Acute effects of walking in water on vascular endothelial function and heart rate variability in healthy young men

Aim: Aquatic exercise might improve endothelial function due to hydrostatic pressure increasing blood flow and causing shear stress to the endothelium. However, the acute effect of aerobic exercise in water on endothelial function is unclear. The present study compares the acute effect of aerobic exercise at moderate intensity in water and on land on endothelial function.

Methods: Nine healthy young men walked on a treadmill for 30 min while immersed in water up to the xiphoid at 30.0 ± 0.2°C and on land at an intensity equivalent to 60% heart rate reserve in a crossover trial. Brachial artery flow-mediated dilation (FMD) was measured at baseline and at 30 and 60 min after exercise. Autonomic nervous activity was compared among conditions at the heart rate variability (HRV) during exercise.

Results: FMD significantly decreased at 30 min after exercise on land trial (p < 0.05), but did not change after the aquatic trial. However, FMD was significantly higher after aquatic trial than land trial (p < 0.05) at 30 and 60 min after exercise, whereas heart rate, blood pressure, and HRV did not significantly differ between them.

Conclusion: These findings demonstrate that aerobic exercise in water suppressed the decrease in FMD compared with that on land, regardless of autonomic nervous activity.     

Blood pressure and autonomic responses following isolated and combined aerobic and resistance exercise in hypertensive older women

Purpose: This study aimed to compare blood pressure (BP) after isolated and combined sessions of aerobic and resistance exercises in hypertensive older women. Heart rate (HR) and heart rate variability (HRV) were included as additional variables. Methods: Twenty-one older women (63±1.9 years; 69.9±2.7 kg; 158.8±2.1 cm) with controlled hypertension (resting BP = 132.2 ± 3.1/74.1 ± 4.0 mmHg) performed four random sessions on different days: 1) aerobic exercise (AE: treadmill walking/running; 40 min; 50–60% HR_reserve); 2) resistance exercise (RE: 8 exercises; 3 sets; 15 reps; 40% 1RM)); 3) aerobic exercise followed by resistance exercise (A+R); 4); control (CON). BP, HR and HRV were measured at rest and during 180 min after the sessions. Results: The AE and A+R sessions demonstrated significant decreases in SBP and DBP (30, 60, 120, and 180 min; P < 0.05) and increases in HR (30 and 60 min; P < 0.05) compared to the CON. The RE session demonstrated significant reductions compared to the CON only for DBP (120 and 180 min; P < 0.05). No significant differences were observed in HRV between resting and all sessions. Conclusion: All sessions that involved aerobic exercise (AE and A+R) caused postexercise hypotension in comparison to the CON, with no differences in HRV.     

The effects of exercise intensity on post exercise hypotension.

Ten normotensive, recreationally active participants aged 35.0 +/- 16.3 years, volunteered to participate in the study. Average baseline blood pressure (BP) was 132/75 mm Hg for systolic (SBP) and diastolic (DBP) pressure respectively. On two separate days, participants underwent testing in a randomised, repeated measures fashion such that they performed 30-min bouts of cycle ergometry at a power output which elicited 50 or 75% of VO2 Peak. Blood pressure was monitored continuously throughout the session by the Finapres method with 2-min windows recorded at rest, 5, 10, 15, 30, 45 and 60 min post exercise. SBP was similar between the two trials and became hypotensive at 5 through 15 min post exercise. The largest decrement (8 mm Hg) in SBP occurred 5 min post exercise. DBP was also unaffected by the intensity of exercise and was lower than before exercise at 5 and 15 through 45 min post exercise. Similarly, mean arterial pressure (MAP) showed significant decrements at 5 and 15 through 45 min post exercise irrespective of exercise intensity. Heart rate was greater during the 75% intensity than during the 50% intensity trial. Pre-exercise values were re-established by 45 min post exercise. VO2 remained significantly elevated above pre-exercise values in both trials until 15 min post exercise. Haematocrit increased significantly during both exercise bouts but returned to pre-exercise values by 10 min post exercise. This study indicates that cycle ergometry at 50 and 75% of VO2 Peak elicit similar reductions in post exercise BP. Therefore bouts of mild to moderate intensity exercise may be beneficial in the control of hypertension.     

