Sushant M. Ranadive

Muscular strength is inversely associated with aortic stiffness in young men.

UNLABELLED Muscular strength is associated with reduced mortality. Paradoxically, strength training may increase central artery stiffness, a predictor of cardiovascular morbidity and mortality. However, the relationship between muscular strength and central arterial stiffness has yet to be defined. PURPOSE The purpose of this study was to determine the relationship between muscular strength and central arterial stiffness in young men. METHODS Central and peripheral pulse wave velocity (PWV), augmentation index, muscular strength, and aerobic capacity (V O2peak) were measured in 79 young men (mean +/- SD, age = 23 +/- 4 yr). Height, weight, and brachial blood pressure were also recorded. Muscular strength was determined using a one-repetition maximum bench press and normalized to bodyweight. Spearman correlations were used to determine the relationships between relative strength, aerobic fitness, and hemodynamic/vascular measures. RESULTS There was a significant negative correlation between central PWV and strength (r = -0.222, P < 0.05). The relationship remained significant when controlling for aerobic fitness (r = -0.189, P < 0.05). Muscular strength was significantly higher (P < 0.05) in men with low central PWV (5.2 +/- 0.4 m.s) compared with men with high central PWV (6.6 +/- 0.4 m.s). CONCLUSION These results show that there is a significant inverse association between muscular strength and aortic stiffness independent of aerobic fitness.

Postexercise Hypotension in an Endurance-Trained Population of Men and Women Following High-Intensity Interval and Steady-State Cycling

BACKGROUND The acute effect of high-intensity interval exercise (HI) on blood pressure (BP) is unknown although this type of exercise has similar or greater cardiovascular benefits compared to steady-state aerobic exercise (SS). This study examined postexercise hypotension (PEH) and potential mechanisms of this response in endurance-trained subjects following acute SS and HI. Sex differences were also evaluated. METHODS A total of 25 endurance-trained men (n = 15) and women (n = 10) performed a bout of HI and a bout of SS cycling in randomized order on separate days. Before exercise, 30 min postexercise, and 60 min postexercise, we measured brachial and aortic BP. Cardiac output (CO), stroke volume (SV), end diastolic volume (EDV), end systolic volume (ESV), and left ventricular wall-velocities were measured using ultrasonography with tissue Doppler capabilities. Ejection fraction and fractional shortening (FS), total peripheral resistance (TPR), and calf vascular resistance were calculated from the above variables and measures of leg blood flow. RESULTS BP, ejection fraction, and FS decreased by a similar magnitude following both bouts but changes in CO, heart rate (HR), TPR, and calf vascular resistance were greater in magnitude following HI than following SS. Men and women responded similarly to HI. Although men and women exhibited a similar PEH following SS, they showed differential changes in SV, EDV, and TPR. CONCLUSIONS HI acutely reduces BP similarly to SS. The mechanistic response to HI appears to differ from that of SS, and endurance-trained men and women may exhibit differential mechanisms for PEH following SS but not HI.

Acute effects of firefighting on arterial stiffness and blood flow.

Sudden cardiac events are responsible for 40—50% of line-of-duty firefighter fatalities, yet the exact cause of these events is unknown. Likely, combinations of thermal, physical, and mental factors impair cardiovascular function and trigger such events. Therefore, the purpose of this study was to examine the impact of firefighting activities on vascular function. Sixty-nine young (28 ± 1 years) male firefighters underwent 3 hours of firefighting activities. Carotid, aortic, and brachial blood pressures (BP), heart rate (HR), augmentation index (AIx), wave reflection timing (TR), aortic pulse wave velocity (PWV), forearm blood flow (FBF), and forearm reactive hyperemia (RH) were measured before and after firefighting activities. Paired samples t-tests revealed significant (p < 0.05) increases in aortic diastolic BP, HR, AIx, PWV, RH, and FBF, and significant decreases in brachial and aortic pulse pressure and TR following firefighting activities. In conclusion, these results suggest that 3 hours of firefighting activities increase both arterial stiffness and vasodilation.

Vascular dysfunction and physical activity in multiple sclerosis.

