Sex Differences in Cardiac Baroreflex Sensitivity after Isometric Handgrip Exercise

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.

Effect of exercise modalities on postexercise hypotension in pre- and postmenopausal women: a systematic review and meta-analysis

Hormonal changes associated with menopause increase the risk of hypertension. Postexercise hypotension (PEH) is an important tool in the prevention and management of hypertension; however, menopause may alter this response. The aim of this systematic review and meta-analysis [International Prospective Registered of Systematic Review (PROSPERO): CRD42023297557] was to evaluate the effect of exercise modalities (aerobic, AE; resistance, RE; and combined exercise, CE: AE + RE) on PEH in women, according to their menopausal status (premenopausal or postmenopausal). We searched controlled trials in PubMed, Web of Science, EBSCO, and Science Direct published between 1990 and March 2023. Inclusion criteria were normotensive, pre- and hypertensive, pre- and postmenopausal women who performed an exercise session compared with a control session and reported systolic blood pressure (SBP) and diastolic blood pressure (DBP) for at least 30 min after the sessions. Methodological quality was assessed using the PEDro scale. Standardized mean differences (Hedge's g) and their 95% confidence intervals (CIs) were calculated, and Q-test and Z-test were conducted to assess differences between moderators. Forty-one trials with 718 women (474 menopausal) were included. Overall, we found with moderate evidence that SBP and DBP decreased significantly after exercise session (SBP: g = -0.69, 95% CI -0.87 to -0.51; DBP: g = -0.31, 95% CI -0.47 to -0.14), with no difference between premenopausal and postmenopausal women. Regarding exercise modalities, RE is more effective than AE and CE in lowering blood pressure (BP) in women regardless of menopausal status. In conclusion, women's menopausal status does not influence the magnitude of PEH, and the best modality to reduce BP in women seems to be RE.NEW & NOTEWORTHY This meta-analysis has demonstrated that a single bout of exercise induces postexercise hypotension (PEH) in women and that the hormonal shift occurring with menopause does not influence the magnitude of PEH. However, we have shown with moderate evidence that the effectiveness of exercise modalities differs between pre- and postmenopausal women. Resistance and combined exercises are the best modalities to induce PEH in premenopausal women, whereas resistance and aerobic exercises are more effective in postmenopausal women.

Non-invasive evaluation of autonomic responses in patients with rotator cuff tear-related nocturnal pain

[Purpose] We aimed to determine the autonomic response in patients with rotator cuff tear-related nocturnal pain using nonlinear analysis of heart rate variability. [Participants and Methods] Twenty-eight patients with nocturnal pain who were diagnosed with a rotator cuff tear and received steroid injections, and whose nocturnal pain improved, were divided into a control group (14 patients) and a failure group (14 patients). Pulse wave was measured continuously using BACS Advance equipment (TAOS Co.) for a total of 17 min: 5 min before isometric hand grip, 2 min during isometric hand grip, 5 min after isometric hand grip, and 10 min after isometric hand grip. The autonomic nervous system activity was assessed using detrended fluctuation analysis and approximate entropy. [Results] The α1 values obtained from the detrended fluctuation analysis were significantly higher in the failure group than in the control group at each measurement period. The approximate entropy was normal in 12 (85%) patients in the control group and six (42%) patients in the failure group; it was abnormal in two (15%) patients in the control group and eight (58%) patients in the failure group. [Conclusion] Among patients experiencing nocturnal pain, several have abnormal autonomic response during isometric hand grip.

Post-dynamic, isometric and combined resistance exercise responses in medicated hypertensive men

This study investigated the effects of dynamic resistance exercise (DRE), isometric handgrip exercise (IHE) and combined resistance exercise (DRE+IHE) on post-exercise hypotension (PEH) and its hemodynamic, autonomic, and vascular mechanisms. For that, 70 medicated hypertensives men (52 ± 8 years) were randomly allocated to perform one of the following interventions: DRE (3 sets, 8 exercises, 50% of 1RM), IHE (4 sets, 2 min, 30% of MVC), CRE (DRE+IHE) and control (CON, seated rest). Before and after the interventions, blood pressure (BP), systemic hemodynamics, cardiovascular autonomic modulation and brachial vascular parameters were evaluated. After the DRE and CRE, systolic and mean BP decreased (SBP = -7 ± 6 and -8 ± 8 mmHg; MBP -4 ± 5 and -5 ± 5 mmHg, respectively, all P < 0.05), vascular conductance increased (+ 0.47 ± 0.61 and +0.40 ± 0.47 ml.min-1.mmHg-1, respectively, both P < 0.05) and baroreflex sensitivity decreased (-0.15 ± 0.38 and -0.29 ± 0.47 ms/mmHg, respectively, both P < 0.05) in comparison to pre-exercise values. No variable presented any significant change after IHE. The responses observed after CRE were similar to DRE and significantly different from CON and IHE. In conclusion, DRE, but not IHE, elicits PEH, which happens concomitantly to skeletal muscle vasodilation and decreased baroreflex sensitivity. Moreover, adding IHE to DRE does not potentiate PEH and neither changes its mechanisms.Clinical Trial Registration: Data from this study derived from an ongoing longitudinal clinical trial approved by the Institution's Ethics Committee of Human Research (process 2.870.688) and registered at the Brazilian Clinical Trials (RBR-4fgknb) at http://www.ensaiosclinicos.gov.br .

Sports activities and cardiovascular system change

Sports activity is generally considered to be beneficial to health. The World Health Organization (WHO) recommends physical activity as part of a healthy lifestyle. Sports activities significantly affect the cardiovascular system. A number of studies show that they significantly reduce the risk of cardiovascular disease as well as decrease cardiovascular mortality. This review discusses changes in various cardiovascular parameters in athletes - vagotonia/bradycardia, hypertrophy of heart, ECG changes, blood pressure, and variability of cardiovascular parameters. Because of its relationship to the cardiovascular system, VO2max, which is widely used as an indicator of cardiorespiratory fitness, is also discussed. The review concludes with a discussion of reactive oxygen species (ROS) and oxidative stress, particularly in relation to changes in the cardiovascular system in athletes. The review appropriately summarizes the above issues and points out some new implications.