Glucose and insulin responses following 16 months of exercise training in overweight adults: the Midwest Exercise Trial

The current study examined the insulin and glucose response during an oral glucose tolerance test (OGTT) in overweight young adults prior to and following exercise training in the Midwest Exercise Trial (MET). Subjects (N = 66) were randomly assigned to non-exercise control (CON; 16 females, 13 males) or exercise (EX; 22 females, 15 males) groups. EX performed supervised and verified exercise on 3 to 5 days per week in 20- to 45-minute sessions at 60% to 75% of heart rate reserve. OGTTs and assessments for body mass, body composition, and maximal oxygen consumption (Vo(2) max) were performed at baseline, and after 9 and 16 months of training. Blood was collected during a 75-g OGTT and analyzed for glucose and insulin concentrations with the total area under the glucose and insulin curves used in the analysis. The EX males had significant decreases from baseline to 9 months in body mass (94.8 +/- 12.5 to 89.2 +/- 9.8 kg) and percent fat (28.3 +/- 4.8 to 24.2 +/- 3.9) with no further changes at 16 months. CON females had significant increases in body mass (78.2 +/- 6.4 to 81.1 +/- 8.1 kg) and percent fat (36.6 +/- 4.2 to 37.8 +/- 4.7) from baseline to 16 months. Vo(2) max increased significantly from baseline to 9 months in the EX males (3.67 +/- 0.62 to 4.36 +/- 0.55 L/min) and EX females (2.53 +/- 0.32 to 2.99 +/- 0.42 L/min). For glucose area under the curve, there were no significant differences between EX or CON across the 16 months of the study. For insulin area under the curve, there was a significant decrease for male EX from baseline to 9 months (12,535 +/- 6,114 to 8,390 +/- 4,231 microU/L/180 min). We conclude that regular exercise in healthy, previously sedentary overweight adult males leads to improvements in Vo(2) max and weight loss and a reduction in the insulin concentration required to dispose of a set glucose load. In females, improvement in Vo(2) max without weight loss does not lead to improvement in insulin sensitivity.     

Effects of oral contraceptives on glucoregulatory responses to exercise

Some of the effects of oral contraceptives (OCs) to alter glucoregulation may be ameliorated by exercise. To test this premise, the effects of acute aerobic exercise on postprandial glucose, insulin, and C-peptide responses (area under the curve [AUC]) were measured in 8 users of low-dose estrogen and progestin OCs (OC(+)) and 10 women not using OCs (OC(-)). They completed 2 randomly ordered intervention trials: (1) aerobic exercise on 3 consecutive days with a 2.5-hour, 75-g oral glucose tolerance test (OGTT) on day 4, and (2) no exercise for 3 days prior to the OGTT (control trial). The exercise was 50 minutes of treadmill walking at 70% (.-)VO(2max). The groups were similar in age (27 +/- 3 years), waist-to-hip ratio (0.74 +/- 0.01), and cardiorespiratory fitness (32.5 +/- 1.6 mL x kg body mass(-1) x min(-1)). Fasting plasma glucose, C-peptide, and insulin levels were similar (P >.05) between groups in the control trial. In both trials, glucose(AUC) was significantly greater (13%, P <.05) in OC(+). Exercise resulted in a significant (P <.05) decrease in fasting plasma glucose and insulin, insulin(AUC), glucose(AUC) x insulin(AUC), and C-peptide(AUC) in both groups, suggesting enhanced insulin action and/or reduced pancreatic insulin secretion. Hepatic insulin extraction ([C-peptide(AUC) - insulin(AUC)())]/C-peptide(AUC)) was increased following exercise only in OC(+). Thus, insulin action was enhanced in response to exercise in young sedentary women independent of OC use. The mechanisms for the acute exercise effect on insulin action may be different in OC users compared with normally menstruating women.     

Taekwondo training reduces blood catecholamine levels and arterial stiffness in postmenopausal women with stage-2 hypertension: randomized clinical trial

Objective: Menopause is associated with a progressive impairment of vascular function and muscular strength in women. Accordingly, the purpose of this study was to determine if Taekwondo training could improve blood catecholamine levels, arterial stiffness, blood pressure (BP) and skeletal muscle strength in postmenopausal women with stage-2 hypertension.

