Association between cardiac high-energy phosphate metabolism and whole body metabolism in healthy female adults.

Decline in cardiac high-energy phosphate metabolism [phosphocreatine-to-ATP (PCr/ATP) ratio] and whole body metabolism increase the risk of heart failure and metabolic diseases. The aim of the present study was to assess the relationship between PCr/ATP ratio and measures of body metabolic function. A total of 35 healthy women (56+/-14.0 years of age) underwent cardiac 31P magnetic resonance spectroscopy to assess PCr/ATP ratio - an index of cardiac high-energy phosphate metabolism. Fasting and 2-hour glucose levels were assessed using oral glucose tolerance test. Indirect calorimetry was performed to determine oxygen consumption and resting metabolic rate. There were no significant relationships between PCr/ATP ratio and resting metabolic rate (r=-0.09, p=0.62), oxygen consumption (r=-0.11, p=0.54), fasting glucose levels (r=-0.31, p=0.07), and 2-hour plasma glucose (r=-0.10, p=0.58). Adjusted analysis for covariates including age, body mass index, fat mass, and physical activity, had no significant influence on the relationship between PCr/ATP ratio and body metabolism. In conclusion, the lack of relationship between cardiac PCr/ATP ratio, glucose control and metabolic rate may suggest that overall metabolic function does not influence cardiac high-energy phosphate metabolism.

Dietary nitrate does not modify blood pressure and cardiac output at rest and during exercise in older adults: a randomised cross-over study.

Dietary nitrate (NO3-) supplementation has been associated with improved vascular and metabolic health. We conducted a double-blind, cross-over, placebo-controlled RCT to investigate the effects of 7-d consumption of beetroot juice compared with placebo on (1) blood pressure (BP) measured in resting conditions and during exercise, (2) cardiac and peripheral vascular function and (3) biomarkers of inflammation, oxidative stress and endothelial integrity. Twenty non-smoking healthy participants aged 60-75 years and BMI 20.0-29.9 kg/m2 were recruited. Measurement was conducted before and after each 7-d intervention period. Consumption of NO3- had no effect on resting systolic and diastolic BP. NO3- consumption did not improve indexes of central and peripheral cardiac function responses during cardiopulmonary exercise testing. Dietary NO3- supplementation did not modify biomarkers of inflammation, oxidative stress and endothelial integrity. This study does not support the short-term benefits of dietary NO3- supplementation on physiological and biochemical markers of vascular health in older healthy adults.

Bioreactance is a reliable method for estimating cardiac output at rest and during exercise.

BACKGROUND: Bioreactance is a novel noninvasive method for cardiac output measurement that involves analysis of blood flow-dependent changes in phase shifts of electrical currents applied across the thorax. The present study evaluated the test-retest reliability of bioreactance for assessing haemodynamic variables at rest and during exercise. METHODS: 22 healthy subjects (26 (4) yrs) performed an incremental cycle ergometer exercise protocol relative to their individual power output at maximal O2 consumption (Wmax) on two separate occasions (trials 1 and 2). Participants cycled for five 3 min stages at 20, 40, 60, 80 and 90% Wmax. Haemodynamic and cardiorespiratory variables were assessed at rest and continuously during the exercise protocol. RESULTS: Cardiac output was not significantly different between trials at rest (P=0.948), or between trials at any stage of the exercise protocol (all P>0.30). There was a strong relationship between cardiac output estimates between the trials (ICC=0.95, P<0.001) and oxygen consumption (ICC=0.99, P<0.001). Stroke volume was also not significantly different between trials at rest (P=0.989) or during exercise (all P>0.15), and strong relationships between trials were found (ICC=0.83, P<0.001). CONCLUSIONS: The bioreactance method demonstrates good test-retest reliability for estimating cardiac output at rest and during different stages of graded exercise testing including maximal exertion.

Ultra short-term heart rate recovery after maximal exercise in continuous versus intermittent endurance athletes.

This study tested the hypothesis that athletes participating in intermittent sports would exhibit a faster heart rate recovery (HRR) during the initial phase (<30 s) following maximal exercise than athletes participating in continuous endurance sports. Forty-six male athletes were allocated into continuous (CNT, n = 24) or intermittent groups (INT, n = 22), matched for age and aerobic fitness. Athletes performed maximal exercise on a treadmill using the ramp protocol. Immediately upon exercise cessation, subjects were placed supine with continuous measurement of HR during the first minute of recovery. Data were analyzed in 10-s intervals and compared between the groups. Repeated measures ANOVA showed a group x time interaction effects (p