Spontaneous baroreflex sensitivity is attenuated in male UCD-type 2 diabetes mellitus rats: A link between metabolic and autonomic dysfunction

Patients with type 2 diabetes mellitus (T2DM) have impaired arterial baroreflex function, which may be linked to the co-existence of obesity. However, the role of obesity and its related metabolic impairments on baroreflex dysfunction in T2DM is unknown. This study aimed to investigate the role of visceral fat and adiponectin, the most abundant cytokine produced by adipocytes, on baroreflex dysfunction in T2DM rats. Experiments were performed in adult male UCD-T2DM rats assigned to the following experimental groups (n = 6 in each): prediabetic (Pre), diabetes-onset (T0), 4 weeks after onset (T4), and 12 weeks after onset (T12). Age-matched healthy Sprague-Dawley rats were used as controls. Rats were anesthetized and blood pressure was directly measured on a beat-to-beat basis to assess spontaneous baroreflex sensitivity (BRS) using the sequence technique. Dual-energy X-ray absorptiometry (DEXA) was used to assess body composition. Data are presented as mean ± SD. BRS was significantly lower in T2DM rats compared with controls at T0 (T2D: 3.7 ± 3.2 ms/mmHg vs Healthy: 16.1 ± 8.4 ms/mmHg; P = 0.01), but not at T12 (T2D: 13.4 ± 8.1 ms/mmHg vs Healthy: 9.2 ± 6.0 ms/mmHg; P = 0.16). T2DM rats had higher visceral fat mass, adiponectin, and insulin concentrations compared with control rats (all P < 0.01). Changes in adiponectin and insulin concentrations over the measured time-points mirrored one another and were opposite those of the BRS in T2DM rats. These findings demonstrate that obesity-related metabolic impairments may contribute to an attenuated spontaneous BRS in T2DM, suggesting a link between metabolic and autonomic dysfunction.

Effect of a home-based isometric handgrip training programme on systolic blood pressure in adults: A randomised assessor-blinded trial

OBJECTIVES

To evaluate the effects of 20 weeks of home-based isometric handgrip training (IHT) compared with usual care on systolic blood pressure (SBP) in adults.

DESIGN AND PARTICIPANTS

This was a randomised, controlled, assessor-blinded trial. Participants were randomised to either IHT (intervention group) or usual care (control group).

INTERVENTIONS

Participants randomised to the intervention group performed a session of 16 min of effective workout home-based IHT three times per week for 20 weeks. Participants randomised to the control group were asked to continue their daily activities as usual.

OUTCOMES

The primary outcome was the difference in SBP between groups over 20 weeks. Secondary outcomes were diastolic blood pressure, heart rate, handgrip strength, and self-administered home blood pressure measures.

RESULTS

Forty-eight adults (mean [SD] age, 64 [8] years) were included in this trial. The adjusted between-group mean difference in SBP was 8.12 mmHg (95% CI 0.24 to 16.01, p = 0.04) - favouring the usual care group. No differences between groups were found in any of the home blood pressure measurements.

CONCLUSIONS

This trial showed that 20 weeks of home-based isometric handgrip training was not superior compared to the usual care in lowering SBP.

A single high-fat Western meal modulates vascular responsiveness to sympathetic activation at rest and during exercise in humans: a randomized controlled trial

A single high-fat Western meal transiently reduces endothelium-dependent vasodilation at rest, but the interaction with sympathetic vasoconstrictor activity during exercise remains unknown. Herein, we tested the hypothesis that a single high-fat Western meal would impair the ability of contracting skeletal muscle to offset vascular responsiveness to sympathetic activation during exercise, termed functional sympatholysis. In 18 (10 females/8 males) healthy young adults, forearm blood flow (Doppler ultrasound) and beat-to-beat arterial pressure (photoplethysmography) were measured during lower-body negative pressure (LBNP; -20 mmHg) applied at rest and simultaneously during low (15% maximum contraction) and moderate (30% maximum contraction)-intensity rhythmic handgrip exercise. The magnitude of sympatholysis was calculated as the difference of LBNP-induced changes in forearm vascular conductance (FVC) between handgrip and rest. Experiments were performed preprandial and 1 h, 2 h, and 3 h after a high- or low-fat meal. In the preprandial state, LBNP decreased resting FVC (Δ-54 ± 10%), and these responses were attenuated during low (Δ-17 ± 7%)- and moderate (Δ-8 ± 6%)-intensity handgrip exercise. Following a high-fat meal, LBNP induced attenuated decreases in resting FVC (3 h postprandial, Δ-47 ± 10%, P = 0.002 vs. preprandial) and blunted attenuation of FVC during low (3 h postprandial, Δ-23 ± 8%, P = 0.001 vs. preprandial)- and moderate (3 h postprandial, Δ-16 ± 6%, P < 0.001 vs. preprandial)-intensity handgrip exercise. The high-fat meal attenuated the magnitude of sympatholysis during low (preprandial, 38 ± 7 vs. 3 h postprandial, 23 ± 8%, P < 0.001)- and moderate (preprandial, 46 ± 11 vs. 3 h postprandial, 31 ± 10%, P < 0.001)-intensity handgrip exercise. The low-fat meal had no impact on these responses. In conclusion, a single high-fat Western meal modulates sympathetic vasoconstriction at rest and during low- and moderate-intensity handgrip exercise in young healthy adults.NEW & NOTEWORTHY We observed that a single high-fat Western meal, but not an isocaloric low-fat meal, attenuated the sympathetic vasoconstriction at rest and the ability of the active skeletal muscle to counteract the vascular responsiveness to sympathetic activation (i.e., functional sympatholysis) during low- and moderate-intensity rhythmic handgrip exercise in healthy young adults. Our findings highlight the potential deleterious vascular effect associated with the consumption of a Western diet.

Ischemic Preconditioning Acutely Improves Functional Sympatholysis during Handgrip Exercise in Healthy Males but not Females

PURPOSE

Ischemic preconditioning (IPC), a procedure that involves the cyclic induction of limb ischemia and reperfusion via tourniquet inflation, has been reported to improve exercise capacity and performance, but the underlying mechanisms remain unclear. During exercise, sympathetically mediated vasoconstriction is dampened in active skeletal muscle. This phenomenon, termed functional sympatholysis, plays a critical role in maintaining oxygen delivery to working skeletal muscle and may contribute to determining exercise capacity. Herein, we investigate the effects of IPC on functional sympatholysis in humans.

METHODS

In 20 (10M/10F) healthy young adults, forearm blood flow (Doppler ultrasound) and beat-to-beat arterial pressure (finger photoplethysmography) were measured during lower body negative pressure (LBNP; -20 mm Hg) applied at rest and simultaneously during rhythmic handgrip exercise (30% maximum contraction) before and after local IPC (4 × 5-min 220 mm Hg) or sham (4 × 5-min 20 mm Hg). Forearm vascular conductance (FVC) was calculated as forearm blood flow/mean arterial pressure and the magnitude of sympatholysis as the difference of LBNP-induced changes in FVC between handgrip and rest.