BACKGROUND Multiple sclerosis (MS) is an inflammatory disorder of the brain and spinal cord. Disability status and progression are associated with reduced physical activity (PA) and cardiovascular function. Lack of adequate PA combined with inflammation may create high susceptibility to subclinical atherosclerosis and vascular dysfunction. PURPOSE The purpose of this study was to compare subclinical atherosclerosis and arterial function between individuals with and without MS matched for age, sex, and body mass index. METHODS Thirty-three individuals diagnosed with MS and 33 controls underwent strain gauge plethysmography for resting forearm blood flow (FBF) and peak reactive hyperemia for the microvascular function. Intima-media thickness and arterial compliance (AC) were measured using carotid ultrasound for vascular function. C-reactive protein and PA (7-d accelerometer data) were also measured. RESULTS There was a significant difference (P < 0.05) in resting FBF, peak reactive hyperemia, central pulse wave velocity, and AC between the MS and control groups. PA was associated with peak FBF and central pulse wave velocity but not FBF and carotid AC. Individuals with MS exhibit reduced arterial function but similar intima-media thickness compared with controls. Persons with MS had significantly reduced PA levels compared with controls, and PA accounted for differences in arterial function between groups. CONCLUSIONS These results indicate that subclinical markers of atherosclerosis are higher in individuals with MS, suggesting a higher risk of cardiovascular disease in this population. However, the higher levels of subclinical atherosclerosis were accounted for by the low PA in persons with MS, suggesting that increasing PA may reduce the increase in cardiovascular disease risk in patients with MS.

Review Article: L-Arginine as a Nutritional Prophylaxis Against Vascular Endothelial Dysfunction With Aging

With advancing age, peripheral conduit and resistance arteries lose the ability to effectively dilate owing to endothelial dysfunction. This vascular senescence contributes to increased risk of cardiovascular disease (CVD) with aging. L-arginine plays a role in numerous physiological processes including nitrogen detoxification, immunocompetence, growth hormone (GH) secretion, and insulin secretion. Recently, a considerable amount of attention has been placed on the ability of this amino acid to affect vascular endothelial function. The purpose of this review will be to examine the use of L-arginine as a novel nutritional strategy to potentially stave progression of vascular dysfunction with aging and CVD. Emphasis will be placed on the ability of L-arginine to modulate the vascular inflammatory and systemic hormonal milieu, which in turn may have a positive effect on vascular endothelial function.

Contribution of nitric oxide in the contraction-induced rapid vasodilation in young and older adults

We tested the hypothesis that reduced nitric oxide (NO) bioavailability contributes to the attenuated peak and total vasodilation following single-muscle contractions in older adults. Young (n = 10; 24 ± 2 yr) and older (n = 10; 67 ± 2 yr) adults performed single forearm contractions at 10, 20, and 40% of maximum during saline infusion (control) and NO synthase (NOS) inhibition via N(G)-monomethyl-l-arginine. Brachial artery diameters and velocities were measured using Doppler ultrasound and forearm vascular conductance (FVC; in ml·min(-1)·100 mmHg(-1)) was calculated from blood flow (ml/min) and blood pressure (mmHg). Peak and total vasodilator responses [change (Δ) in FVC from baseline] were attenuated in older adults at all intensities (P < 0.05). NOS inhibition reduced the peak ΔFVC at 10% (88 ± 12 vs. 52 ± 9 ml·min(-1)·100 mmHg(-1)), 20% (125 ± 13 vs. 83 ± 13 ml·min(-1)·100 mmHg(-1)), and 40% (207 ± 26 vs. 133 ± 20 ml·min(-1)·100 mmHg(-1)) in young subjects, (P < 0.05 for all) and in older adults at 10% (59 ± 5 vs. 47 ± 7 ml·min(-1)·100 mmHg(-1), P < 0.05) and 20% (88 ± 9 vs. 68 ± 9 ml·min(-1)·100 mmHg(-1), P < 0.05), but not 40% (128 ± 12 vs. 105 ± 11 ml·min(-1)·100 mmHg(-1), P = 0.11). The relative (%) reduction in peak ΔFVC due to NOS inhibition was greater in young vs. older adults at 20% (-36 ± 5 vs. -23 ± 5%, P < 0.05) and 40% (-35 ± 6 vs. -16 ± 7%, P < 0.05). The reduction in the total vasodilator response (area under the curve) with NOS inhibition was also greater in young vs. older adults at all intensities. Our data suggest that contraction-induced rapid vasodilation is mediated in part by NO, and that the contribution of NO is greater in young adults.

Hemodynamic and arterial stiffness differences between African-Americans and Caucasians after maximal exercise

African-American (AA) men have higher arterial stiffness and augmentation index (AIx) than Caucasian-American (CA) men. Women have greater age-associated increases in arterial stiffness and AIx than men. This study examined racial and sex differences in arterial stiffness and central hemodynamics at rest and after an acute bout of maximal exercise in young healthy individuals. One hundred young, healthy individuals (28 AA men, 24 AA women, 25 CA men, and 23 CA women) underwent measurements of aortic blood pressure (BP) and arterial stiffness at rest and 15 and 30 min after an acute bout of graded maximal aerobic exercise. Aortic BP and AIx were derived from radial artery applanation tonometry. Aortic stiffness (carotid-femoral) was measured via pulse wave velocity. Aortic stiffness was increased in AA subjects but not in CA subjects (P < 0.05) after an acute bout of maximal cycling exercise, after controlling for body mass index. Aortic BP decreased after exercise in CA subjects but not in AA subjects (P < 0.05). Women exhibited greater reductions in AIx after maximal aerobic exercise compared with men (P < 0.05). In conclusion, race and sex impact vascular and central hemodynamic responses to exercise. Young AA and CA subjects exhibited differential responses in central stiffness and central BP after acute maximal exercise. Premenopausal women had greater augmented pressure at rest and after maximal aerobic exercise than men. Future research is needed to examine the potential mechanisms.

