a 2-min cold pressor test, 2) a static handgrip test to fatigue at 40% of maximum strength followed by postexercise muscle ischemia in the exercising forearm, and 3) a 15-min 70° head-up-tilt (HUT) test. Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), cardiac output (Q), limb blood flow (BF), stroke volume (SV), systemic and calf or forearm vascular resistance (SVR and CVR or FVR), baroreflex sensitivity (BRS), and HR variability (HRV) frequency-domain variables [low-frequency (LF), high-frequency (HF), and normalized (n)] were measured. Cold pressor test showed lower HR, SBP, SV, Q, calf BF, LFnHRV, and LF/HFHRV and higher CVR and HFnHRV after than before WI (P < 0.05). Handgrip test showed no effect of WI on maximum strength and endurance and lower HR, SBP, SV, Q, and calf BF and higher SVR and CVR after than before WI (P < 0.05). During postexercise muscle ischemia, HFnHRV increased from baseline after WI only, and LFnHRV was lower after than before WI (P < 0.05). HUT test showed lower SBP, DBP, SV, forearm BF, and BRS and higher HR, FVR, LF/HFHRV, and LFnHRV after than before WI (P < 0.05). The changes suggest differential activation/depression during cold pressor and handgrip (reduced sympathetic/elevated parasympathetic) and HUT (elevated sympathetic/reduced parasympathetic) following 6 h of WI.