RESULTS

At baseline, LBNP decreased FVC (females [F] = ∆-41% ± 19%; males [M] = ∆-44% ± 10%), and these responses were attenuated during handgrip (F = ∆-8% ± 9%; M = ∆-8% ± 7%). After IPC, LBNP induced similar decreases in resting FVC (F = ∆-37% ± 19%; M = ∆-44% ± 13%). However, during handgrip, this response was further attenuated in males (∆-3% ± 9%, P = 0.02 vs pre) but not females (∆-5% ± 10%, P = 0.13 vs pre), which aligned with an IPC-mediated increase in sympatholysis (M-pre = 36% ± 10% vs post = 40% ± 9%, P = 0.01; F-pre = 32% ± 15% vs post = 32% ± 14%, P = 0.82). Sham IPC had no effect on any variables.

CONCLUSIONS

These findings highlight a sex-specific effect of IPC on functional sympatholysis and provide evidence of a potential mechanism underlying the beneficial effects of IPC on human exercise performance.

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).

Handgrip exercise induces sex-specific mean arterial pressure and oxygenation responses but similar performance fatigability

Women exhibit an attenuated exercise pressor reflex (EPR) when compared to men. The influence of sex-specific mechanisms related to the EPR and performance fatigability remain to be fully elucidated. The purpose was to determine the impact of oxygenation and metabolic efficiency on sex-specific performance fatigability and increases in mean arterial pressure (MAP) resulting from a fatiguing isometric handgrip (IHG). Twenty-four adults volunteered to perform an IHG at 25% at maximal voluntary isometric contractions (MVICs). Pre- and posttest MVICs were conducted to quantify performance fatigability. MAP was collected at 3 timepoints. A near-infrared spectroscopy device was attached to the forearm to derive the following signals: oxy[haem], deoxy[haem], total[haem], and diff[haem]. These values were normalized and examined across time in 5% segments of time-to-task-failure. Metabolic efficiency was defined as the ratio force:deoxy[haem]. During the IHG, there was a decline in oxy[haem] for the men (b = -0.075), whereas the women demonstrated an increase (b = 0.117). For the men, the diff[haem] tracked the mean oxy[haem] response, but there was no change for the women. The men exhibited greater declines in metabolic efficiency, yet there were no sex differences in PF (46.6 ± 9.7% vs. 45.5 ± 14.2%). For relative MAP, the men (24.5 ± 15.1%) exhibited a greater (p = .03) increase than the women (11.0 ± 17.6%). These results indicated the EPR was more prominent for the men, perhaps due to differences in mechanical stimuli and a lack of ability to maintain metabolic efficiency. However, these physiological differences did not induce a sex difference in performance fatigability.

Evaluation of autonomic nervous system responses during isometric handgrip exercise using nonlinear analysis of heart rate variability

[Purpose] The purpose of this study was to examine, using a plethysmogram of the fingertips, autonomic responses at motor intensities of 30% or 50% of maximum voluntary contraction (MVC) during isometric handgrip exercise (IHG). [Participants and Methods] The participants of this study were 15 healthy persons. The finger volume pulse wave of each participant was measured continuously, using a BACS Advance equipment (TAOS Co.), for a total of 17 minutes: 5 minutes before IHG (Pre), 2 minutes during IHG (IHG), the first 5 minutes after IHG (Post 5), and then the second 5 minutes after IHG (Post 10). To evaluate autonomic nervous system activity, we used the Detrended fluctuation analysis (DFA) and Approximate Entropy (ApEn). [Results] During IHG, the pulse rate was significantly higher and the ApEn value was significantly lower than during the other periods of measurement. Compared to other analyzed parameters, ApEn decreased during IHG, but returned to its initial Pre period level during the Post 5 period. The α₁ value derived from the DFA analysis remained at a value of 1 during each measurement time point, indicating the absence of malfunctions in autonomic response. [Conclusion] Isometric handgrip exercise with 30% MVC seemed to be useful for the assessment of autonomic nervous system response.

Postexercise hypotension due to resistance exercise is not mediated by autonomic control: A systematic review and meta-analysis

Changes in autonomic control have been suggested to mediate postexercise hypotension (PEH). We investigated through meta-analysis the after-effects of acute resistance exercise (RE) on blood pressure (BP) and autonomic activity in individuals with normal and elevated BP. Electronic databases were searched for trials including: adults; exclusive RE interventions; and BP and autonomic outcomes measured pre- and postintervention for at least 30 min. Analyses incorporated random-effects assumptions. Thirty trials yielded 62 interventions (N = 480). Subjects were young (33.6 ± 15.6 yr), with systolic BP (SBP)/diastolic BP (DBP) of 124.2 ± 8.9/71.5 ± 6.6 mm Hg. Overall, RE moderately reduced SBP (normal BP: ~1 to 4 mm Hg, p < 0.01; elevated BP: ~1 to 12 mm Hg, p < 0.01) and DBP (normal BP: ~1 to 4 mm Hg, p < 0.03; elevated BP: ~0.5 to 7 mm Hg, p < 0.01), which was in general parallel to sympathetic increase (normal BP: g = 0.49 to 0.51, p < 0.01; elevated BP: g = 0.41 to 0.63, p < 0.01) and parasympathetic decrease (normal BP: g = -0.52 to -0.53, p < 0.01; elevated BP: g = -0.46 to -0.71, p < 0.01). The meta-regression showed inverse associations between the effect sizes of BP vs. sympathetic (SBP: slope - 0.19 to -3.45, p < 0.01; DBP: slope - 0.30 to -1.60, p < 0.01), and direct associations vs. parasympathetic outcomes (SBP: slope 0.17 to 2.59, p < 0.01; DBP: slope 0.21 to 1.38, p < 0.01). In conclusion, changes in BP were concomitant to sympathetic increase and parasympathetic decrease, which questions the role of autonomic fluctuations as potential mechanisms of PEH after RE.