Methods: 20 postmenopausal women (70 ± 4 years old) with stage-2 hypertension were randomly assigned to a 1) Taekwondo training (TT; n = 10) or 2) Control (CON; n = 10) group. Taekwondo training was performed for 60 minutes/day, 3 days/week for 12-weeks.

Results: There were significant (P < 0.05) group by time interactions for resting epinephrine (EP) and norepinephrine (NE) levels, with EP decreasing in the TT group and NE increasing in the CON group. Additionally, brachial-ankle pulse wave velocity, resting heart rate, and BP were significantly decreased, while hand grip and leg strength were significantly increased in the TT group compared to CON group.

Conclusion: These results suggest that Taekwondo training can be a novel and beneficial mode of exercise for improving cardiovascular function and muscular strength in this population.

Abbreviations: TT: Taekwondo training group; CON: control group; EP: epinephrine; NE: norepinephrine; ANS: autonomic nervous system; SNS: sympathetic nervous system; baPWV: brachial-ankle pulse wave velocity     

Aerobic exercise training normalizes central blood pressure regulation after oral glucose loading in overweight/obese men

Central systolic blood pressure (cSBP) decreases after a meal or glucose challenge, but this response is impaired in obesity-related disorders. We investigated whether aerobic exercise training improves cSBP regulation during an oral glucose tolerance test (OGTT) in overweight/obese men. Thirteen overweight/obese men and six normal-weight men (as an alternative comparison instead of a no-exercise group) completed a 12-week aerobic exercise training program. Before and after the program, cSBP (i.e., radial second systolic pressure) was measured using an applanation tonometry at fasting and both 60 min and 120 min after 75 g glucose loading. Before and during the program, physical activity (PA) time was recorded using a tri-axial accelerometer. Pre-training, cSBP was significantly decreased with glucose loading in normal-weight men, while cSBP did not change in overweight/obese men. Post-training, a significant decrease in cSBP was observed in both groups following glucose loading. In addition, the increase in vigorous PA time during the exercise program was significantly correlated to the increase in area above the curve for cSBP during OGTT (demonstrating an improvement in the cSBP response to glucose loading) after the exercise program. These findings may provide novel insights into the role of PA in reducing the cardiovascular risk in obesity.     

Dilution of the 75-g oral glucose tolerance test improves overall tolerability but not reproducibility in subjects with different body compositions

Poor reproducibility of the 75-g oral glucose tolerance test (75-g OGTT) is a major criticism. To test whether dilution might be a contributor, we studied the effect of administering it at 300, 600, and 900 ml on the coefficient of variation (CV) and overall tolerability. Each dilution was randomly repeated three times by 35 subjects: 11 lean (body fat [BF]: 11.5+/-1.5%, body mass index (BMI): 24.1+/-0.8 kg/m(2), age: 33+/-3 years), 12 normal (BF: 24.3+/-1.3%, BMI: 23.9+/-0.7 kg/m2, age: 33+/-3 years), and 12 obese (BF: 34.1+/-1.5%, BMI: 34.5+/-1.6 kg/m(2), age: 41+/-4 years). The protocol followed, the American Diabetes Association (ADA) guidelines with venous samples drawn at 0, 15, 30, 45, 60, 90, and 120 min. Scales assessing palatability, acceptability, satiety, nausea, and dizziness were also completed. No differences were detected in CV between the three dilutions at the 2 h-diagnostic-endpoint in any group. CV for glycemia, however, was lower for the 300-ml OGTT (10+/-2.1%) than either the 600 ml (17.9+/-2.1%) or 900-ml OGTT (19.9+/-4.4%) at 45 min in the lean group (P<0.05). CV for insulinemia was lower for the 300 ml (30.6+/-4.5%) and 600 ml (30.6+/-4.1%) OGTT than the 900-ml OGTT (53.7+/-7.9%) at 60 min in the obese group (P<0.05). When affective ratings were compared, the 600-ml OGTT scored highest on palatability and acceptability (P<0.05). We concluded that the dilution of the 75-g OGTT improves the overall tolerability but not reproducibility of results. Practitioners may choose to give it at the best-tolerated dilution.     