Effect of resistance training on biomarkers of vascular function and oxidative stress in young African-American and Caucasian men

African Americans (AA) have an earlier onset of hypertension and a different vascular profile than their Caucasian (Cau) peers. Research suggests that biological mediators of vascular inflammation are different among these groups in hypertensive populations. Resistance training (RT) is an important exercise modality that improves the vascular profile of young AA men. We examined the role of RT on biomarkers of vascular function and oxidative stress in body mass index-matched AA and Cau men. RT for 6 weeks elicited significant changes in circulating matrix metalloprotease-9 (MMP-9) and 8-Isoprostane (8-IsoP) in young AA men (n=14, AA; n=18, Cau; 18–35 years). MMP-9 was lower and decreased in AA (pre: P=0.02; post: P<0.001) and a time × group interaction for MMP-9 (F1, 30=4.81; P=0.036) and 8-IsoP (F1, 24=7.09; P=0.014) was detected. 8-IsoP decreased in AA (P=0.026) but did not change in Cau (P=0.309). Notably, the increase in strength (1-repetition maximum (1-RM)) was correlated with the decrease in MMP-9 (r=−0.398; P=0.022). Furthermore, these adaptations were independent of any improvement in cardiorespiratory fitness. We demonstrate that RT effectively reduces matrix remodeling proteins and oxidative stress in young AA men. Increasing strength may be beneficial for improving vascular health and offsetting novel cardiovascular risk factors of hypertension in young AA men.

Metabolic rate and accelerometer output during walking in people with Down syndrome.

UNLABELLED People with Down syndrome (DS) have reduced gait stability and aerobic fitness that increase the metabolic rate during walking, potentially altering the relationship between metabolic rate and accelerometer output and lowering predictability of energy expenditure from accelerometry. PURPOSE This study examined whether the relationship between metabolic rate and activity count rate differs between individuals with and without DS and whether predictability of metabolic rate is different between groups. METHODS Metabolic rate was measured in METs with portable spirometry in 18 subjects with DS (24.7±6.7 yr; 10 women) and 18 subjects without DS (26.3±5.2 yr; 10 women) during five overground walking trials, each lasting 6 min, at 0.5, 0.75, 1.0, 1.25, and 1.5 m·s. A uniaxial accelerometer secured at the right side of the hip allowed for the determination of activity count rate. RESULTS The relationship between METs and activity count rate in the two groups was analyzed with multilevel modeling with random intercepts and slopes, demonstrating a significant interaction between group and activity count rate (P<0.001). Separate models for each group showed that the activity count rate and its squared significantly predicted METs (P≤0.001). Actual and predicted METs did not differ in each group. Bland-Altman plots showed greater variability in the difference between actual and predicted METs for participants with DS. Mean absolute error of prediction was 19.92% and 14.55% for participants with and without DS, respectively. CONCLUSIONS Individuals with DS show altered METs to activity count rate relationship during overground walking and have lower predictability of metabolic rate from uniaxial accelerometer output than individuals without DS.

Pulse pressure is associated with walking impairment in multiple sclerosis

Persons with multiple sclerosis (MS) have reduced gait performance and this is associated with disability and disease progression. The current study sought to test the hypothesis that higher central (aortic and carotid) and peripheral (brachial) pulse pressure (PP), manifestations of ventricular-vascular uncoupling related to increased arterial stiffness and pressure from wave reflections, would be associated with reduced gait performance in persons with MS. Participants consisted of 33 individuals with MS and 33 age/sex matched controls. Central blood pressure (BP) was assessed via applanation tonometry. Brachial BP was measured using an automated oscillometric cuff. PP was defined as systolic BP--diastolic BP. Gait performance was measured as 6-minute walk (6 MW) distance. Within the sample with MS, the 6 MW distance was significantly associated with brachial (r = -.49, p<.005), aortic (r = -.52, p<.001), and carotid (r = -.57, p<.001) pulse pressure. There was no association between any PP measure and 6 MW distance in controls (p>0.05 for all). In conclusion, PP is a predictor of gait performance in persons with MS. These findings suggest that vascular senescence and altered ventricular-vascular coupling may contribute, in part, to the deterioration of physical function in persons with MS.