The influence of habitual breaks in sedentary time on cardiovagal baroreflex function

Sedentary time has recently been included in the 24-h activity guidelines. However, the impact of habitual sedentary patterns on autonomic cardiovascular regulation are unclear. We tested the hypothesis that more sedentary time and fewer sedentary breaks were associated with lower cardiovagal baroreflex sensitivity. More frequent sedentary breaks, but not total sedentary time, was independently and positively associated with vagally mediated blood pressure control. Breaking up sedentary time could be more important than total sedentary time for cardiovascular health. Novelty: Breaks in sedentary time is an independent predictor of cardiovagal baroreflex sensitivity, with more frequent breaks associated with better vagally mediated blood pressure regulation.

Sex-Specific Autonomic Responses to Acute Resistance Exercise

Background and Objectives: Acute resistance exercise (RE) reduces vagal modulation and increases sympathovagal balance, which increases the risk for arrythmias. Few studies have examined sex differences in autonomic modulation after acute RE. The purpose of this investigation was to examine sex-specific responses to acute RE on autonomic modulation. Materials and Methods: Twenty-one resistance-trained individuals (men n = 11, women n = 10) between the ages of 19 and 25 y were analyzed for autonomic modulation in response to acute RE and a control (CON). Measures of autonomic modulation were collected at rest, 15 (R15), and 30 (R30) min following both conditions. Heart rate (HR), log transformed root mean square of successive differences (lnRMSSD), total power (lnTP), low-frequency power (lnLF), high-frequency power (lnHF), sample entropy (SampEn), and Lempel-Ziv entropy (LZEn) were measured at all time points. A three-way repeated analysis of variance (ANOVA) was used to analyze sex (men, women) across condition (RE, CON) and time (Rest, R15, R30). Results: The results are similar for all heart rate variability (HRV) variables at rest for both conditions (RE, CON). SampEn was significantly higher in men compared to women at rest for both conditions (p = 0.03), with no differences in LZEn (p > 0.05). There were no significant (p > 0.05) three-way interactions on any variables. Condition by time interactions demonstrated that both sexes increase in HR (p = 0.0001) and lnLF/HF ratio (p = 0.001), but decreases in lnRMSSD (p = 0.0001), lnTP (p < 0.0001), lnLF (p < 0.0001), lnHF (p = 0.0001), and LZEn (p = 0.009) at R15 and R30 compared to rest following acute RE and were different from CON. Condition by time interaction (p = 0.017) demonstrated that SampEn was attenuated at R15 compared to rest, and the CON, but not R30 following acute RE. Conclusion: Although SampEn is more complex at rest in men compared to women, autonomic modulation responses between sexes following acute RE appear to be similar.

Effects of Isometric Biceps Exercise on Blood Pressure in Adults with Hypertension

We investigated the acute effects of isometric biceps exercise on resting and ambulatory blood pressure in hypertensive adults. A total of 12 medicated hypertensive adults (aged 47±7 years; body mass index 27.2±2.7 kg/m²; resting blood pressure 123±12/74±6 mmHg) performed an isometric biceps exercise session (bilateral biceps exercise; 4×1 min at 30% of 1-RM, 2 min recovery) and a control session (without exercise) in a randomized order separated by a 7 to 10-day period. Resting blood pressure, heart rate, and heart rate variability indexes (SDNN, RMSSD, LF, HF, and LF/HF) were measured pre- and up to 30 min post-sessions. Next, ambulatory blood pressure was monitored during 22-hour post-sessions (awake and asleep periods). No significant changes were observed for resting blood pressure, heart rate, or heart rate variability indexes up to 30 min post-sessions (p>0.05). Furthermore, no significant differences were observed in average ambulatory blood pressure values in 22-hour (126±11/71±6 mmHg vs. 126±15/71±9 mmHg), awake (127±10/74±6 mmHg vs. 130±14/75±10 mmHg), and asleep (123±15/68±6 mmHg vs. 120±17/66±9 mmHg) periods between the control and isometric sessions, respectively (p>0.05). In conclusion, an isometric biceps exercise session does not elicit an acute antihypertensive effect in adults with hypertension, which suggests that its prescription to improve the acute BP control is limited.

Effects of isometric handgrip training on blood pressure among hypertensive patients seen within public primary healthcare: a randomized controlled trial

BACKGROUND

Meta-analyses have demonstrated that isometric handgrip training (IHT) decreases blood pressure in hypertensive individuals. Nonetheless, most studies were conducted in laboratory settings and its effects in real-world settings remain unclear.

OBJECTIVE

To analyze the effects of IHT on office and ambulatory blood pressure in hypertensive patients attended within primary healthcare.

DESIGN AND SETTING

Randomized controlled trial conducted in primary healthcare units within the Family Health Program, Petrolina, Pernambuco, Brazil.

METHODS

63 hypertensive patients (30-79 years old; 70% female) were randomly allocated into IHT or control groups. IHT was performed three times per week (4 x 2 minutes at 30% of maximal voluntary contraction, one-minute rest between bouts, alternating the hands). Before and after the 12-week training period, office and ambulatory blood pressure and heart rate variability were obtained. The significance level was set at P < 0.05 (two-tailed testing) for all analyses.

RESULTS

IHT significantly decreased office systolic blood pressure (IHT: 129 ± 4 versus 121 ± 3 mmHg, P < 0.05; control: 126 ± 4 versus 126 ± 3 mmHg, P > 0.05), whereas there was no effect on diastolic blood pressure (IHT: 83 ± 3 versus 79 ± 2 mmHg, P > 0.05; control: 81 ± 3 versus 77 ± 3 mmHg, P > 0.05). Heart rate variability and ambulatory blood pressure were not altered by the interventions (P > 0.05 for all).

CONCLUSION

IHT reduced office systolic blood pressure in hypertensive patients attended within primary care. However, there were effects regarding diastolic blood pressure, ambulatory blood pressure or heart rate variability.

CLINICALTRIALS.GOV IDENTIFIER

NCT03216317.

Sex difference in cerebral blood flow velocity during exercise hyperthermia

INTRODUCTION

Cerebral blood flow and thermal perception during physical exercise under hyperthermia conditions in females are poorly understood. Because sex differences exist for blood pressure control, resting middle cerebral artery velocity (MCA_Vmean), and pain, we tested the hypothesis that females would have greater reductions in MCAv_mean and increased thermal perceptual strain during exercise hyperthermia compared to males.

METHODS

Twenty-two healthy active males and females completed 60 min of matched exercise metabolic heat production in a 1) control cool (24.0 ± 0.0 °C; 14.4 ± 3.4% Rh) and 2) hot (42.3 ± 0.3 °C; 28.4 ± 5.2% Rh) conditions in random order, separated by at least 3 days while MCAv_mean, thermal comfort, and preference was obtained during the exercise.

