Effects of chronic dietary nitrate supplementation on the hemodynamic response to dynamic exercise.

While acute treatment with beetroot juice (BRJ) containing nitrate (NO3 (-)) can lower systolic blood pressure (SBP), afterload, and myocardial O2 demand during submaximal exercise, effects of chronic supplementation with BRJ (containing a relatively low dose of NO3 (-), 400 mg) on cardiac output (CO), SBP, total peripheral resistance (TPR), and the work of the heart in response to dynamic exercise are not known. Thus, in 14 healthy males (22 ± 1 yr), we compared effects of 15 days of both BRJ and nitrate-depleted beetroot juice (NDBRJ) supplementation on plasma concentrations of NOx (NO3 (-)/NO2 (-)), SBP, diastolic blood pressure (DBP), mean arterial pressure (MAP), CO, TPR, and rate pressure product (RPP) at rest and during progressive cycling exercise. Endothelial function was also assessed via flow-mediated dilation (FMD). BRJ supplementation increased plasma NOx from 83.8 ± 13.8 to 167.6 ± 13.2 µM. Compared with NDBRJ, BRJ reduced SBP, DBP, MAP, and TPR at rest and during exercise (P < 0.05). In addition, RPP was decreased during exercise, while CO was increased, but only at rest and the 30% workload (P < 0.05). BRJ enhanced FMD-induced increases in brachial artery diameter (pre: 12.3 ± 1.6%; post: 17.8 ± 1.9%). We conclude that 1) chronic supplementation with BRJ lowers blood pressure and vascular resistance at rest and during exercise and attenuates RPP during exercise and 2) these effects may be due, in part, to enhanced endothelium-induced vasodilation in contracting skeletal muscle. Findings suggest that BRJ can act as a dietary nutraceutical capable of enhancing O2 delivery and reducing work of the heart, such that exercise can be performed at a given workload for a longer period of time before the onset of fatigue.

Effects of Ovarian Cycle on Hemodynamic Responses during Dynamic Exercise in Sedentary Women.

This study tested the hypothesis that effects of the menstrual cycle on resting blood pressure carry over to dynamic exercise. Eleven healthy females were studied during the early (EP; low estrogen, low progesterone) and late follicular (LP; high estrogen, low progesterone) menstrual phases. Stroke volume (SV), heart rate (HR), cardiac output (CO), systolic blood pressure (SBP), diastolic blood pressure (DBP), and total vascular conductance (TVC) were assessed at rest and in response to mild and moderate cycling exercise during EP and LP. During EP, compared to LP, baseline SBP (111±1 vs. 103±2 mmHg), DBP (71±2 vs. 65±2 mmHg) and mean arterial pressure (MAP) (84±2 vs. 78±1 mmHg) were higher and TVC (47.0±1.5 vs. 54.9±4.2 ml/min/mmHg) was lower (p<0.05). During exercise, absolute values of SBP (Mild: 142±4 vs. 127±5 mmHg; Moderate: 157±4 vs. 144±5 mmHg) and MAP (Mild: 100±3 vs. 91±3 mmHg; Moderate: 110±3 vs. 101±3 mmHg) were also higher, while TVC was lower (Mild: 90.9±5.1 vs. 105.4±5.2 ml/min/mmHg; Moderate: 105.4±5.3 vs. 123.9±8.1 ml/min/mmHg) during EP (p<0.05). However, exercise-induced increases in SBP, MAP and TVC at both work intensities were similar between the two menstrual phases, even though norepinephrine concentrations were higher during LP. Results indicate that blood pressure during dynamic exercise fluctuates during the menstrual cycle. It is higher during EP than LP and appears to be due to additive effects of simultaneous increases in baseline blood pressure and reductions in baseline TVC.

Skeletal muscle metaboreflex is enhanced in postmenopausal women.

This study determined whether an elevated muscle metaboreflex contributes to the excessive blood pressure response to exercise in postmenopausal women. Thirty healthy female volunteers were studied (15 postmenopausal and 15 premenopausal). Stroke volume, heart rate, cardiac output (CO), systolic blood pressure, diastolic blood pressure, and total vascular conductance (TVC) were continuously assessed throughout the experiment. To activate the muscle metaboreflex, occlusion of the vasculature was induced via inflation of a blood pressure cuff (2 min) on the upper arm following static handgrip exercise. Muscle metaboreflex activation increased mean arterial pressure (MAP) in both groups. However, this pressor response was greater in the postmenopausal women (ΔMAP: 21.4 ± 3 vs. 14.5 ± 2 mmHg) (P < 0.05) even though the corresponding increase in CO was less (ΔCO: 0.0 ± 0.2 vs. 0.3 ± 0.2 l/min) (P < 0.05). TVC decreased in both the groups but was more pronounced in the postmenopausal group (ΔTVC: -10.7 ± 2.6 vs. -17.1 ± 3.6 ml/min/mmHg) (P < 0.05). In conclusion, the exaggerated blood pressure response to exercise in postmenopausal women is mediated, in part, by an overactive metaboreflex that is associated with enhanced peripheral vasoconstriction.

