‘‘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

Is Overwinter Mortality Commonplace in Delaware Bay Oyster Populations? The Ambiguity of Dredge Efficiency

A series of fall surveys and spring resurveys from 2005 to 2010 were examined to determine whether overwinter mortality was a common occurrence in oyster populations from Delaware Bay. Box counts tended to be lower in the spring more often than expected by chance. Occasionally, counts of live oysters also declined. A proportionately larger reduction in dredge efficiency during the winter for boxes compared with live oysters was judged the most likely reason, rather than disarticulation of boxes. Little evidence for overwinter mortality was found; however, reefs in the center of the salinity range exhibited a larger decrease in live oysters than boxes in the spring resurvey. This happenstance provided the only evidence for overwinter mortality that could be distinguished above the countervailing trend provided by the decline in catchability of boxes that frequently occurred. Before ascribing variations in population descriptors during the winter to biological processes, the alternative of an overwinter change in the efficiency of the sampling gear must be excluded