Impact of retrograde shear rate on brachial and superficial femoral artery flow-mediated dilation in older subjects

An inverse, dose-dependent relationship between retrograde shear rate and brachial artery endothelial function exists in young subjects. This relationship has not been investigated in older adults, who have been related to lower endothelial function, higher resting retrograde shear rate and higher risk of cardiovascular disease. Aim To investigate the impact of a step-wise increase in retrograde shear stress on flow-mediated dilation in older males in the upper and lower limbs. Methods Fifteen older (68±9 years) men reported to the laboratory 3 times. We examined brachial artery flow-mediated dilation before and after 30-minutes exposure to cuff inflation around the forearm at 0, 30 and 60 mmHg, to manipulate retrograde shear rate. Subsequently, the 30-minute intervention was repeated in the superficial femoral artery. Order of testing (vessel and intervention) was randomised. Results Increases in cuff pressure resulted in dose-dependent increases in retrograde shear in both the brachial and superficial femoral artery in older subjects. In both the brachial and the superficial femoral artery, no change in endothelial function in response to increased retrograde shear was observed in older males (‘time’ P=0.274, ‘cuff*time P=0.791’, ‘cuff*artery*time P=0.774’). Conclusion In contrast with young subjects, we found that acute elevation in retrograde shear rate does not impair endothelial function in older humans. This may suggest that subjects with a priori endothelial dysfunction are less responsive or requires a larger shear rate stimulus to alter endothelial function

Glycemic control during consecutive days with prolonged walking exercise in individuals with type 1 diabetes mellitus

Aims: Despite its general benefits for health, exercise complicates the maintenance of stable blood glucose concentrations in individuals with type 1 diabetes. The aim of the current study was to examine changes in food intake, insulin administration, and 24-h glycemic control in response to consecutive days with prolonged walking exercise (~8 h daily) in individuals with type 1 diabetes. Methods: Ten individuals with type 1 diabetes participating in the worlds' largest walking event were recruited for this observational study. Simultaneous measurements of 24-h glycemic control (continuous glucose monitoring), insulin administration and food intake were performed during a non-walking day (control) and during three subsequent days with prolonged walking exercise (daily distance 40 or 50 km). Results: Despite an increase in daily energy (31 ± 18%; p 10 mmol/L) and hypoglycemia (blood glucose 0.05 for all variables). The prolonged walking exercise was associated with a modest increase in glycemic variability compared with the control day (p < 0.05). Conclusion: Prolonged walking exercise allows for profound reductions in daily insulin administration in persons with type 1 diabetes, despite large increments in energy and carbohydrate intake. When taking such adjustments into account, prolonged moderate-intensity exercise does not necessarily impair 24-h glycemic control. © 2016 Elsevier Ireland Ltd

Dataset for: IMPROVEMENTS IN FITNESS ARE NOT OBLIGATORY FOR EXERCISE TRAINING-INDUCED IMPROVEMENTS IN CV RISK FACTORS

Objectives The purpose of this study was to assess whether changes in physical fitness relate to changes in cardiovascular risk factors following standardized, center-based and supervised exercise training programs in subjects with increased cardiovascular risk. Methods We pooled data from exercise training studies of subjects with increased cardiovascular risk (n=166) who underwent 8-52 weeks endurance training. We determined fitness (i.e. peak oxygen uptake) and traditional cardiovascular risk factors (body mass index, blood pressure, total cholesterol, high density lipoprotein cholesterol), before and after training. We divided subjects into quartiles based on improvement in fitness, and examined whether these groups differed in terms of risk factors. Associations between changes in fitness and in cardiovascular risk factors were further tested using Pearson correlations. Results Significant heterogeneity was apparent in the improvement of fitness and individual risk factors, with non-responder rates of 17% for fitness, 44% for body mass index, 33% for mean arterial pressure, 49% for total cholesterol and 49% for high-density lipoprotein cholesterol. Neither the number, nor the magnitude, of change in cardiovascular risk factors differed significantly between quartiles of fitness change. Changes in fitness were not correlated with changes in cardiovascular risk factors (all P>0.05). Conclusions Our data suggest that significant heterogeneity exists in changes in peak oxygen uptake after training, whilst improvement in fitness did not relate to improvement in cardiovascular risk factors. In subjects with increased cardiovascular risk, improvements in fitness are not obligatory for training-induced improvements in cardiovascular risk factors