RESULTS

Compared to 36 °C mean body temperature (M^bt), as hyperthermia increased to 39 °C Mbt, females had a greater reduction in absolute (MCAv_mean), and relative change (%Δ MCAv_mean) and conductance (%Δ MCAv_mean conductance) in MCA_Vmean compared to males (Interaction: Temperature x Sex, P ≤ 0.002). During exercise in cool conditions, absolute and conductance MCAv_mean was maintained from rest through exercise; however, females had greater MCA_Vmean compared to males (Main effect: Sex, P < 0.0008). We also found disparities in females' perceptual thermal comfort and thermal preference. These differences may be associated with a greater reduction in partial pressure of end-tidal CO₂, and different cardiovascular and blood pressure control to exercise under hyperthermia.

CONCLUSIONS

In summary, females exercise cerebral blood flow velocity is reduced to a greater extent (25% vs 15%) and the initial reduction occurs at lower hyperthermia mean body temperatures (~38 °C vs ~39 °C) and are under greater thermal perceptual strain compared to males.

Assessment of baroreceptor reflex sensitivity in young obese Saudi males at rest and in response to physiological challenges

Autonomic imbalance in overweight/obese persons could lead to an increased risk of cardiovascular complications including hypertension and arrhythmias. Baroreceptor reflex sensitivity is a sensitive indicator to detect an altered sympathovagal balance in overweight/obese individuals. This study investigated the effects of overweight/obesity on baroreceptor sensitivity in young Saudi males at rest and in response to physiological challenges.

SUBJECTS AND METHODS

In this cross-sectional study, spontaneous baroreceptor sensitivity at rest and in response to deep breathing, isometric hand grip exercise and moderate intensity isotonic exercise were recorded in 20 normal weight and 20 overweight/obese subjects. Finger arterial blood pressure signal, recorded through Finometer, was used to calculate baroreceptor sensitivity through cross-correlation method. The baroreceptor sensitivity data were log transformed before application of parametric tests.

RESULTS

The spontaneous baroreceptor sensitivity was similar in both groups at baseline, but exhibited a significant increase during deep breathing only in normal weight (p < .001). Immediately after the isotonic exercise the baroreceptor sensitivity was significantly lower than baseline in both normal weight and overweight/obese and remained significantly lower in overweight/obese individuals compared to normal weight (p < .05) throughout the recovery period. There was a significant rise in baroreceptor sensitivity after isometric exercise in overweight/obese group only (p = .001). Pearson's correlation showed a significant negative correlation of baroreceptor sensitivity with body mass index during deep breathing (r = -.472, p = .004) and in post-isotonic exercise recovery period (r = -.414, p = .013).

CONCLUSION

A significantly reduced baroreceptor sensitivity response to deep breathing, reduced baroreceptor sensitivity recovery after isotonic exercise, and an exaggerated shoot up after isometric exercise in overweight/obese suggests an altered sympathovagal balance. Baroreceptor sensitivity measurements in response to physiological challenges, deep breathing, and isotonic exercise, may be more sensitive investigations for detection of early attenuation of cardiac autonomic function. This would enable timely intervention thereby delaying complications and improving the quality of life.

Continuous cardiac autonomic and haemodynamic responses to isometric exercise in females

PURPOSE

Hypertension is associated with impaired haemodynamic control mechanisms and autonomic dysfunction. Isometric exercise (IE) interventions have been shown to improve autonomic modulation and reduce blood pressure (BP) predominantly in male participants. The physiological responses to IE are unexplored in female populations; therefore, this study investigated the continous cardiac autonomic and haemodynamic response to a single bout of IE in a large female population.

METHODS

Forty physically inactive females performed a single, individually prescribed isometric wall squat training session. Total power spectral density of heart rate variability (HRV) and associated low-frequency (LF) and high-frequency (HF) power spectral components were recorded in absolute (ms²) and normalised units (nu) pre, during and post an IE session. Heart rate (HR) was recorded via electrocardiography and baroreceptor reflex sensitivity (BRS) via the sequence method. Continuous blood pressure was recorded via the vascular unloading technique and stroke volume via impedance cardiography. Total peripheral resistance (TPR) was calculated according to Ohm's law.

RESULTS

During IE, there were significant reductions in HRV (p < 0.001) and BRS (p < 0.001), and significant increases in heart rate (p < 0.001), systolic, mean and diastolic BP (p < 0.001 for all). In recovery following the IE session, cardiac autonomic parameters returned to baseline (p = 0.974); however, total peripheral vascular resistance significantly reduced below baseline (p < 0.001). This peripheral vascular response was associated with significant reductions in systolic (-17.3 ± 16.5 mmHg, p < 0.001), mean (-18.8 ± 17.4 mmHg, p < 0.001) and diastolic BP (-17.3 ± 16.2 mmHg, p < 0.001), below baseline.

CONCLUSION

A single IE session is associated with improved haemodynamic cardiovascular responses in females. Cardiac autonomic responses return to baseline values, which suggests that alternative mechanisms are responsible for the post-exercise haemodynamic improvements in females. Future mechanistic research is required to investigate the acute and chronic effects of IE in female populations with different resting BP profiles.

Post-Exercise Hypotension and Reduced Cardiac Baroreflex after Half-Marathon Run: In Men, but Not in Women

We examined whether trained women exhibit similar cardiovascular and cardiac baroreflex alterations after a half-marathon compared to men. Thirteen women (39.1 ± 9.3 years; 165 ± 6 cm; 58.2 ± 7.5 kg; maximal aerobic speed (MAS): 13.7 ± 2.2 km·h^-1) and 12 men (45.7 ± 10.5 years; 178 ± 7 cm; 75.0 ± 8.3 kg; MAS: 15.8 ± 2.2 km·h^-1) ran an official half-marathon. Before and 60-min after, cardiovascular variables, parasympathetic (heart rate variability analysis) modulation and cardiac baroreflex function (transfer function and sequence analyses) were assessed during supine rest and a squat-stand test. Running performance was slower in women than in men (120 ± 19 vs. 104 ± 14 min for women and men, respectively). However, when expressed as a percentage of MAS, it was similar (78.1 ± 4.6% and 78.2 ± 5.4% of MAS for women and men, respectively). Before the run, women exhibited lower mean blood pressure (BP), cardiac output (CO) and stroke volume (SV) compared to men, together with higher parasympathetic indexes. After the race, parasympathetic indexes decreased in both sexes, but remained higher in women. Reduced SV, systolic BP and cardiac baroreflex were observed in men but not in women. Contrary to men, a competitive half-marathon did not trigger post-exercise hypotension and a reduced cardiac baroreflex in women.