Supervised home-based exercise may attenuate the decline of glucose tolerance in obese pregnant women

AimThe significant deterioration of insulin sensitivity and glucose tolerance during pregnancy can have serious health implications for both the pregnant woman and her baby. Although it is well established that regular exercise benefits insulin sensitivity in the nonpregnant population, the effect on glucose tolerance in obese pregnant women is not known. The purpose of this study was to investigate the effect of a supervised 10-week, home-based, exercise programme, beginning at week 18 of gestation, on glucose tolerance and aerobic fitness in previously sedentary obese women.MethodsTwelve sedentary obese women were randomized into an exercise (EX; n = 6) or control (CON; n = 6) group at 18 weeks of gestation. Those randomized to EX engaged in 10 weeks of supervised home-based exercise (three sessions a week of stationary cycling), while those in the CON group maintained their usual daily activity. Their glucose and insulin responses to an oral glucose tolerance test (OGTT), as well as their aerobic fitness, were assessed both pre- and postintervention.ResultsReduced glucose tolerance in the CON, but not EX, group was indicated by a tendency postintervention towards higher blood glucose levels at 1 h of the OGTT (P = 0.072). Furthermore, at 2 h of the postintervention OGTT, blood glucose tended to remain elevated from baseline in the CON (P = 0.077). There was also a trend towards increased fitness in the EX (P = 0.064), but not the CON group.ConclusionRegular aerobic exercise begun during pregnancy may have favourable effects on glucose tolerance and fitness in obese women, and warrants further investigation in a larger sample population.     

Association between handgrip strength and vascular function in patients with hypertension

Background: Increased handgrip strength has been associated with lower cardiovascular and non-cardiovascular mortality in different populations. In patients with hypertension, arterial stiffness relates to cardiovascular mortality. However, whether muscle strength is associated with arterial stiffness in hypertensives is unknown. Thus, the objective of this study was to analyze the association between handgrip strength and arterial stiffness parameters in hypertensive patients.

Methods: Seventy-two hypertensive patients completed all evaluations and were included in the analysis. The ambulatory arterial stiffness index (AASI) was obtained based on 24-h ambulatory blood pressure monitoring. Carotid-femoral pulse wave velocity (cfPWV), and reflected wave indicator (AIx and AIx@75) were estimated using applanation tonometry technique, whereas handgrip strength test was performed using a digital dynamometer. Crude and adjusted linear regression models were performed.

Results: The crude analysis revealed a negative association between handgrip strength and AASI (b = ?0.41, p = 0.002) and AIx (b = ?0.49, p < 0.001), and AIx@75 (b = ?0.54, p < 0.001) which remained significant after adjustments for age, sex, and body mass index, mean blood pressure, and heart rate only for AASI (b = ?0.46, p = 0.028) and AIx@75 (b = ?0.24, p- = 0.040). Handgrip strength was not associated with cfPWV (p > 0.05).

Conclusion: Handgrip strength is negatively associated with AASI and AIx@75, but not with AIx and cfPWV in hypertensive patients.     

Effect of acute and long-term aerobic exercise on arterial stiffness in the elderly.