Effects of Grape Seed Extract Supplementation on Endothelial Function and Endurance Performance in Basketball Players.

While dietary polyphenols supplements can improve endothelial function and blood flow to exercise, the effects of chronic supplementation with grape seed extract (GSE) containing a high dose of polyphenols on endurance performance are not known. Accordingly, in 12 elite athletes, we compared the effects of both GSE and placebo (PL) on submaximal VO2, time to exhaustion performance, and endothelial function during progressive cycling exercise for 14 days. Endothelial function was evaluated from the brachial artery via flow-mediated dilation (FMD). Compared to PL, GSE decreased submaximal VO2 at 80% and 120% of VO2peak and increased the time to exhaustion (p < 0.05). GSE also resulted in FMD-induced increase in brachial artery diameter (14.4 ± 5.2% vs. 17.6 ± 4.5%, p = 0.035). We demonstrated that chronic supplementation with GSE improved endurance performance and these effects may partially be due to vasodilation in active skeletal muscle mediated by enhanced endothelial function. Thus, our results suggest that GSE appears to be an ergogenic nutraceutical that can improve exercise performance in elite athletes.

Increase in maximal oxygen uptake following 2-week walk training with blood flow occlusion in athletes.

Walk training with blood flow occlusion (OCC-walk) leads to muscle hypertrophy; however, cardiorespiratory endurance in response to OCC-walk is unknown. Ischemia enhances the adaptation to endurance training such as increased maximal oxygen uptake (VO2(max)) and muscle glycogen content. Thus, we investigated the effects of an OCC-walk on cardiorespiratory endurance, anaerobic power, and muscle strength in elite athletes. College basketball players participated in walk training with (n = 7) and without (n = 5) blood flow occlusion. Five sets of a 3-min walk (4-6 km/h at 5% grade) and a 1-min rest between the walks were performed twice a day, 6 days a week for 2 weeks. Two-way ANOVA with repeated measures (groups x time) was utilized (P < 0.05). Interactions were found in VO2(max) (P = 0.011) and maximal minute ventilation (VE(max); P = 0.019). VO2(max) (11.6%) and VE(max) (10.6%) were increased following the OCC-walk. For the cardiovascular adaptations of the OCC-walk, hemodynamic parameters such as stroke volume (SV) and heart rate (HR) at rest and during OCC-walk were compared between the first and the last OCC-walk sessions. Although no change in hemodynamics was found at rest, during the last OCC-walk session SV was increased in all five sets (21.4%) and HR was decreased in the third (12.3%) and fifth (15.0%) sets. With anaerobic power an interaction was found in anaerobic capacity (P = 0.038) but not in peak power. Anaerobic capacity (2.5%) was increased following the OCC-walk. No interaction was found in muscle strength. In conclusion, the 2-week OCC-walk significantly increases VO2(max) and VE(max) in athletes. The OCC-walk training might be used in the rehabilitation for athletes who intend to maintain or improve endurance.

Augmented Hemodynamic Responses in Obese Young Men during Dynamic Exercise: Role of the Muscle Metaboreflex.

Studies found that cardiovascular responses to exercise are enhanced in individuals with obesity and are associated with a greater cardiac output (CO) response compared to normal weight controls. However, the mechanisms underlying these altered responses during dynamic exercise are not clear. We investigated whether the cardiovascular responses mediated by the muscle metaboreflex (MMR) activation are augmented in obese men during both static and dynamic exercise. Twenty males (10 obese (OG) and 10 non-obese (NOG)) were studied. Changes in CO, mean arterial pressure (MAP), and total vascular conductance (TVC) were compared between the two groups during dynamic handgrip exercise (DHE), post-exercise muscular ischemia (PEMI), and dynamic exercise corresponding to 40%, 60% and 80% workloads. Subjects completed 2 min of DHE at 30% of MVC, followed by 2 min of PEMI. MAP, CO, and TVC responses to DHE and dynamic exercise were significantly higher in OG, whereas there were no differences during PEMI. Increases in CO and MAP during mild to heavy dynamic exercise were seen in both groups, but the changes in these variables were greater in the OG. There were no significant differences in TVC between the two groups. Compared to NOG, the augmented blood pressure response to DHE and dynamic exercise in OG was associated with a greater increase in CO. Thus, the augmented CO and MAP responses were not associated with the activation of the MMR. Consequently, additional factors specific to obesity, such as the mechanoreflex, may have been involved.

