Ramos J.S.,University of Queensland |
Dalleck L.C.,Western State Colorado University |
Tjonna A.E.,Norwegian University of Science and Technology |
Beetham K.S.,University of Queensland |
Coombes J.S.,University of Queensland
Sports Medicine | Year: 2015
Background: Vascular dysfunction is a precursor to the atherosclerotic cascade, significantly increasing susceptibility to cardiovascular events such as myocardial infarction or stroke. Previous studies have revealed a strong relationship between vascular function and cardiorespiratory fitness (CRF). Thus, since high-intensity interval training (HIIT) is a potent method of improving CRF, several small randomized trials have investigated the impact on vascular function of HIIT relative to moderate-intensity continuous training (MICT). Objective: The aim of this study was to systematically review the evidence and quantify the impact on vascular function of HIIT compared with MICT. Methods: Three electronic databases (PubMed, Embase, and MEDLINE) were searched (until May 2014) for randomized trials comparing the effect of at least 2 weeks of HIIT and MICT on vascular function. HIIT protocols involved predominantly aerobic exercise at a high intensity, interspersed with active or passive recovery periods. We performed a meta-analysis to compare the mean difference in the change in vascular function assessed via brachial artery flow-mediated dilation (FMD) from baseline to post-intervention between HIIT and MICT. The impact of HIIT versus MICT on CRF, traditional cardiovascular disease (CVD) risk factors, and biomarkers associated with vascular function (oxidative stress, inflammation, and insulin resistance) was also reviewed across included studies. Results: Seven randomized trials, including 182 patients, met the eligibility criteria and were included in the meta-analysis. A commonly used HIIT prescription was four intervals of 4 min (4 × 4 HIIT) at 85–95 % of maximum or peak heart rate (HRmax/peak), interspersed with 3 min of active recovery at 60–70 % HRmax/peak, three times per week for 12–16 weeks. Brachial artery FMD improved by 4.31 and 2.15 % following HIIT and MICT, respectively. This resulted in a significant (p < 0.05) mean difference of 2.26 %. HIIT also had a greater tendency than MICT to induce positive effects on secondary outcome measures, including CRF, traditional CVD risk factors, oxidative stress, inflammation, and insulin sensitivity. Conclusion: HIIT is more effective at improving brachial artery vascular function than MICT, perhaps due to its tendency to positively influence CRF, traditional CVD risk factors, oxidative stress, inflammation, and insulin sensitivity. However, the variability in the secondary outcome measures, coupled with the small sample sizes in these studies, limits this finding. Nonetheless, this review suggests that 4 × 4 HIIT, three times per week for at least 12 weeks, is a powerful form of exercise to enhance vascular function. © 2015, Springer International Publishing Switzerland.
Perkins D.W.,Western State Colorado University |
Scott M.L.,Utah State University
River Research and Applications | Year: 2015
River regulation is associated with vegetation encroachment and invasions of some non-native species in the semi-arid west. Shifts in the abundance of native and non-native woody riparian species are an interplay of regulation, life history traits and an array of flow and physical environmental variables. We sought to compare plant densities and per cent cover of several invasive species over two time periods in a paired river study, contrasting three different degrees of regulation along reaches of the Green and Yampa rivers in Colorado and Utah, USA. We censused patches of non-native plants and recorded per cent cover in quadrats along 171river km. The upper Green (10.1patchesha-1) had the highest invasive plant patch density followed by the lower Green (4.4 per ha) and the Yampa (3.3 per ha). Invasive species were present in 23%, 19% and 4% of sample quadrats, and an average of 0.28, 0.22 and 0.04 invasive species detected per square metre was recorded along the upper Green, lower Green and Yampa Rivers, respectively. Most species had significantly (p≤0.02) higher percent cover on the upper Green than either or both the lower Green and the Yampa River. Whereas the less regulated river reaches maintain lower densities of invasive species than the most regulated reach, long-term persistence of this pattern is still in question as some species patches showed notable increases on the Yampa and lower Green Rivers from 2002-2005 to 2010-2011. Although invasion is enhanced by flow regulation, life history traits of some species suggest invasion is likely, regardless of flow regulation. Published 2015.