Arterial stiffness is an important factor for cardiovascular performance and a predictor of cardiovascular risk. We evaluated the effects of both acute and long-term aerobic exercise on arterial stiffness in community-dwelling healthy elderly subjects. In addition, we evaluated the relationship between the effects of long-term exercise and those of acute exercise. The study subjects were participants in the Shimanami Health Promoting Program study (J-SHIPP), which was designed to investigate factors relating to cardiovascular disease, dementia, and death (67+/-6 years). They performed mild-to-moderate aerobic exercise lasting for 30 min twice a week for 6 months. Arterial stiffness was assessed before and after the first 30-min acute exercise (n=99) and long-term 6-month aerobic training (n=40). The radial arterial augmentation index (AI) obtained from the radial pulse waveform by the tonometry method was used as a parameter of arterial stiffness. Both systolic blood pressure (SBP) and diastolic blood pressure (DBP) were significantly decreased after 30-min of aerobic exercise, however no significant change in AI was observed. On the other hand, there were significant decreases in AI (from 87 to 84%, p<0.01), SBP (from 136 to 129 mmHg, p<0.01), and DBP (from 75 to 70 mmHg, p<0.01) after the 6-month exercise period. Long-term exercise-induced changes in AI were significantly and inversely correlated with the pre-exercise AI (r=-0.40, p<0.01). In addition, AI changes after the 6-month exercise period were significantly related to those observed after first 30-min exercise (r=0.48, p<0.01). These findings indicate that apparently healthy and sedentary elderly subjects with higher AI may benefit from mild-to-moderate aerobic exercise to improve arterial stiffness.     

Prior exercise potentiates the thermic effect of a carbohydrate load

It is unclear whether dietary-induced thermogenesis (DIT) is increased after exercise. To test this possibility, six healthy volunteers, male and female, exercised for 45 minutes at 70% of maximal aerobic capacity (VO2 max) in the morning after an overnight fast. Two hours after the end of the exercise, by which time VO2 had returned to near baseline levels, subjects ingested a 100-g glucose load. Blood samples and respiratory gas exchange data were collected over the next three hours. On a separate day on which the subjects did not exercise, the test procedure was repeated. Glucose tolerance and the insulin response to the glucose load were not significantly different between the two trials; however, VO2 increased by 15.5% over baseline on the exercise day, compared with only 8.9% when exercise was not performed. The net increase in energy expenditure for the three-hour period following glucose ingestion was 15 kcal/180 min greater on the exercise than on the control day, with increases upwards of 20 kcal/180 min in several individuals. No correlation was found between the magnitude of exercise-enhanced DIT and VO2 max, suggesting that this effect is independent of the state of training. The results indicate that the thermic effect of exogenous carbohydrate can be potentiated by prior exercise.     

Ghrelin and other glucoregulatory hormone responses to eccentric and concentric muscle contractions

Objective: Heavy resistance exercise increases growth hormone (GH) and blood glucose levels. Ghrelin is an endogenous ligand for the GH secretagory receptor that stimulates growth hormone release. Circulating ghrelin levels are suppressed by insulin and glucose. The study was conducted to determine effects of concentric (CON) and eccentric (ECC) muscle actions at the same absolute workload on circulating ghrelin and glucose as well as related glucoregulatory peptides. Methods: Ten-RM loads for bench press, leg extension, military press, and leg curl were obtained from nine males, mean age 25.±1.2 yr and body fat 17.2±1.6%. Subjects then completed two experimental trials of either CON or ECC contractions at the same absolute workload. Subjects performed four sets of 12 repetitions for each exercise at 80% of a 10-RM with 90 s rest periods. A pulley system or steel levers were positioned on each machine to raise or lower the weight so only CON or ECC contractions were performed. Pre-, post-, and 15-min post-exercise blood samples were collected. Results: Ghrelin did not increase in response to either muscle action and actually declined during the CON trial. Glucose and insulin increased regardless of the form of muscle action, but amylin and C-peptide did not change. Conclusions: Data indicate that ghrelin does not contribute to moderate resistance exercise-induced increases in growth hormone, whether from CON or ECC muscle actions. Results suggest that with a moderate loading protocol both CON and ECC muscle actions performed at the same absolute workload elevate glucose and insulin concentrations, but are not related to post-CON exercise ghrelin suppression.     