Sex differences in cardiac vagal reactivation from the end of isometric handgrip exercise and at the onset of muscle metaboreflex isolation

A parasympathetic reactivation is an underlying mechanism mediating the rapid fall in heart rate (HR) at the onset of post-exercise ischemia (PEI) in humans. Herein, we tested the hypothesis that, compared to men, women present a slower HR recovery at the cessation of isometric handgrip exercise (i.e., onset of PEI) due to an attenuated cardiac vagal reactivation. Forty-seven (23 women) young and healthy volunteers were recruited. Subjects performed 90s of isometric handgrip exercise at 40% of maximal voluntary contraction followed by 3-min of PEI. The onset of PEI was analyzed over the first 30s in 10s windows. Cardiac vagal reactivation was indexed using the HR fall and by HR variability metrics (e.g., RMSSD and SDNN) immediately after the cessation of the exercise. HR was significantly increased from rest during exercise in men and women and increases were similar between sexes. However, following the cessation of exercise, the HR recovery was significantly slower in women compared to men regardless of the time point (women vs. men: ∆-14 ± 8 vs. ∆-18 ± 6 beats.min^-1 at 10s; ∆-20 ± 9 vs. ∆-25 ± 8 beats.min^-1 at 20s; ∆-22 ± 10 vs. ∆-27 ± 9 beats.min^-1 at 30s; P = .027). RMSSD and SDNN increased at the cessation of exercise in greater magnitude in men compared to women. These findings demonstrate that women had a slower HR recovery at the cessation of isometric handgrip exercise and onset of PEI compared to men, suggesting a sex-related difference in cardiac vagal reactivation in healthy young humans.

Is pelvic floor muscle training able to alter the response of cardiovascular autonomic modulation and provide a possible cardiovascular benefit to pregnant women?

AIMS

To evaluate the acute and chronic effect of an exercise protocol of pelvic floor muscles (PFMs) contraction on the heart period (HP) and systolic arterial pressure (SAP) variabilities and baroreflex sensitivity (BRS) at rest in pregnant women; and to evaluate if this progressive exercise protocol was well-tolerated by the pregnant women studied.

METHODS

We evaluated 48 women at 18 weeks of pregnancy by vaginal palpation, vaginal manometry, and cardiopulmonary exercise test. They were divided in control (CG; 31.75 ± 3.91 years) and training groups (TG; 30.71 ± 3.94 years). At 19 and 36 weeks of pregnancy, electrocardiogram and noninvasive peripheral SAP data were collected at rest before and after 10 PFM contractions. TG performed PFMT from the 20th to the 36th week. HP and SAP variabilities were analyzed by spectral and symbolic analysis. The baroreflex was evaluated by cross-spectral analysis between the HP and SAP series.

RESULTS

The groups did not differ in relation to VO₂ , HP and SAP variabilities, and BRS at the beginning of the protocol. TG increased the endurance of the PFM after training. PFM contraction did not change the HP and SAP variabilities, and BRS at the 18th week. After the training, the TG presented lower SAP mean, lower BF of SAP variability, and higher BRS than CG.

CONCLUSIONS

Acute PFM contractions did not alter HP and SAP variabilities and BRS, but PFMT resulted in a lower SAP mean and higher BRS in trained pregnant when compared to the untrained.

Characterization of resting and exercise inter-arm differences in SBP to isometric handgrip exercise in males and females

A large inter-arm difference (IAD; ≥10 mmHg) in SBP is linked to cardiovascular and peripheral vascular disease, hypertension, and premature mortality. Exercise-induced IAD (eIAD) is related to resting IAD, and acute aerobic activity alters eIAD and reduces IAD in recovery. Isometric handgrip exercise (IHE) affects blood pressure (BP), though the eIAD response to IHE is unknown. Further, the eIAD response may differ between males and females.

OBJECTIVES

To characterize the eIAD response to IHE in males and females.

METHODS

On visit 1, participants (16 females and 15 males, aged 18-35 years) completed three maximal voluntary isometric contractions (MVIC) per arm. On visit 2, before IHE, a series of three simultaneous, bilateral BP measures were averaged at rest. During IHE, participants maintained handgrip at 20% of MVIC for 2 minutes (arm randomly assigned), at which time bilateral BP was measured (IHE) during exercise and subsequent recovery (REC1 and REC2). Repeated-measures analysis of variance assessed eIAD and SBP (time × sex).

RESULTS

IHE increased absolute eIAD (4 mmHg). Differences in relative eIAD were observed at IHE and REC2 based on resting IAD status (P < 0.05). Females only had an exaggerated SBP and pulse pressure response in the working arm.

CONCLUSION

Acute IHE was shown to augment eIAD. Further eIAD and resting IAD were related. Acute IHE induced different bilateral responses between males and females, though the impact of sex on eIAD warrants further investigation. Future studies should address the effects of repeated bouts of IHE, which may benefit individuals with a large resting IAD.

Gender Differences in Hemodynamic Regulation and Cardiovascular Adaptations to Dynamic Exercise

Exercise is a major challenge for cardiovascular apparatus since it recruits chronotropic, inotropic, pre-load, and afterload reserves. Regular physical training induces several physiological adaptations leading to an increase in both cardiac volume and mass. It appears that several gender-related physiological and morphological differences exist in the cardiovascular adjustments and adaptations to dynamic exercise in humans. In this respect, gender may be important in determining these adjustments and adaptations to dynamic exercise due to genetic, endocrine, and body composition differences between sexes. Females seem to have a reduced vasoconstriction and a lower vascular resistance in comparison to males, especially after exercise. Significant differences exist also in the cardiovascular adaptations to physical training, with trained women showing smaller cardiac volume and wall thickness compared with male athletes. In this review, we summarize these differences.