Inter-modal comparisons of acute energy expenditure during perceptually based exercise in obese adults.

Previous studies have suggested that if exercise intensity is established by perceived effort, the metabolic demand varies among exercise machines and the treadmill optimizes energy expenditure (EE). However, these studies have been completed utilizing young people with normal body fat percentages. Therefore, the purpose of this study was to assess whether there was a difference in acute EE when obese people used different exercise modes at a self-selected intensity (ratings of perceived exertion 11-12) commonly recommended for overweight individuals. Twelve obese subjects (7 male; 5 female; BMI>29 kg/m(2)), aged 37-71 y completed two familiarization trials on four machines: treadmill (TM), stationary cycle (C), body trec elliptical arm/leg (BT), and airdyne (AD). On separate days, subjects then completed a 15 min trial on each machine at a self-selected intensity corresponding to a target RPE of 11-12 on the Borg 15-point scale. Machine order was randomly assigned, and subjects were blinded to the workload throughout each trial. Workload was self-adjusted during the first 5 min and then remained stable for the rest of the trial. Physiological data were obtained during the last 5 min of each trial. The BT produced the highest rate of EE among exercise machines and C the lowest. These results suggest that perceptually-based exercise prescriptions are not reliable across modes typically found in a fitness center environment, and that weight-bearing arm/leg exercise optimizes EE during self-selected exercise of moderate intensity in obese subjects.

Older Korean adults have lower physical function despite longer exercise times compared to their Japanese counterparts: A Japan-Korea comparative study.

AIM: We aimed to compare the level of physical function (PF) and habitual exercise between older Japanese and Korean adults. METHODS: A comparative study was carried out on 1069 community-dwelling older Japanese and Korean adults (mean age 73.9 ± 5.2 years). The participants were asked to complete a self-reported questionnaire regarding habitual exercise and covariates. PF age, a composite measure of PF, was derived from the 12 items, using principal component analysis. PF age and habitual exercise were compared between the Japanese and Korean adults, using analysis of covariance (ancova) and multivariable logistic regression analysis adjusted for all covariates using propensity scores. RESULTS: ancova showed that PF age in older Japanese adults was significantly younger than in their Korean counterparts. Older Japanese adults exercised significantly less frequently than their Korean counterparts. Furthermore, older Japanese adults practiced significantly less walking, mountain climbing and bicycling, but more calisthenics, resistance training, ball games and dances than their Korean counterparts. CONCLUSIONS: We found that older Korean adults had lower PF (3.7 years older in PF age) than their Japanese counterparts. Although the overall frequency and amount of habitual exercise in older Korean adults were higher than those in their Japanese counterparts, particular types of exercise might have contributed to the higher PF levels among older Japanese adults. Thus, older Korean adults might need to engage more in habitual exercises that are specifically effective in maintaining PF. Geriatr Gerontol Int 2018; 18: 576-583.

Histamine H2 receptor blockade augments blood pressure responses to acute submaximal exercise in males.

Histamine is a potent vasodilator that has been found to increase during exercise. We tested the hypothesis that histamine would attenuate blood pressure (BP), cardiac output (CO), and vascular resistance responses to short-term, submaximal dynamic exercise during H2 receptor blockade. Fourteen healthy men (20-29 years of age) were studied. Systolic (SBP), diastolic (DBP), and mean arterial (MAP) BP and heart rate (HR) were assessed at rest and during the last minute of 10 min of submaximal cycling exercise (60% of peak oxygen consumption) in the absence and presence of histamine H2 receptor blockade (ranitidine, 300 mg). Stroke volume (SV) (impedance cardiography) and plasma norepinephrine (NE) were measured, and CO, rate × pressure product (RPP), and total peripheral resistance (TPR) were calculated. Plasma levels of histamine were also measured. H2 blockade had no effects on any variables at rest. During exercise, SBP (184 ± 3 mm Hg vs. 166 ± 2 mm Hg), MAP (121 ± 2 mm Hg vs. 112 ± 5 mm Hg), and RPP (25.9 ± 0.8 × 10(3) mm Hg·beats/min vs. 23.5 ± 0.8 × 10(3) mm Hg/beats·min) were greater during blocked conditions (P < 0.05), and an interaction was observed for TPR. SV, DBP, HR, and NE levels were unaffected by blockade. Plasma histamine increased from 1.83 ± 0.14 ng/mL at rest to 2.33 ± 0.23 ng/mL during exercise (P < 0.05) and was not affected by H2 blockade (1.56 ± 0.23 ng/mL vs. 1.70 ± 0.24 ng/mL). These findings suggest that, during submaximal exercise, histamine attenuates BP, vascular resistance, and the work of the heart via activation of H2 receptors and that these effects occurred primarily in the vasculature and not in the myocardium.

