The Effects of Mild Dehydration on Cycling Performance in the Heat

Abstract Introduction: Hypohydration exceeding 2% of body mass (bm), affected by heat and thirst level, leads to decreased athletic performance. Both physiological and psychological factors of dehydration have an impact on an athlete’s perceived performance. However, it is unclear whether the effects of psychological, physiological, or both have a negative impact on athletic performance caused by mild hypohydration. Purpose: The purpose of this study was to determine if mild hypohydration affects exercise performance in trained cyclists while blinding their hydration state. Methodology: Eleven competitive male cyclists participated in two blinded experimental trials, hypohydrated and euhydrated states by intra-venous infusions. The experimental criterium simulation test includes cycling through 3 sets of 20-minute steady state followed by a 5km race. Results: During the 5km time trial, the hypohydrated trial (39.0±0.5°C) resulted in significantly higher core temperatures compared to the euhydrated trial (38.5±0.2°C; P\u3c0.05). Cycling speed was significantly faster in the euhydrated vs. the hypohydrated trial (27.3±0.1 vs. 26.2±0.7 km×h-1; P\u3c0.05) due to greater cycling power output (304±6 vs. 286±10 W; P\u3c0.05). Conclusion: Overall, the study found that mild hypohydration led to impairment in exercise performance in the heat compared to euhydration, when subjects were unaware of their hydration state. These responses might have been a response of great heat strain and/or cardiovascular impairment

The influence of nutrient concentration on algal biomass and invertebrate communities in agricultural streams : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University, Palmerston North, New Zealand

High nutrient inputs have generally been identified as responsible for the degradation of lowland rivers and lakes in New Zealand and internationally. Nutrients have been shown to influence algal community growth rate and composition. In turn algae can have strong effects on invertebrate communities (density, richness, composition, distribution, structure and function). This study investigates the effect of nutrients on algal biomass and higher trophic levels to determine the importance of nutrient loading on stream ecosystems. Twenty six agricultural streams were surveyed in the Manawatu region in February, 2002. Algal biomass was greater in streams with high nitrate levels. Invertebrate communities differed in terms of the quantitative macroinvertebrate community index (QMCI), Ephcmeroptera, Plecoptera and Trichoptera (EPT) individuals and taxa between sites with high and low algal biomass. Regression analysis was used to relate the "quality" of the invertebrate community to stream algal biomass. At 13.μg/cm2 of chlorophyll a there was a dramatic shift in invertebrate community composition to more pollution tolerant taxa. In the Hawke's Ray region nutrient concentration was experimentally increased in 3 low order streams in the summer of 2002/2003. Increased nutrient concentration did not affect stream algal biomass. There were however changes in the proportions of EPT in the enriched community. I propose that these changes in EPT were in response to increased algal growth rates and constrained any increase in algal biomass. Therefore changes in landuse intensity may affect invertebrate community structure

Quantum phase transitions in the J-J' Heisenberg and XY spin-1/2 antiferromagnets on square lattice: Finite-size scaling analysis

We investigate the critical parameters of an order-disorder quantum phase transitions in the spin-1/2 $J-J'$ Heisenberg and XY antiferromagnets on square lattice. Basing on the excitation gaps calculated by exact diagonalization technique for systems up to 32 spins and finite-size scaling analysis we estimate the critical couplings and exponents of the correlation length for both models. Our analysis confirms the universal critical behavior of these quantum phase transitions: They belong to 3D O(3) and 3D O(2) universality classes, respectively.Comment: 7 pages, 3 figure

Effects of low level, low frequency electric fields on human reaction time

Low level, low frequency electric field effects on human reaction tim

Cardiovascular medication, physical activity and mortality: cross-sectional population study with ongoing mortality follow up

Objective: to establish physical activity levels in relation to cardiovascular medication and to examine if physical activity is associated with benefit independently of medication among individuals with no diagnosis of cardiovascular disease (CVD). Design: Cross-sectional surveys in 1998 and 2003 with ongoing mortality follow up. Setting: Household-based interviews in England and Scotland. Participants: Population samples of adults aged 35 and over living in households, respondents of the Scottish Health Survey and the Health Survey for England. Main outcome measure: Moderate to vigorous physical activity (MVPA) levels and CVD mortality. Results: Fifteen percent (N=3,116) of the 20,177 respondents (8,791 men); were prescribed at least one cardiovascular medication. Medicated respondents were less likely than those unmedicated to meet the physical activity recommendations (OR:0.89, 95%CI: 0.81 to 0.99, p=0.028). The mean follow up (±SD) was 6.6 (2.3) years. There were 1,509 any-cause deaths and 427 CVD deaths. Increased physical activity was associated with all-cause and CVD mortality among both unmedicated (all-cause mortality HR for those with ≥150 min/wk of MVPA compared with those who reported no MVPA): 0.58, 95%CI: 0.48 to 0.69, p<0.001) ; CVD mortality: 0.65, 0.46 to 0.91, p=0.036) and medicated respondents (all-cause death: 0.54, 0.40 to 0.72, p<0.001; CVD death: 0.46 (0.27 to 0.78, p=0.008). Conclusions: Although physical activity protects against premature mortality among both medicated and unmedicated adults, cardiovascular medication is linked with lower uptake of health enhancing physical activity. These results highlight the importance of physical activity in the primary prevention of CVD over and above medication