Effects of Isometric Handgrip Training in Patients With Peripheral Artery Disease: A Randomized Controlled Trial

Background Meta-analyses have shown that isometric handgrip training (IHT) can reduce brachial systolic and diastolic blood pressure (BP) by >6/4 mm Hg, respectively. However, whether IHT promotes these effects among patients with peripheral artery disease, who exhibit severe impairment in cardiovascular function, is currently unknown. This study aimed to evaluate the effects of IHT on the cardiovascular function of patients with peripheral artery disease. Methods and Results A randomized controlled trial with peripheral artery disease patients assigned to either the IHT or control group was conducted. The IHT group performed 3 sessions per week, for 8 weeks, of unilateral handgrip exercises, consisting of 4 sets of isometric contractions for 2 minutes at 30% of maximum voluntary contraction and a 4-minute interval between sets. The control group received a compression ball in order to minimize the placebo effects, representing sham training. The primary outcome was brachial BP. The secondary outcomes were central BP, arterial stiffness parameters, cardiac autonomic modulation, and vascular function. The IHT program reduced diastolic BP (75 [10] mm Hg preintervention versus 72 [11] mm Hg postintervention), with no change in the control group (74 [11] mm Hg preintervention versus 74 [11] mm Hg postintervention), with this between-group difference being significant (P=0.04). Flow-mediated dilation improved in the IHT group (6.0% [5.7] preintervention versus 9.7% [5.5] postintervention), with no change in the control group (7.6% [5.5] preintervention versus 7.4% [5.1] postintervention), with this between-group difference being significant (P=0.04). There was no change in other measured variables over the intervention period. Conclusions IHT reduced brachial diastolic BP and improved local vascular function in patients with peripheral artery disease. Clinical Trial Registration URL: https://www.clinicaltrials.gov/. Unique identifier: NCT02742220.

Meeting international aerobic physical activity guidelines is associated with enhanced cardiovagal baroreflex sensitivity in healthy older adults

PURPOSE

Cardiovagal baroreflex sensitivity (cvBRS) reflects the efficiency of modulating heart rate in response to changes in systolic blood pressure. International guidelines recommend that older adults achieve at least 150 min of moderate-vigorous physical activity per week. We tested the hypothesis that older adults who achieve these guidelines will exhibit greater cardiovagal baroreflex sensitivity versus those who do not.

METHODS

A cross-sectional comparison of older adults who did (active, 66 ± 5 years, 251 ± 79 min/week; n = 19) and who did not (inactive, 68 ± 7 years, 89 ± 32 min/week; n = 17) meet the activity guidelines. Beat-by-beat R-R intervals (electrocardiography) and systolic blood pressure (finger photoplethysmography) were recorded. Spontaneous cardiovagal baroreflex sensitivity was assessed using the sequence technique from 10 min of resting supine data. Cardiovagal baroreflex function was also measured during early phase II and phase IV of the Valsalva maneuver. Peak oxygen uptake was determined during maximal cycle ergometry. Moderate-vigorous intensity physical activity and time spent sedentary were assessed over 5 days using the PiezoRx and activPAL, respectively.

RESULTS

Groups had similar peak oxygen uptake (active 25 ± 9 vs. inactive 22 ± 6 ml/kg/min; p = 0.218) and sedentary time (active 529 ± 60 vs. inactive 568 ± 88 min/day; p = 0.130). However, the active group had greater (all, p < 0.019) cvBRS at rest (9.1 ± 2.7 vs. 5.0 ± 1.9 ms/mmHg), during phase II (8.2 ± 3.8 vs. 5.4 ± 2.1 ms/mmHg), and during phase IV (9.9 ± 3.8 vs. 5.6 ± 1.6 ms/mmHg). In the pooled sample, moderate-vigorous physical activity was positively correlated (all, p < 0.015) with spontaneous (R = 0.427), phase II (R = 0.447), and phase IV cvBRS (R = 0.629).

CONCLUSIONS

Independent of aerobic fitness and sedentary time, meeting activity guidelines was associated with superior cardiovagal baroreflex sensitivity at rest and during the Valsalva maneuver in older adults.

Muscle metaboreflex activation via postexercise ischemia as a tool for teaching cardiovascular physiology for undergraduate students

The cardiovascular responses to exercise are mediated by several interactive neural mechanisms, including central command, arterial baroreflex, and skeletal muscle mechano- and metaboreflex. In humans, muscle metaboreflex activation can be isolated via postexercise ischemia (PEI), which increases sympathetic nerve activity and partially maintains the exercise-induced increase in arterial blood pressure. Here, we describe a practical laboratory class using PEI as a simple and useful technique to teach cardiovascular physiology. In an undergraduate exercise physiology class ( n = 47), a traditional 4-h lecture was conducted discussing the neural control mechanisms of cardiovascular regulation during exercise. Thereafter, eight students (4 men and 4 women) were selected to participate as a volunteer of a practical laboratory class. Each participant performed 90 s of isometric handgrip exercise at 40% of maximal voluntary contraction, followed by 3 min of PEI. Arterial blood pressure and heart rate were measured by digital monitors at rest and during isometric handgrip, PEI, and recovery. In addition, blood samples were collected from the tip of the exercising finger for blood lactate analyses. After the laboratory class, a survey was given to determine the perceptions of the students. The findings demonstrate that this laboratory class has proved to be highly popular with students, who self-reported a significant improvement in their understanding of several aspects of cardiovascular regulation during exercise.

Acute Effect of a Single Session of Pilates on Blood Pressure and Cardiac Autonomic Control in Middle-Aged Adults With Hypertension

Rocha, J, Cunha, FA, Cordeiro, R, Monteiro, W, Pescatello, LS, and Farinatti, P. Acute effect of a single session of Pilates on blood pressure and cardiac autonomic control in middle-aged adults with hypertension. J Strength Cond Res 34(1): 114-123, 2020-We investigated the blood pressure (BP) and heart rate variability (HRV) responses to a single session of Pilates among adults with hypertension. Thirteen participants (7 women), aged 44-66 years, underwent Pilates and nonexercise control sessions separated by 48-72 hours in a randomized counterbalanced order. Blood pressure and HRV indices were simultaneously assessed 10 minutes before and 60 minutes after all sessions in the supine position: root mean square of successive differences (rMSSD), percentage of successive normal sinus RR intervals >50 ms (pNN50), SD of all normal sinus RR intervals over 24 hours (SDNN), and low-frequency (LF) and high-frequency (HF) bands. After an acute session of Pilates, the mean values for area under the curve for systolic BP (p = 0.004, corresponding to -7.4 ± 8.2 mm Hg) and mean arterial pressure (p = 0.023, corresponding to -5.3 ± 5.4 mm Hg) were significantly lower compared to the control session. No significant difference was detected for diastolic BP (-4.2 ± 4.7 mm Hg, p = 0.106). Concomitant to BP reduction, significant lowering of parasympathetic HRV indices occurred: RR intervals (-64.1 ± 69.9 ms·min, p = 0.043), rMSSD (-8.3 ± 15.4 ms·min, p = 0.013), pNN50 (-3.6 ± 13%·min, p = 0.028), and total power (-3,089.4 ± 5,938 m·min, p = 0.037). No difference was found for sympathetic markers: SDNN (-17.7 ± 34.6 ms·min, p = 0.100), LF (-5.2 ± 21,6 n.u.·min, p = 0.417), and LF:HF ratio (-0.3 ± 5.2 ratio·min, p = 0.422). In conclusion, a single session of Pilates reduced BP by ∼5-8 mm Hg in adults with hypertension during the first 60 minutes of post-exercise recovery. Acute BP reduction was concomitant to lowered cardiac parasympathetic activity. Our findings are promising for the use of Pilates as an alternative exercise modality to lower BP.

