Effect of histamine-receptor antagonism on leg blood flow during exercise

Caffeine Augments Sustained Hyperemia in Previously Exercised Leg in Male Competitive Long-Distance Runners

Blood flow in exercised skeletal muscle remains elevated postexercise, potentially playing a critical role in recovery and adaptation process. However, effective and easily implementable interventions that augment this response have yet to be identified. In this study, we investigated whether caffeine intake enhances sustained postexercise hyperemia in previously active leg in competitive long-distance runners. Ten competitive male long-distance runners participated in baseline measurements, during which cardiorespiratory responses, including leg blood flow measured by ultrasound Doppler equipment, were assessed in a supine position. Subsequently, they ingested either (a) placebo capsules or (b) capsules containing 6 mg/kg caffeine in a randomized, counterbalanced, double-blind, and crossover manner. They then completed 8-min high-intensity treadmill running at 98% of the average running speed of their estimated 10,000-m best time, followed by postexercise measurements assessing the same cardiorespiratory responses. Postexercise leg blood flow was elevated from baseline, and this response was 17% higher in caffeine relative to placebo condition (between-trial difference in average with [95% CI] = 182 [2.33, 363] ml/min, p = .048, d = 1.03). Caffeine ingestion also increased minute ventilation (2.06 [0.603, 3.53] L/min, p = .011, d = 1.17), whereas it reduced end-tidal CO2 partial pressure (-2.09 [-3.68, -0.504] mmHg, p = .015, d = 1.15) postexercise relative to placebo condition. We show that preexercise 6 mg/kg caffeine intake increases postexercise leg blood flow following high-intensity running in male competitive long-distance runners. Our results stimulate future studies to assess if caffeine-induced elevations in leg blood flow accelerates recovery and/or adaptations.

Post-exercise differential response of central and brachial blood pressure in patients with coronary artery disease: A randomized crossover trial

The post-exercise hypotension response is controversial among patients with coronary artery disease (CAD). Factors behind this disparity may include post-exercise differential effects on central and brachial blood pressure (BP), exercise intensity and inter-individual variability. Thus, we investigate group and individual central and brachial BP responses 5, 15 and 30-min after combined exercise of different intensities in participants with and without CAD. Seventeen participants with stable CAD and eighteen aged-matched controls (52-81 years) completed an acute bout of high and moderate-intensity combined exercise. Brachial and central systolic (cSBP) pressures were assessed via oscillometry and carotid tonometry, respectively. Central pulse wave velocity was also measured. Group mean changes were examined with linear mixed models, and bSBP and cSBP post-exercise individual responsiveness quantified via the region of practical equivalence and highest density interval, a Bayesian decision rule. Regardless of exercise intensity, cSBP was persistently increased during recovery in participants with CAD (difference 30 -baseline (d30-bas) = 10, 95% CI: 4 to 17 mmHg, p = 0.001) but reduced in controls (d30-bas = -13, 95% CI: -19 to -7 mmHg, p = 0.003). bSBP was unchanged in both groups (CAD: d30-bas = 1, 95% CI: -3 to 6 mmHg, p = 0.995, control: d30-bas = -4, 95% CI: -2 to 8 mmHg, p = 0.999). Most participants with CAD exhibited sustained elevations in cSBP (n = 10), while most controls were post-exercise hypertensive responders (n = 11) with changes >|5| mmHg. We found differential post-exercise effects on central and brachial BP independent from combined exercise intensity but not clinical population. Clinical trials.gov registration ID: NCT06617117.

Metabolome Alterations Associated with Three-Month Sitting-Time Reduction Among Sedentary Postmenopausal Latinas with Cardiometabolic Disease Risk

Background: Incidence of cardiometabolic disease among U.S. Hispanics/Latinos is higher than in non-Hispanic Whites. Prolonged sitting duration is prevalent in older adults, and compounded with menopause, greatly increases cardiometabolic risk in postmenopausal women. Metabolomic analyses of interventions to reduce sitting are lacking and mechanistic understanding of health-promoting behavior change in postmenopausal Latinas is needed. Methods: To address this knowledge gap, an exploratory analysis investigated the plasma metabolome impact of a 12-week increased standing intervention among sedentary postmenopausal Latinas with overweight or obesity. From a parent-randomized controlled trial, a subset of Best Responders (n = 43) was selected using parameters of highest mean change in sitting bout duration and total sitting time; baseline variable-Matched Controls (n = 43) were selected using random forest modeling. Targeted LC-MS/MS analysis of archived baseline and 12-week plasma samples was conducted. Metabolite change was determined using a covariate-controlled general linear model and multivariate testing was performed. A false discovery rate correction was applied to all analyses. Results: Best Responders significantly changed time sitting (-110.0 ± 11.0 min; -21%), standing (104.6 ± 10.1 min; 40%), and sitting in bouts >30 min (-102.3 ± 13.9 min; -35%) compared to Matched Controls (7.1 ± 9.8 min, -7.8 ± 9.0 min, and -4.6 ± 12.7 min, respectively; all p < 0.001). Twelve-week metabolite change was significantly different between the two groups for 24 metabolites (FDR < 0.05). These were primarily related to amino acid metabolism, improved blood flow, and ATP production. Enzyme enrichment analysis predicted significant changes regulating glutamate, histidine, phenylalanine, and mitochondrial short-chain fatty acid catabolism. Pathway analysis showed significant intervention effects on glutamate metabolism and phenylalanine, tyrosine, and tryptophan biosynthesis, potentially indicating reduced cardiometabolic disease risk. Conclusions: Replacing nearly two hours of daily sitting time with standing and reduced prolonged sitting bouts significantly improved metabolomic profiles associated with cardiometabolic risk among postmenopausal Latinas.