The role of metaboreceptor on exercise in hyperthermic environment with college basketball players.

The objective of this study is to review physiological differences of college basketball players cardiovascular responses and group IV metaboreceptor interactions appearing post muscular ischemia exercise (PEMI) caused by a static handgrip exercise (SHE). The subjects were placed in a temperature and moisture stabilized indoor environment for 2 h in order to measure blood pressure. For the SHE, maximal voluntary contraction of arms with a relative strength of 50 % of the maximum muscular strength was put into isometric training for 2 min. After completing the exercises, cuffs worn on the arms of the subjects were pressurized up to 200 mmHg by applying PEMI to block the artery and vein. In this way, the cardiovascular responses created by SHE and PEMI were measured. Blood samples of subjects were collected from the vein of each upper arm before SHE and after PEMI to measure the metabolite hormone and catecholamine in the blood. Results from the measurements showed a significant decrease of blood pressure under high temperature environments compared to normal temperature environments. With respect to PEMI, increases in blood pressure under the high temperature environment were significantly lower compared to the normal temperature environment. In conclusion, this study revealed that college basketball players with good physical strength had higher sensitivities of arterial baroreceptor. However, blood pressure was not increased accordingly because the increase of cutaneous vasoconstriction due to stimuli of the metaboreceptor under a high temperature environment could not be compensated by arterial baroreflex due to the increase of total vascular conductance.

Mechanisms Underlying Exaggerated Metaboreflex Activation in Prehypertensive Men.

PURPOSE: Previously, we found that the pressor response to muscle metaboreflex activation is enhanced in prehypertension and associated with peripheral vasoconstriction. However, mechanisms underlying this exaggerated response are not clear. Therefore, we tested the hypothesis that activation of this reflex is augmented owing to increased production of muscle metabolites (i.e., lactate, K, and H). METHODS: Twenty-two men (11 normotensive and 11 prehypertensive) were studied. Changes in cardiac output (Q˙), mean arterial pressure (MAP), and total peripheral resistance (TPR) were compared between the two groups during static exercise (SE) and postexercise muscular ischemia (PEMI). Subjects completed 2 min of SE at 50% of maximal voluntary contraction (MVC) followed by 2 min of PEMI. Venous blood samples for determination of metabolites and hormones (catecholamines, vasopressin, and plasma renin activity) were taken from the exercising and nonexercising arm, respectively. RESULTS: Mean arterial pressure responses to SE (39 ± 3 vs 31 ± 2 mm Hg) and PEMI (24 ± 3 vs 19 ± 3 mm Hg) were significantly higher in the prehypertensive group. Increases in lactate and decreases in pH during PEMI were seen in both groups. However, changes in these variables were greater in the prehypertensive group (lactate, 50.1 ± 6.2 vs 32.8 ± 7.6 mg·dL; pH, -0.06 ± 0.02 vs -0.01 ± 0.01) (P < 0.05). Postexercise muscular ischemia did not evoke increases in hormones in either group. CONCLUSIONS: Compared to the normotensive group, the augmented pressor response to the metaboreflex in the prehypertensive group was associated with greater production of muscle metabolites that activate its afferent arm. The augmented response was not associated with activation of the vasopressin and renin-angiotensin systems and greater activation of the sympathetic nervous system was not apparent. Consequently, additional factors specific to prehypertension, such as arterial stiffness, may have been involved.

(-)-Hydroxycitric acid ingestion increases fat utilization during exercise in untrained women.