Seventy-five gram glucose tolerance test to assess carbohydrate malabsorption and small bowel bacterial overgrowth

AIM: To investigate non-invasively the incidence of absorption of carbohydrates in diabetic patients during an oral glucose tolerance test (OGTT) and to determine whether malabsorption may be associated with insulin secretion and insulin resistance. METHODS: A standard 75-g OGTT was performed in 82 diabetic patients. The patients received 75 g of anhydrous glucose in 225 mL of water after an overnight fasting and breath samples were collected at baseline and up to 120 min after ingestion. Breath hydrogen and methane concentrations were measured. Blood glucose and serum insulin concentrations were measured before ingestion and at 30, 60, 90, 120 min post-ingestion. RESULTS: When carbohydrate malabsorption was defined as subjects with an increase of at least 10 ppm (parts per million) in hydrogen or methane excretion within a 2-h period, 28 (34%) had carbohydrate malabsorption. According to the result of increased breath test, 21 (75%) patients were classified as small bowel bacterial overgrowth and 7 (25%) as glucose malabsorption. Patients with carbohydrate malabsorption were older and had poor glycemic control as compared with those without carbohydrate malabsorption. The HOMA value, the sum of serum insulin during the test and the Ainsulin/Aglucose ratio were greater in patients with carbohydrate malabsorption. CONCLUSION: Insulin resistance may be overestimated by using these markers if the patient has carbohydrate malabsorption, or that carbohydrate malabsorption may be present prior to the development of insulin resistance. Hence carbohydrate malabsorption should be taken into account for estimating insulin resistance andβ-cell function.     

Cardiac autonomic recovery in response to aerobic versus resistance exercise in type 2 diabetes mellitus patients

Purpose

To investigate the effect of aerobic exercise (AE) versus resistance exercise (RE) on outcomes of cardiac autonomic recovery in type 2 diabetes mellitus (T2DM) patients with cardiac autonomic neuropathy (CAN).

Methods

Fifty T2DM patients with CAN (age: 52.2 ± 6.8 years) were recruited for the present study. They were randomly allocated into two groups: AE (n = 25) and RE (n = 25). The AE group performed graded maximal exercise test using Balke protocol while the RE group performed 5 sets of leg press exercise at 10 repetition maximum (RM) intensity. Heart rate variability (HRV) was assessed for 10 min after both exercise bouts while heart rate recovery (HRR) was recorded for the first 3 min after completion of the exercise bouts. Key outcome measures for the study were standard time and frequency domain parameters of HRV and HRR_1min, HRR_2min, and HRR_3min. Standard statistical analysis which included independent t-test and repeated measures analysis of variance was performed in order to test the study hypothesis.

Results

Significant impairment was observed in both HRV and HRR after both AE and RE (p < 0.05). However, alterations in both HRV and HRR responses were found to be more after AE as compared to RE (p < 0.05) in T2DM patients with CAN.

Conclusion

Findings of the present study suggest significant blunting of autonomic responses after both AE and RE in T2DM patients with CAN. However, deterioration in them was found to be more after AE as compared to the RE indicating that AE may pose greater stress on the cardiovascular system of T2DM patients with CAN.

     

The effect of 4 weeks of aerobic exercise on vascular and baroreflex function of young men with a family history of hypertension

The effect of short-term aerobic exercise on vascular function of young individuals with a family history of hypertension was investigated. Thirty young men with a family history of hypertension were randomly assigned to either an exercise (n=15) or control (n=15) group. Exercise subjects performed 30?min of supervised cycle training at 65% of their maximal oxygen uptake (\[Vdot]O(2max)), three times per week for 4 weeks. Control subjects were asked to maintain their normal levels of physical activity. Peak leg and forearm blood flow were assessed using plethysmography and was determined as the highest blood flow following 5?min of reactive hyperemia. Cardiopulmonary baroreceptor (CPBR) sensitivity was measured using lower body negative pressure (LBNP) for 5?min at -20?mm?Hg. CPBR was determined by calculating change of stroke volume and forearm vascular resistance at baseline and during LBNP. Carotid baroreceptor (CBR) sensitivity was assessed using neck suction at -20, -40, -60 and -80?mm?Hg pressures, and was determined from RR interval divided by systolic blood pressure. Augmentation index (AIx), a measure of arterial stiffness, was assessed using applanation tonometry and was calculated as the ratio of augmented pressure and pulse pressure. The major findings were that the exercise group showed increase in leg vasodilation, reduction in AIx and increase in \[Vdot]O(2max) compared with the control group (P<0.05). However, there was no significant change for CPBR and CBR. A short-term moderate-intensity aerobic exercise intervention in young men with a family history of hypertension significantly reduced arterial stiffness and increased aerobic fitness.     