Effect of Aerobic Exercise with Blood Flow Restriction on Postexercise Hypotension in Young Adults: The Role of Histamine Receptors

We tested hypothesis that aerobic exercise with blood flow restriction (BFR) induced postexercise hypotension (PEH), and the reduction in blood pressure (BP) was due to peripheral vasodilation via the histamine receptors. Ten male subjects participated in this study. The subjects were randomly assigned to walk for 10 min at 6.4 km/h, 0% grade with or without BFR after taking histamine receptor blockade. Following exercise, BP was measured at 10 min interval for 60 min. Heart rate (HR), stroke volume (SV), cardiac output (CO), mean arterial pressure (MAP), and total peripheral resistance (TPR) were evaluated. Our results indicated that MAP was significantly lowered immediately after exercise at 20 min, 30 min, and 40 min before the blockade as opposed to after the blockade. A significant reduction in diastolic BP (DBP) occurred. There were no significant differences in HR, SV, CO, and TPR between before the blockade and after the blockade. MAP was substantially decreased at 20 min, 30 min, and 40 min before the blockade compared to resting (-3.2 ± 2.2, -3.3 ± 2.8, and -2.9 ± 2.5, respectively) while increasing MAP after the blockade. The current study demonstrated that low-intensity aerobic exercise with BFR lowered MAP via histamine receptor-induced peripheral vasodilation. In conclusion, BFR exercise training using short periods and low intensity would be greatly beneficial as a potential treatment to lower BP.

Effect of Localized Vibration Massage on Popliteal Blood Flow

There is a broad scope of literature investigating whole-body vibration (WBV) effects on blood flow (BF). However, it is unclear how therapeutic localized vibrations alter BF. Low-frequency massage guns are advertised to enhance muscle recovery, which may be through BF changes; however, studies using these devices are lacking. Thus, the purpose of this study was to determine if popliteal artery BF increases from localized vibration to the calf. Twenty-six healthy, recreationally active university students (fourteen males, twelve females, mean age 22.3 years) participated. Each subject received eight therapeutic conditions randomized on different days with ultrasound blood flow measurements. The eight conditions combined either control, 30 Hz, 38 Hz, or 47 Hz for a duration of 5 or 10 min. BF measurements of mean blood velocity, arterial diameter, volume flow, and heart rate were measured. Using a cell means mixed model, we found that both control conditions resulted in decreased BF and that both 38 Hz and 47 Hz resulted in significant increases in volume flow and mean blood velocity, which remained elevated longer than the BF induced by 30 Hz. This study demonstrates localized vibrations at 38 Hz and 47 Hz significantly increase BF without affecting the heart rate and may support muscle recovery.

Differences in Cardiac Output and Aerobic Capacity Between Sexes Are Explained by Blood Volume and Oxygen Carrying Capacity

Whether average sex differences in cardiorespiratory fitness can be mainly explained by blood inequalities in the healthy circulatory system remains unresolved. This study evaluated the contribution of blood volume (BV) and oxygen (O₂) carrying capacity to the sex gap in cardiac and aerobic capacities in healthy young individuals. Healthy young women and men (n = 28, age range = 20–43 years) were matched by age and physical activity. Echocardiography, blood pressures, and O₂ uptake were measured during incremental exercise. Left ventricular end-diastolic volume (LVEDV), stroke volume (SV), cardiac output (Q), peak O₂ uptake (VO_2peak), and BV were assessed with precise methods. The test was repeated in men after blood withdrawal and reduction of O₂ carrying capacity, reaching women’s levels. Before blood normalization, exercise cardiac volumes and output (LVEDV, SV, Q) adjusted by body size and VO_2peak (42 ± 9 vs. 50 ± 11 ml⋅min^–1⋅kg^–1, P < 0.05) were lower in women relative to men. Blood normalization abolished sex differences in cardiac volumes and output during exercise (P ≥ 0.100). Likewise, VO_2peak was similar between women and men after blood normalization (42 ± 9 vs. 40 ± 8 ml⋅min^–1⋅kg^–1, P = 0.416). In conclusion, sex differences in cardiac output and aerobic capacity are not present in experimental conditions matching BV and O₂ carrying capacity between healthy young women and men.

When it's time for the sex talk, words matter

In recent years, the traditional, unspoken assumption in published biomedical research studies that the young, healthy (usually white) male is the "default human" has received increasing scrutiny and criticism. The historical underrepresentation of female participants in biomedical research has been increasingly recognized and addressed, including with the current call for papers at the American Journal of Physiology-Heart and Circulatory Physiology. Our goal in the present Perspectives is to discuss the topic of terminology (man/woman vs. male/female) for human research participants when considering sex as a biological variable. This important consideration is consistent with the importance of gender identity and related topics to psychological, emotional, and physical health. Just as pronouns are important, so is appropriate terminology when referring to human research volunteers. Despite some disagreement regarding terminology between our two groups of authors, we provide consensus recommendations. Importantly, we all agree that the most vital aspect of the present discussion is the broader focus on sex as a biological variable and appropriate inclusion of biological sex in in vitro, preclinical, and human research studies.