Petrie E.S.,Western State Colorado University |
Evans J.P.,Utah State University |
Bauer S.J.,Sandia National Laboratories
AAPG Bulletin | Year: 2014
The sedimentologic and tectonic histories of clastic cap rocks and their inherent mechanical properties control the nature of permeable fractures within them. The migration of fluid through mm- to cm-scale fracture networks can result in focused fluid flow allowing hydrocarbon production from unconventional reservoirs or compromising the seal integrity of fluid traps. To understand the nature and distribution of subsurface fluid-flow pathways through fracture networks in cap-rock seals we examine four exhumed Paleozoic and Mesozoic seal analogs in Utah. We combine these outcrop analyses with subsidence analysis, paleoloading histories, and rock-strength testing data in modified Mohr-Coulomb-Griffith analyses to evaluate the effects of differential stress and rock type on fracture mode. Relative to the underlying sandstone reservoirs, all four seal types are low-permeability, heterolithic sequences that show mineralized hydraulic-extension fractures, extensional-shear fractures, and shear fractures. Burial-history models suggest that the cap-rock seal analogs reached a maximum burial depth >4 km (2.5 mi) and experienced a lithostatic load of up to 110 MPa (15,954 psi). Median tensile strength from indirect mechanical tests ranges from 2.3 MPa (334 psi) in siltstone to 11.5 MPa (1668 psi) in calcareous shale. Analysis of the pore-fluid factor (λv = Pf/σv) through time shows changes in the expected failure mode (extensional shear or hydraulic extension), and that failure mode depends on a combination of mechanical rock properties and differential stress. As expected with increasing lithostatic load, the amount of overpressure that is required to induce failure increases but is also lithology dependent. Copyright © 2014. The American Association of Petroleum Geologists. All rights reserved.
Chapin F.S.,University of Alaska Fairbanks |
Knapp C.N.,Western State Colorado University
Environmental Science and Policy | Year: 2015
This article identifies opportunities and challenges to using sense of place as motivation for long-term stewardship at multiple spatial scales in a rapidly changing world. Sense of place reflects processes by which individuals or groups identify, attach to, depend on, and modify places, as well as the meanings, values, and feelings that individuals or groups associate with a place. These associations with place are fluid through time as they are felt, imagined, interpreted, and understood. Sense of place appears to most strongly motivate stewardship actions at local scales under circumstances where people value a place for the same reasons, and the conditions of the place are deteriorating. We suggest that well-recognized actions that build place attachment could create a reservoir of potential stewardship, if locally valued places were to deteriorate, as, for example, in response to climate change. Sense of place does not always promote stewardship, however, because attitudes may not lead to actions, some actions do not promote sustainability, and different place identities in the same place may lead to different stewardship goals (e.g., conservation vs. development). In situations where sense of place is deeply contested, we suggest that stewardship is best fostered by transparent and respectful dialogue to identify shared values and concerns and negotiate areas of disagreement. As a result of increased human mobility and globalization, individuals interact with many places to satisfy their desires and needs. We suggest that this opens new opportunities to motivate stewardship of types of places at regional, national, and global scales. Approaches such as discourse analysis, boundary concepts, incompletely theorized agreement, and common property theory that explicitly address contested concepts might contribute significantly to fostering sustainability in a rapidly changing and deeply divided world. © 2015 Elsevier Ltd.
Nolan P.B.,University of Auckland |
Beaven M.L.,University of Auckland |
Dalleck L.,Western State Colorado University
International Journal of Sports Medicine | Year: 2014
We sought to determine the incidence of 'true' VO2max confirmation with the verification procedure across different protocols. 12 active participants (men n=6, women n=6) performed in random order 4 different maximal graded exercises tests (GXT) and verification bout protocols on 4 separate days. Conditions for the rest period and verification bout intensity were: A - 105% intensity, 20 min rest; B - 105% intensity, 60 min rest; C - 115% intensity, 20 min rest; D - 115% intensity, 60 min rest. VO2max confirmation (difference between peak VO2 GXT and verification trial<±3%) using the verification trial was 12/12 (100%), 12/12 (100%), 8/12 (66.70%), and 7/12 (58.33%) for protocols A, B, C, and D. There was a significant (p<0.05) effect of verification intensity on VO2max confirmation across all exercise test conditions (intensity effect within recovery 20 min (χ2 (1)=4.800, p<0.05), intensity effect within recovery 60 min (χ2 (1)=6.316, p<0.05)). No significant effect was found for incidence of VO2max confirmation with different rest periods. We recommend the use of 105% of the maximal GXT workload and 20 min rest periods when using verification trials to confirm VO2max in normally active populations.