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The purpose of this study was to assess the relationship of the heart rate deflection point (HRDP) to the ventilatory threshold (VT) in trained cyclists. Twenty-one endurance-trained cyclists (mean [+ or -] SD: V[O.sub.2]max = 67.6 [+ or -] 4.7 ml*kg*[min.sup.-1]) completed a maximal cycle ergometer test of volitional fatigue using a ramped protocol. Ventilatory variables (VE, V[O.sub.2], VC[O.sub.2]) and power were measured online with averages reported every 20 seconds. Heart rate (HR) was recorded every 20 seconds using a Polar monitor. VT was calculated using the excess C[O.sub.2] elimination curve. The first derivative of a logistic growth curve fit to the HR-power data produced the HRDP. No significant differences (p > 0.01) existed between HR values at HRDP (171.7 [+ or -] 9.6 b*[min.sup.-1]) and VT (169.8 [+ or -] 9.9 b*[min.sup.-1]) or between V[O.sub.2] values at HRDP (53.6 [+ or -] 4.2 ml*kg*[min.sup.-1]) and VT (52.2 [+ or -] 4.8 ml*kg*[min.sup.-1]). But power values at HRDP (318.7 [+ or -] 30.7 W) were significantly different (p < 0.01) from those at VT (334.8 [+ or -] 36.7 W). There were significant relationships between HRDP and VT for the physiological variables of HR (r = 0.92, p < 0.001), V[O.sub.2] (r = 0.72, p < 0.001), and power (r = 0.77, p < 0.001). These findings indicate that HR and V[O.sup.2] at HRDP are not significantly different from the values at VT in trained cyclists. HR values derived from HRDP may be used to set parameters for training intensity. Variability in the speed/ power-HRDP relationship across detrained/trained states may be used to evaluate training programs. Key Words: heart rate deflection point, ventilatory threshold, cycling, conconi, mathematical model

This article investigates the relationship between carbohydrate supplementation and distance swimming performance. An analysis of glucose metabolism, blood lactate, and heart rate measurements is presented.

The purpose of this study was to assess the difference in maximal physiological responses between an acute bout of deep-water running (DWR) and treadmill running (TMR) in young and older adults. Participants were 9 young and 9 older women who performed maximal DWR and TMR tests. Maximal measures included oxygen consumption (VO[sub 2max]), heart rate (HR[sub max]), ventilation (VE), respiratory-exchange ratio (RER), and blood lactate (BLac). The young women exhibited higher VO[sub 2max], HR[sub max], VE, and BLac than did the older women for both exercise conditions (p < .05). Lower VO[sub 2max], and HR[sub max] values were observed with DWR for both age groups (p < .05). No significant differences were found for VE, RER, and BLac in either group between exercise conditions, nor a significant interaction between exercise conditions or ages for any of the variables measured. The data suggest that although older adults exhibit lower maximal metabolic responses, differences between DWR and TMR responses occur irrespective of age. [ABSTRACT FROM AUTHOR]

Despite their size, small farm ponds are important features in many landscapes. Yet hydrographical databases often fail to capture these ponds, and their impacts on watershed processes remain unclear. For a 230-km2 portion of central Texas, United States ( U.S.), we created a historical inventory of ponds and quantified the accuracy of automated detection methods under varying drought conditions. In addition, we documented pond dredging/enlargement events and identified sites that had been abandoned. We also analyzed sediment cores from downstream reservoirs to track changes in watershed sediment transport. Over 75 years, pond densities increased more than 350% - to among the highest documented in the U.S. - and the ability of automated methods to detect these ponds was highly dependent on drought severity ( R2 = 0.96). Approximately 5% of ponds present in the 1950s were no longer present in 2012, while 33% were dredged between 1937 and 2012. Downstream reservoir sedimentation has decreased by an average of 55% as ponds have increased in number. These findings suggest that small ponds and the maintenance of trapping efficiency have large-scale impacts on sediment dynamics. Accurately accounting for these storage effects is vital to water resource planning efforts. [ABSTRACT FROM AUTHOR]

Woody plant encroachment-the conversion of grasslands to woodlands-continues to transform rangelands worldwide, yet its causes and consequences remain poorly understood. Despite this being a coupled human-ecological phenomenon, research to date has tended toward ecological aspects of the issue. In this paper, we provide new insight into the long-term relationships between human demographics and woody plant cover at the landscape scale. We used time-series aerial imagery and historical census data to quantify changes in population, land ownership patterns, and woody cover between 1937 and 2012 in three different settings in central Texas, USA. Woody cover closely paralleled population in a semi-urban watershed ( R2 = 0.81) and two separate clusters of rural watersheds ( R2 = 0.88 and 0.93), despite exhibiting very different directional trends over time in each setting. Woody cover also closely tracked average farm size in each rural watershed cluster ( R2 = 0.57 and 0.90). These results highlight a tight coupling between demographic trends and the extent of woody plant cover. Such human factors may explain a great deal of woody plant cover patterns in other global rangeland systems with similar historical contexts and serve as a predictive proxy of landscape trends. Accordingly, policy recommendations should consider these demographic factors, and future woody plant encroachment research should explicitly include human dimensions. [ABSTRACT FROM AUTHOR]