Effect of 4 weeks of aerobic or resistance exercise training on arterial stiffness, blood flow and blood pressure in pre- and stage-1 hypertensives

The benefits of aerobic exercise (AE) training on blood pressure (BP) and arterial stiffness are well established, but the effects of resistance training are less well delineated. The purpose of this study was to determine the impact of resistance vs aerobic training on haemodynamics and arterial stiffness. Thirty pre- or stage-1 essential hypertensives (20 men and 10 women), not on any medications, were recruited (age: 48.2 +/- 1.3 years) and randomly assigned to 4 weeks of either resistance (RE) or AE training. Before and after training, BP, arterial stiffness (pulse wave velocity (PWV)) and vasodilatory capacity (VC) were measured. Resting systolic BP (SBP) decreased following both training modes (SBP: RE, pre 136 +/- 2.9 vs. post 132 +/- 3.4; AE, pre 141 +/- 3.8 vs. post 136 +/- 3.4 mm Hg, P = 0.005; diastolic BP: RE, pre 78 +/- 1.3 vs post 74 +/- 1.6; AE, pre 80 +/- 1.6 vs. post 77 +/- 1.7 mm Hg, P = 0.001). Central PWV increased (P = 0.0001) following RE (11 +/- 0.9-12.7 +/- 0.9 ms(-1)) but decreased after AE (12.1 +/- 0.8-11.1 +/- 0.8 m s(-1). Peripheral PWV also increased (P = 0.013) following RE (RE, pre 11.5 +/- 0.8 vs. post 12.5 +/- 0.7 ms(-1)) and decreased after AE (AE, pre 12.6 +/- 0.8 vs post 11.6 +/- 0.7 m s(-1)). The VC area under the curve (VC(AUC)) increased more with RE than that with AE (RE, pre 76 +/- 8.0 vs. post 131.1 +/- 11.6; AE, pre 82.7 +/- 8.0 vs. post 110.1 +/- 11.6 ml per min per s per 100 ml, P = 0.001). Further, peak VC (VCpeak) increased more following resistance training compared to aerobic training (RE, pre 17 +/- 1.9 vs. post 25.8 +/- 2.1; AE, pre 19.2 +/- 8.4 vs post 22.9 +/- 8.4 ml per min per s per 100 ml, P = 0.005). Although both RE and AE training decreased BP, the change in pressure may be due to different mechanisms.     

Effect of exercise on postprandial insulin responses in Mexican American and non-Hispanic women.

Postprandial insulin responses (integrated area under the curve) to an oral glucose load after a period of aerobic exercise and no exercise (control) were compared in sedentary normoglycemic Mexican American and non-Hispanic women pair-matched (n = 9) on total body fat mass (21.8 +/- 3.5 kg). The age (27.4 +/- 3.0 years), body mass index (BMI) (23.6 +/- 1.4 kg/m2), waist to hip ratio (WHR) (0.85 +/- .02), waist circumference (83.5 +/- 4.5 cm), lean mass (36.2 +/- 1.5 kg), and maximal O2 consumption ([VO2 max] 32.9 +/- 1.6 mL x kg(-1) x min(-1)) were similar, although the centrality index (subscapular/triceps skinfolds) was significantly greater in Mexican Americans (0.88 +/- 0.06 v 0.70 +/- 0.05, P < .01). Exercise (treadmill walking for 50 minutes at 70% VO2 max) and control trials were performed 4 weeks apart and 5 to 12 days after the onset of menstruation. A 75-g oral glucose load was administered 15 hours after the completion of each trial, with the subjects 12 hours postprandial. Blood samples were drawn prior to glucose ingestion (fasting, 0 minutes) and at minutes 15, 30, 60, 90, 120, and 150 postingestion. The postprandial insulin response was calculated using a trapezoidal method. In Mexican Americans, significant (P < .02) reductions in the postprandial insulin response (exercise v control, 6.5 +/- 1.0 v 8.5 +/- 1.4 pmol/L x min x 10(4)) and fasting insulin (exercise v control, 77.4 +/- 7.0 v 88.5 +/- 10.3 pmol/L) occurred after exercise compared with the control condition. In non-Hispanics, neither the postprandial insulin response (exercise v control, 7.2 +/- 1.0 v 6.2 +/- 0.9 pmol/L x min x 10(4)) nor fasting insulin (exercise v control, 77.0 +/- 8.2 v 82.9 +/- 8.9 pmol/L) were significantly different between trials. The postprandial insulin response in the control trial was significantly correlated with the change in the insulin response (control minus exercise) in the 18 women (r = .56, P = .01). No trial or group differences were found for postprandial glucose and C-peptide responses. Mexican American women have a high risk of developing type 2 diabetes, and aerobic exercise may be valuable in the prevention or delay of onset of diabetes by reducing peripheral insulin resistance.     