(-)-Hydroxycitric acid (HCA) is a competitive inhibitor of the enzyme ATPcitrate-lyase, which inhibits lipogenesis in the body. Moreover, HCA increases endurance exercise performance in trained mice and athletes. However, had not been investigated in untrained animals and humans. Therefore, we investigated the effects of short-term HCA ingestion on endurance exercise performance and fat metabolism in untrained women. In two experiments designed as a double-blind crossover test, six subjects ingested 250 mg of HCA or placebo (same amount of dextrin) via capsule for 5 d and then participated in cycle ergometer exercise. They cycled at 40% VO2max for 1 h and then the exercise intensity was increased to 60% VO2max until exhaustion on day 5 of each experiment. HCA tended to decrease the respiratory exchange ratio (RER) and carbohydrate oxidation during 1 h of exercise. In addition, exercise time to exhaustion was significantly enhanced (p<0.05). These results suggest that HCA increases fat metabolism, which may be associated with a decrease in glycogen utilization during the same intensity exercise and enhanced exercise performance.

Augmentation of the exercise pressor reflex in prehypertension: roles of the muscle metaboreflex and mechanoreflex.

This study investigated the hemodynamic mechanisms underlying the exaggerated blood pressure response to muscle contraction in prehypertensive humans and the potential role of skeletal muscle metabo- and mechanoreceptors in this response. To accomplish this, changes in peak mean arterial blood pressure (ΔMAP), cardiac output, and total peripheral resistance (ΔTPR) were compared between prehypertensive (n = 23) and normotensive (n = 19) male subjects during 2 min of static contraction (at 50% of maximal tension), 2 min of postexercise muscle ischemia (metaboreflex), and 1 min of passive dorsiflexion of the foot (tendon stretch, mechanoreceptor reflex). These variables were assessed before and during the interventions. Percentage increases from baseline in MAP and TPR in response to the exercise pressor reflex were augmented in the prehypertensives, compared with the normotensives (44% ± 5% vs. 33% ± 4% and 34% ± 15% vs. 2% ± 8%, respectively) (p < 0.05). Metaboreflex-induced increases in MAP and TPR were also augmented in the prehypertensives (28% ± 5% vs. 14% ± 4% and 36% ± 12% vs. 14% ± 9%, respectively) (p < 0.05). In response to the mechanoreflex, no differences in the percentage increase in MAP or TPR were seen between groups. The results indicate that the reflex pressor response to static contraction is augmented in prehypertension and suggest that this phenomenon is due, at least in part, to enhanced activation of metaboreceptors.

Dance-based aerobic exercise may improve indices of falling risk in older women.

OBJECTIVE: to determine the effect of dance-based aerobic exercise on indices of falling in older women. DESIGN: an exercise intervention trial with participants assigned either to an exercise group or to a control group. SETTING: an exercise hall at a community centre for senior citizens. PARTICIPANTS: thirty-eight healthy women aged 72-87 years, living independently in the community. INTERVENTION: twenty women performed dance-based aerobic exercise for 60 minutes, 3 days a week, for 12 weeks. The exercise included single-leg standing, squatting, marching, and heel touching; and targeted balance, strength, locomotion/agility, and motor processing. MAIN OUTCOME MEASURES: single-leg balance with eyes open/closed and functional reach as balance, hand-grip strength and keeping a half-squat position as strength, walking time around two cones and 3-minute walking distance as locomotion/agility, and hand-reaction time and foot tapping as motor processing. RESULTS: at the pre-test, both exercise and control groups performed similarly in all tests. At the end of the intervention, the exercise group showed significantly greater single-leg balance with eyes closed, functional reach, and walking time around two cones. In contrast, there were no significant improvements in any of the test measures in the control group. CONCLUSIONS: dance-based aerobic exercise specifically designed for older women may improve selected components of balance and locomotion/agility, thereby attenuating risks of falling.

Rate of perceived exertion as a tool to monitor cycling exercise intensity in older adults.

The purpose of this study was to determine the efficacy of rate of perceived exertion (RPE) to monitor exercise intensity in older adults. Middle-aged (46.9 +/- 7.0 years, n = 24) and older women (75.5 +/- 3.8 years, n = 29) performed a graded maximal exercise test on a cycle ergometer while RPE, oxygen uptake, heart rate, and blood lactate levels were measured. The Pearson's product moment correlation coefficient between RPE and oxygen uptake for each stage of the graded exercise test was calculated for each participant. The mean coefficient for the older group (r =.954) was similar to that of middle-aged group (r =.963). The autocorrelation coefficient was much lower (r =.411) in the older group than in the middle-aged group (r =.871). Variability in RPE through the graded exercise test was similar between the two groups. In conclusion, RPE was strongly associated with oxygen uptake in the older group. These results indicate that RPE is effective in monitoring exercise intensity in older adults.