‘‘Beet-ing’’ the Mountain: A Review of the Physiological and Performance Effects of Dietary Nitrate Supplementation at Simulated and Terrestrial Altitude

Exposure to altitude results in multiple physiological consequences. These include, but are not limited to, a reduced maximal oxygen consumption, drop in arterial oxygen saturation, and increase in muscle metabolic perturbations at a fixed sub-maximal work rate. Exercise capacity during fixed work rate or incremental exercise and time-trial performance are also impaired at altitude relative to sea-level. Recently, dietary nitrate (NO3-) supplementation has attracted considerable interest as a nutritional aid during altitude exposure. In this review, we summarise and critically evaluate the physiological and performance effects of dietary NO3- supplementation during exposure to simulated and terrestrial altitude. Previous investigations at simulated altitude indicate that NO3- supplementation may reduce the oxygen cost of exercise, elevate arterial and tissue oxygen saturation, improve muscle metabolic function, and enhance exercise capacity/ performance. Conversely, current evidence suggests that NO3- supplementation does not augment the training response at simulated altitude. Few studies have evaluated the effects of NO3- at terrestrial altitude. Current evidence indicates potential improvements in endothelial function at terrestrial altitude following NO3- supplementation. No effects of NO3- supplementation have been observed on oxygen consumption or arterial oxygen saturation at terrestrial altitude, although further research is warranted. Limitations of the present body of literature are discussed, and directions for future research are provided

Reassessing the value of the exercise electrocardiogram in the diagnosis of stable chest pain

Background: doubt has been expressed about the value of exercise electrocardiography (ECG) in the diagnosis of coronary artery disease (CAD). This paper tests the diagnostic impact of 2 strategies for analysing ST segment depression. Methods: 7739 consecutive patients referred to a rapid access chest pain clinic from primary care between January 1999 and March 2010 were studied. The pre-exercise probability of coronary artery disease (pCAD) was determined from symptoms and risk factors using the methodology of the UK National Institute for Health and Clinical Excellence (NICE). The post-exercise pCAD was calculated: firstly, using NICE’s sensitivity of 67% and specificity of 69% for the exercise ECG, and secondly using a published set of 6 sensitivities and specificities that vary according to the amount of ST segment shift on exercise. Pre- and post-exercise pCADs were grouped according to NICE’s categories: CAD ruled out, suitable for non-invasive testing, candidate for coronary arteriography, and CAD ruled in. Results: 2910 of the 5157 patients exercised were in the ‘suitable for non-invasive testing’ category. With NICE’s single combination of sensitivity and specificity, 793 (27.3%) of the 2910 had CAD ruled out and 128 (4.4%) became candidates for coronary arteriography. With 6 combinations of sensitivity and specificity, 1383 (47.5%) of the 2910 had CAD ruled out and 48 (1.6%) CAD ruled in, while another 170 (5.8%) became candidates for coronary arteriography. Conclusion: the exercise ECG has considerable diagnostic value if it is assumed that the greater the ST segment shift the greater the likelihood of CAD.Published versio