Supplements with purported effects on muscle mass and strength

PURPOSE

Several supplements are purported to promote muscle hypertrophy and strength gains in healthy subjects, or to prevent muscle wasting in atrophying situations (e.g., ageing or disuse periods). However, their effectiveness remains unclear.

METHODS

This review summarizes the available evidence on the beneficial impacts of several popular supplements on muscle mass or strength.

RESULTS

Among the supplements tested, nitrate and caffeine returned sufficient evidence supporting their acute beneficial effects on muscle strength, whereas the long-term consumption of creatine, protein and polyunsaturated fatty acids seems to consistently increase or preserve muscle mass and strength (evidence level A). On the other hand, mixed or unclear evidence was found for several popular supplements including branched-chain amino acids, adenosine triphosphate, citrulline, β-Hydroxy-β-methylbutyrate, minerals, most vitamins, phosphatidic acid or arginine (evidence level B), weak or scarce evidence was found for conjugated linoleic acid, glutamine, resveratrol, tribulus terrestris or ursolic acid (evidence level C), and no evidence was found for other supplements such as ornithine or α-ketoglutarate (evidence D). Of note, although most supplements appear to be safe when consumed at typical doses, some adverse events have been reported for some of them (e.g., caffeine, vitamins, α-ketoglutarate, tribulus terrestris, arginine) after large intakes, and there is insufficient evidence to determine the safety of many frequently used supplements (e.g., ornithine, conjugated linoleic acid, ursolic acid).

CONCLUSION

 In summary, despite their popularity, there is little evidence supporting the use of most supplements, and some of them have been even proven ineffective or potentially associated with adverse effects.

Blunted cardiovascular responses to exercise in Parkinson’s disease patients: role of the muscle metaboreflex

Patients with Parkinson’s disease (PD) exhibit attenuated cardiovascular responses to exercise. The underlying mechanisms that are potentially contributing to these impairments are not fully understood. Therefore, we sought to test the hypothesis that patients with PD exhibit blunted cardiovascular responses to isolated muscle metaboreflex activation following exercise. For this, mean blood pressure, cardiac output, and total peripheral resistance were measured using finger photoplethysmography and the Modelflow method in 11 patients with PD [66 ± 2 yr; Hoehn and Yahr score: 2 ± 1 a.u.; time since diagnosis: 7 ± 1 yr; means ± SD) and 9 age-matched controls (66 ± 3 yr). Measurements were obtained at rest, during isometric handgrip exercise performed at 40% maximal voluntary contraction, and during postexercise ischemia. Also, a cold pressor test was assessed to confirm that blunted cardiovascular responses were specific to exercise and not representative of generalized sympathetic responsiveness. Changes in mean blood pressure were attenuated in patients with PD during handgrip (PD: ∆25 ± 2 mmHg vs. controls: ∆31 ± 3 mmHg; P < 0.05), and these group differences remained during postexercise ischemia (∆17 ± 1 mmHg vs. ∆26 ± 1 mmHg, respectively; P < 0.01). Additionally, changes in total peripheral resistance were attenuated during exercise and postexercise ischemia, indicating blunted reflex vasoconstriction in patients with PD. Responses to cold pressor test did not differ between groups, suggesting no group differences in generalized sympathetic responsiveness. Our results support the concept that attenuated cardiovascular responses to exercise observed in patients with PD are, at least in part, explained by an altered skeletal muscle metaboreflex.

NEW & NOTEWORTHY Patients with Parkinson’s disease (PD) presented blunted cardiovascular responses to exercise. We showed that cardiovascular response evoked by the metabolic component of the exercise pressor reflex is blunted in patients with PD. Furthermore, patients with PD presented similar pressor response during the cold pressor test compared with age-matched controls. Altogether, our results support the hypothesis that attenuated cardiovascular responses to exercise observed in patients with PD are mediate by an altered skeletal muscle metaboreflex.

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.

GABAergic contribution to the muscle mechanoreflex-mediated heart rate responses at the onset of exercise in humans

Previous studies have indicated that central GABAergic mechanisms are involved in the heart rate (HR) responses at the onset of exercise. On the basis of previous research that showed similar increases in HR during passive and active cycling, we reasoned that the GABAergic mechanisms involved in the HR responses at the exercise onset are primarily mediated by muscle mechanoreceptor afferents. Therefore, in this study, we sought to determine whether central GABA mechanisms are involved in the muscle mechanoreflex-mediated HR responses at the onset of exercise in humans. Twenty-eight healthy subjects (14 men and 14 women) aged between 18 and 35 yr randomly performed three bouts of 5-s passive and active cycling under placebo and after oral administration of diazepam (10 mg), a benzodiazepine that produces an enhancement in GABA_A activity. Beat-to-beat HR (electrocardiography) and arterial blood pressure (finger photopletysmography) were continuously measured. Electromyography of the vastus lateralis was obtained to confirm no electrical activity during passive trials. HR increased from rest under placebo and further increased after administration of diazepam in both passive (change: 12 ± 1 vs. 17 ± 1 beats/min, P < 0.01) and active (change: 14 ± 1 vs. 18 ± 1 beats/min, P < 0.01) cycling. Arterial blood pressure increased from rest similarly during all conditions ( P > 0.05). Importantly, no sex-related differences were found in any variables during experiments. These findings demonstrate, for the first time, that the GABAergic mechanisms significantly contribute to the muscle mechanoreflex-mediated HR responses at the onset of exercise in humans. NEW & NOTEWORTHY We found that passive and voluntary cycling evokes similar increases in heart rate and that these responses were enhanced after diazepam administration, a benzodiazepine that enhances GABA_A activity. These findings suggest that the GABAergic system may contribute to the muscle mechanoreflex-mediated vagal withdrawal at the onset of exercise in humans.