Post-challenge hyperglycaemia is an independent risk factor for arterial stiffness in Japanese men.

AIMS: Arterial stiffness is an independent predictor of cardiovascular disease, but the impact of post-challenge hyperglycaemia on arterial stiffness is unknown. To investigate the association between arterial stiffness and post-challenge hyperglycaemia, we measured the second derivative of photoplethysmogram as an indicator of arterial stiffness. METHODS: This study was done in 159 asymptomatic Japanese men aged 50.7 +/- 13.0 years. All subjects underwent a 75-g oral glucose tolerance test and measurement of the second derivative of photoplethysmogram. RESULTS: According to the World Health Organization criteria (1998), 110 subjects had normal glucose tolerance, 10 had impaired fasting glucose, 30 had impaired glucose tolerance, and nine had diabetes. The b/a ratio (an index of arterial stiffness) showed a significant relationship with age (r = 0.58, P < 0.0001), height (r = -0.33, P < 0.0001), 2-h post-challenge glucose (r = 0.32, P < 0.0001), systolic blood pressure (r = 0.22, P = 0.006), and diastolic blood pressure (r = 0.21, P = 0.009). After adjustment for age and height, there were significant correlations between the b/a ratio and diastolic blood pressure (r = 0.18, P = 0.02), fasting glucose (r = 0.16, P = 0.049), and 2-h post-challenge glucose (r = 0.21, P = 0.009). Stepwise multiple regression analysis showed that only age (beta= 0.006, SE = 0.0007, P < 0.001) and 2-h post-challenge glucose (beta = 0.0005, SE = 0.0002, P < 0.05) contributed significantly to the b/a ratio (adjusted R(2) = 0.38). CONCLUSIONS: These results indicate that post-challenge hyperglycaemia is an independent risk factor for arterial stiffness.     

Changes of central haemodynamic parameters during mental stress and acute bouts of static and dynamic exercise

Chronic dynamic (aerobic) exercise decreases central arterial stiffness, whereas chronic resistance exercise evokes the opposite effect. Nevertheless, there is little information available on the effects of acute bouts of exercise. Also, there is limited data showing an increase of central arterial stiffness during acute mental stress. This study aimed to determine the effect of acute mental and physical (static and dynamic exercise) stress on indices of central arterial stiffness. Fifteen young healthy volunteers were studied. The following paradigms were performed: (1) 2 min of mental arithmetic, (2) short bouts (20 s) of static handgrip at 20 and 70% of maximal voluntary contraction (MVC), (3) fatiguing handgrip at 40% MVC and (4) incremental dynamic knee extensor exercise. Central aortic waveforms were assessed using SphygmoCor software. As compared to baseline, pulse wave transit time decreased significantly for all four interventions indicating that central arterial stiffness increased. During fatiguing handgrip there was a fall in the ratio of peripheral to central pulse pressure from 1.69+/-0.02 at baseline to 1.56+/-0.05 (P<0.05). In the knee extensor protocol a non-significant trend for the opposite effect was noted. The augmentation index increased significantly during the arithmetic, short static and fatiguing handgrip protocols, whereas there was no change in the knee extensor protocol. We conclude that (1) during all types of acute stress tested in this study (including dynamic exercise) estimated central stiffness increased, (2) during static exercise the workload posed on the left ventricle (expressed as change in central pulse pressure) is relatively higher than that posed during dynamic exercise (given the same pulse pressure change in the periphery).